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How would exhaust heat recovery into the combustion chamber affect the efficiency of a jet engine? So, a jet engine basically sucks in air, heats it up and spits it out, right?The hotter the air gets, the faster the exhaust velocity and thus the more efficient (Higher specific impulse). Now my question is how this all gets affected if you use a heat recovery system, either a heat pump or a simple heat exchanger. Let's ignore the annoying practicalities of metals melting and all that stuff and just look at the theoretical side. If you recover heat from the exhaust and put it back into the combustion chamber how does this affect the efficiency of the engine? If we were to apply the heat into the combustion chamber using a heat pump, pumping heat from the exhaust into the chamber could we get even higher efficiencies? While "Yes/No" answers would suffice I would be much more interested in a thermodynamic explanation and possibly even some estimations of the theoretical efficiency which could be reached using the Carnot cycle for pumping the heat. Onto the practical, has anything like this been experimented with? To my knowledge we don't have heat pumps capable of operating at 2000 degrees Celsius and pumping heat quickly enough to compare to any type of engine, but maybe someone has experimented with simple heat exchangers like how rocket engines use regenerative cooling (for different purposes though, but still similar to this). <Q> Extracting heat from the exhaust will cool and compress it, slowing it down and reducing thrust. <S> Recirculating the heat back into or downstream of combustion will raise the temperature at that point and on downstream to the extraction point. <S> The inevitable thermodynamic losses mean that the returned heat does not quite compensate for the heat drawn out and overall efficiency will fall a little. <S> What does improve efficiency is to draw through additional air mass in order to increase the exhaust mass flow, even at the expense of lower overall velocity and temperature. <S> This is what the bypass turbofan does. <S> A more radical modification is to swap the combustion chamber for a heat exchanger and heat the gas via hot fluid from an external source; the hotter the fluid the better. <S> I have seen this proposed for the hydrogen turbopump in some versions at least of the SABRE air-breathing rocket engine. <S> It was also proposed for nuclear-powered bombers in the 1950s, though I cannot recall if those included turbojets as well as ramjets. <A> A couple of remarks: <S> The reaction jet engine produces thrust in the exhaust nozzle. <S> In a subsonic engine the exhaust gas first accelerates in the convergent section of the nozzle then it expands in the divergent section. <S> Expanding, the gas looses not only kinetic energy <S> but it cools down as well. <S> There is a reactive jet engine that uses heat exchanger. <S> Is called Sabre and the developer tried to solve the problem of suborbital flight using one engine only. <S> At takeoff the engine functions as a reaction jet. <S> Once the speed exceeds the range of usability of the axial compressor, then a heat exchanger placed in the air intake cools down the air to maintain the efficiency of the axial compressor even at supersonic speeds. <S> The airflow through the engine remains subsonic. <S> However, on exhaust the afterburner provides the extra thrust required to maintain speeds in the vicinity of Mach5 to 7. <S> This engine burns hydrogen and uses liquid helium as coolant, or so the developer says. <S> This is a bold undertaking from a private developer. <S> To answer your question: The Sabre is an example of using a heat exchanger in the air intake. <S> The only cooling in the exhaust is meant to keep the hot side operational and not to extract energy from exhaust gas because that will affect the thrust. <A> Theoretically, in an infinitely efficient system, there would be no net difference. <S> The energy lost in the exhaust would be added back to the combustion chamber to be lost again in the exhaust. <S> Maybe, you could use this heat exchange side engine to run another system without losing engine power. <S> But, there is never something for nothing. <S> Although I've read that the cowled radiator for the piston engine spitfire did produce a small amount of thrust as a biproduct. <S> This is all predicated by the fact that the heat energy is dumped back into the whole system in or after the combustion chamber. <S> If it's before the the compressors, it would lower the density of the air coming in. <S> Your thrust is based on the mass of the air being accelerated. <S> If it dumped into the compressors, that energy may be lost to the peak amount that the compressors can increase density and pressure. <S> It would be lost in the current way compressors shed excess heat. <S> If the compressors could be made of material that did not need to be protected from excess heat, then there would be no need for the heat exchanger adding heat. <S> It would already be there as a biproduct of compression. <S> Therefore, you would not need to rob it from the exhaust.
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Since the thrust is developed in the last section of the nozzle then having a heat exchanger further down would actually reduce the thrust by reducing the ability of the gas to expand.
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How do SIDs work in New York City? I've started working to make airport files for an online ATC game, and my first airport is Newark Liberty (DP: https://flightaware.com/resources/airport/KEWR/DP/all/pdf ). What I already understand is that there are various climbs valid for different runways, and that the SID directs each aircraft to its first fix. What I don't understand is how the climb is determined for each aircraft. I also want to know how often airplanes use the SIDs, as I sometimes see planes on Flightradar not following the climb paths. Thanks, this has confused me for a week or two. <Q> The LIB4 and EWR4 SIDs, and others like them with just a bunch of VORs, are designed to give ATC maximum flexibility and assume radar vectors . <S> Basically, you take off, make a turn or two to get clear of the airport (and any low obstacles), and then ATC will vector and climb you based on conflicts with other planes at that moment , so you'll probably never get the same instructions twice. <S> There is no real plan; it's literally made up on the spot by each controller for each plane. <S> The PORTT4 (RNAV) SID is completely different: you have various specific routes to follow and detailed climb plans for each. <S> Many such arrivals and departures in an area will be carefully designed to never conflict with each other (the top and bottom altitudes listed usually indicate there's another SID/STAR crossing 1000ft above/below at that point), so ATC just watches to make sure everyone follows the plan—and gives out shortcuts when possible. <S> Unfortunately, that SID is only valid for two of the six runways, though presumably they're the ones used most often. <S> Note the latter's lost comms procedure is just to follow the charted plan you're expecting to follow anyway, <S> though without any shortcuts, whereas the former has an entirely different (and uncharted) plan that you'd probably never follow otherwise. <A> The various climbs are usually determined by noise abatement interests and other stakeholders. <S> You will find that some departures can be quite complex. <S> I cannot say anything to aircraft, that don’t follow the SIDs, they are there for a reason. <S> Maybe those are aircraft at cruising altitude passing over the aerodrome? <A> The climb on a SID is determined based on the minimum climb needed to clear obstacles in the departure as well as aircraft performance. <S> Passenger comfort also comes into play. <S> Typically a pilot will follow at least the minimum requirements published on a SID unless otherwise directed by ATC. <S> If a pilot’s aircraft cannot match the performance requirements of the SID, they should notify ATC prior to departure that they are unable and request a different DP their aircraft can comply with. <S> For heavy transports departing busy airports, a SID or an OCD will almost always be used. <S> Light aircraft ie GA reciprocating and non transport category turboprops may make use of a SID - though some SIDS are restricted to turbojet aircraft only - and, at a bare minimum, a OCD is recommended in the case of marginal weather. <S> Pilots operating in IFR may opt out of flying a SID by placing a “no SID” comment in the remarks section of their IFR flight plan.
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SIDs are created by the FAA or the individual operators and used by aircraft departing from airports to streamline the flow of traffic departing that location to their transition into the enroute structure ie establishing on low or high altitude airways.
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What is the phraseology when leaving a TRSA? When leaving TRSA what is the correct phraseology to tell ATC that radar service is no longer desired? <Q> You can say "cancel radar service" (probably the most standard under ICAO), "cancel flight following," "request frequency change," or anything else that conveys the same general idea. <S> If all else fails, plain English is always acceptable too. <S> Regardless of which you say, ATC's response should be "radar service terminated, squawk VFR, frequency change approved," same as in any other class E airspace. <A> On takeoff, tower will typically tell you to contact approach as you start your climb. <S> After you do that, and if VFR and not on flight following, you just report "Binghamton approach, Nxxxxx is clear to the east" as an example, and can add your altitude. <S> Binghamton, NY TRSA is the nearest one I fly thru with any sort of regularity (couple times a year). <S> Basically you can treat them like a Class C as the TRSA is likely to be centered around a towered airport, while Class D may or may not be. <S> If you ask for flight following prior to takeoff, Gnd control, or the tower, can set you up with a squawk code so that approach has you in the system already when you contact them. <S> I always use flight following when flying cross country, nice to have another set of eyes looking out for you, and it expedites handoff to Center, or the next approach control, depending on where you are. <S> We're also under a Class B shelf, so it can be busy. <S> There are still planes without ADS-B, some illegally, some not needing it due to staying out of radio required airspace, or due to not having electrical systems, so all due diligence helps. <A> There is recommended verbiage per AIM 4-1-18-b.2: <S> If any aircraft does not want the service, the pilot should state “negative TRSA service” or make a similar comment, on initial contact with approach control or ground control, as appropriate. <S> In the United States, participation in radar services such as flight following by VFR traffic is not mandatory. <S> It is recommended for pilots flying VFR as a non-regulatory service. <S> Two-way communication for VFR traffic before entering and while within Class B, C & D airspace, and within 4 miles of a towered airport below 2500 feet AGL, is still required. <S> Outside of these areas, communication with ATC by non-participating VFR traffic is optional only. <S> This also applies to airspace within the TRSA <S> (communication with the underlying Class D is still required). <S> Communication rules for IFR still apply to IFR traffic regardless. <S> There is no mandatory phraseology for the pilot. <S> No reason has to be given. <A> According to ICAO DOC 444 12.4.1.10: <S> RADAR SERVICE TERMINATED DUE (instructions) <S> (reason).
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If you are already participating in radar services like flight following as VFR, you can ”cancel” ”terminate” or ”discontinue” the service in plain English.
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How does latitude affect the air temperature at 8 km altitude where planes fly? Is the air temperature (at 8km) above the North or South poles colder than the same altitude above the equator? Why? Ground level air temperature difference between coldest and warmest places on Earth can be >70C. As you get higher, the temperature drops, of course. Does it mean that near Arctic circle air temperature at let's say, 8km altitude still maintains approximately the same difference with the 8km altitude above equator as at the ground level? Or does it even out? Is it perhaps even possible to have air at some altitude significantly warmer than at ground level? <Q> In the troposphere, air at altitude is colder than air at ground level. <S> From the wiki article on troposphere (I added the bullet points): <S> The troposphere is heated from below by latent heat, longwave radiation, and sensible heat. <S> Surplus heating and vertical expansion of the troposphere occurs in the tropics. <S> At middle latitudes, tropospheric temperatures decrease from an average of 15 °C (59-degree Fahrenheit) at sea level to about −55 °C (-67-degree <S> Fahrenheit) at the tropopause. <S> At the poles, tropospheric temperature only decreases from an average of 0 °C (32-degree Fahrenheit) at sea level to about −45 °C (-49-degree <S> Fahrenheit) at the tropopause. <S> At the equator, tropospheric temperatures decrease from an average of 20 °C (68-degree <S> Fahrenheit) at sea level to about −70 to −75 ° <S> C (-94 to -103-degree Fahrenheit) at the tropopause. <S> The troposphere is thinner at the poles and thicker at the equator. <S> The average thickness of the tropical troposphere is roughly 7 kilometers greater than the average tropospheric thickness at the poles. <S> There is quite a bit of variation in the troposphere as a function of place on earth, and much effort has been put into creating a standardised atmosphere that can be used for practical purposes around the world. <S> The ICAO standard atmosphere serves that purpose. <S> It cannot account for local wind conditions and humidity. <S> I found a graph in an old paper format uni book on the atmosphere, depicting average conditions in two separate places on earth, Berlin and 40° latitude in North America. <S> The graph shows that although the temperature lapse rate is very similar in both cases, there is a difference in temperature at a given height. <S> The arrow gives the temperature difference at 8 km height, also transported to 0 m (less average difference) and to 10 km (more average difference). <S> Above is for average temperature at two different places on earth, at similar latitudes. <S> I could not find any direct comparison between average temperature at altitude of the poles and the equator - the wiki article seems to indicate that average temperature at the poles is higher at high altitude, a surprising indicat <A> The temperature decreases at approximately 3.57 degree Fahrenheit per 1000', the adiabatic lapse rate, until hitting the tropopause , the boundary between the troposphere (lower altitudes) and the stratosphere. <S> At that point the temps flatten out. <S> The lapse rate is pretty constant everywhere, so yes, it should be colder at higher latitudes for the same altitude. <S> But... <S> The tropopause is at a higher altitude at lower latitudes, so you actually end up with cooler temps above the equator then above the poles for very high altitudes (17 km range). <A> The airplanes do not cruise at a certain altitude, but at a certain pressure level. <S> That could be an irrelevant nitpick if the temperature did not directly affect the pressure as a function of altitude. <S> But it does (through the hydrostatic equilibrium). <S> In colder areas the air is heavier and flight levels are lower as can be seen in maps of geopotential height <S> At FL360 the pressure is 225 hPa and the altitude is around 36 thousand feet. <S> The 300 hPa and 250 hPa will be quite typical flight levels for airliners (~FL300 and FL340). <S> You can see the current map of altitudes and temperatures for these and other levels at http://weather.uwyo.edu/upperair/uamap.shtml <S> For example: http://weather.uwyo.edu/cgi-bin/uamap?REGION=nh&OUTPUT=gif&TYPE=an&LEVEL=300&date=2020-01-09&hour=0 <S> The green numbers are temperatures, the blue numbers are altitudes. <S> You can see that for the same flight level the aircraft is at 9600 m above North Africa or Florida and at 8400 m near the north pole in the current weather. <S> In summer the air is warmer and the flight levels are higher as you can easily see by choosing a different date in the app. <S> Also, the south-north gradient is weaker in summer - related to the strength of the polar vortex. <S> Due to the air compressibility you can never have higher temperatures in the stratosphere than at the Earth surface. <S> However, in certain sense, the air at higher levels IS actually warmer. <S> The potential temperature is higher and if the air is brought to the surface pressure level, it will be indeed warmer. <S> However, that costs mechanical energy (work).
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But surprisingly, air at altitude at the poles can be warmer than air at altitude at the equator.
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Can a wing generate lift in excess of its aircraft's weight? "For a plane or bird to fly, its wings must produce enough lift to equal its weight. " I got that excerpt from " https://www.sciencelearn.org.nz/resources/300-wings-and-lift ". My questions:(1) Can an aircraft wing create lift that is greater than the weight of the aircraft?(2) If the answer to question (1) is yes, then what happens in such a situation? <Q> Yes, otherwise airplanes would be unable to go upwards into the sky. <A> As with any "unbalanced" force, this will result in an acceleration of the airplane in the direction of the lift, according to Newton's Second law. <S> $$\mathbf F=m~\mathbf <S> a$$ <S> Please note, the entities in bold face are vector quantities. <S> This is what happens during any positive $\mathrm G$ maneuver, like a pullout from a dive, a loop, etc. <A> Furthermore to @Zeiss' answer, whenever an aircraft is steady-state banked, the lift will be greater than its weight. <S> However, its speed will be constant; instead, the acceleration is centripetal and results in a circular turn. <S> Edit, clarification on pull up maneuver : When an aircraft is pitched up via pitch control, and after the short-period mode settles (a few seconds at most), it will gain a lift imbalance greater than its weight due to higher angle of attack (AOA). <S> Similar to a banked turn, since the net force is perpendicular to the horizontal velocity, it will be centripetal and results in a vertical circular motion. <S> This is the early stage of the maneuver. <S> Since a higher AOA has higher drag, the airspeed will decay toward a new and lower trim speed. <S> At the same time, as airspeed decreases, the net lift also decreases, so there is less force imbalance. <S> As the decreasing airspeed undershoots the new trim speed, the aircraft will pitch down again. <S> This cyclical exchange of energy is called phugoid and usually persists for a while (dozens of minutes to an hour) if left unchecked. <S> Eventually, however, the phugoid dies down (phugoid is usually stable in non-transonic regime) and the airplane is flying at the new trim speed, with lift equal to weight once again. <S> If the airplane is in the front of the power curve , it will climb at steady-state; otherwise, it will descend. <A> A kite is a simple aircraft, generating lift. <S> The vertical component of the pull you feel on the string is any resultant lift greater than the weight of the aircraft, the horizontal component being the drag. <S> In a non-tethered aircraft, excess lift causes the aircraft to "rise", or more precisely, causes the flight path to curve upwards. <A> The lift a wing CAN generate is a design feature of the wing. <S> The lift a wing does generate is a feature of the weight and the flight path of the aircraft.
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Yes, a wing can (given sufficient forward speed and angle of attack) generate lift greater than the weight of the aircraft.
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Are jet engines designed in a way to make an explosion result in the least damage possible? I know most engines are super reliable today, but do manufacturers do anything to at least make an explosion result in the least damage possible? <Q> The most (kinetic) energy is in the fan and turbine blades and disc. <S> The engine is enclosed in a containment chamber whose purpose it is to protect the rest of the airplane from shrapnel in case of a fan disc or fan blade failure. <S> Here's a video of a test where a fan blade failure is simulated: As you can see, the fan blade more or less completely destroys the engine, but no debris or shrapnel leaves the containment chamber. <S> Unfortunately, the turbine disc and blades have too much energy to be realistically containable. <S> (In other words: the required shielding would be too thick and heavy.) <S> Engine failures where debris or shrapnel is able to leave the containment chamber is called an uncontained engine failure , and they are very rare, but they still do happen. <S> Since it is impossible to contain a turbine blade or disc failure, risks are mitigated in different ways, e.g. by requiring regular, very detailed inspections and extremely tight tolerances. <A> The main place engine manufacturers will focus on minimizing damage is with the large fan at the front of a turbofan engine. <S> FAA Advisory Circular 33-5 discusses the regulations that cover this. <S> The manufacturer must show that the worst case blade rotating at the highest RPM can successfully be contained. <S> Only 15 seconds after the event is the operator allowed to adjust engine controls. <S> The engine and related structure must also be able to withstand the resulting imbalance for the rest of the flight, especially for ETOPS certification. <S> While the windmilling engine will produce drag, the aircraft will still remain controllable. <S> However, an engine failure is an extremely dynamic event, dissipating large amounts of energy. <S> It's up to the aircraft manufacturer to ensure the engines do not pose a threat to safety of flight in the event of an uncontained engine failure. <S> FAA Advisory Circular 20-128A discusses some of the methods on minimizing the hazards of an uncontained engine failure on the airplane. <S> Below is a figure from this document showing typical locations of systems in the fuselage. <S> Each critical system will have redundancy, and is routed such that debris from an engine failure cannot damage enough systems to prevent safety of flight. <S> Below, tail mounted engine is shown, plotting debris paths versus systems locations. <S> The FAA also published a report on Large Engine Uncontained Debris Analysis . <S> This report is full of statistics and photos of damage caused by uncontained engine failures. <S> Analysis considers the size of the debris involved, the speed at which it impacts other structure, and relative angles between the debris and impact surface. <S> One of the most critical systems to protect in a twin-engine airplane is the remaining engine. <S> Manufacturers have also sought patents on ways of tilting the engines to keep them out of each other's debris paths. <S> New technologies such as open rotor fans present additional challenges to protect the aircraft from a blade failure, as there is no fan case to contain them. <A> A jet engine may not contain a severe explosion (for whatever reason) but there are various mandated things that are put in place to help protect the airframe. <S> The engines are generally mounted such that they shear off cleanly and away from the airframe. <S> There are a few AC's like this one and this one that discuss how to deal with and comply with various safety regulations around unconfined blade failure and unconfined rotor failure, as well as this one about pylon loading. <S> Jets are generally produced to a very high standard to prevent issues from happening in the first place which is in a way a safety consideration. <A> Cowlings can be designed to contain fan failures but if the core comes apart you have some pretty high velocity shrapnel coming out that nothing short of quarter inch armour plate will stop. <S> The main design feature you typically see to mitigate burst risk is the placement of cable runs and hydraulic runs, where there are redundant runs, spaced apart in the fuselage to reduce this risk of shrapnel taking out all of the cable runs from a burst (as happened with that <S> DC-10 all those years ago, because they were forced to run right next to the tail engine to get to the fin). <S> You might also see strategically placed armour plates located between a cable run and the turbine disc, where a single run is critical for safety. <S> Beyond that, control of risk is mostly about maintenance and inspection of the components, same as with things like primary structure. <S> When turbine bursts happen it's usually because of some microscopic manufacturing flaw in the disc that went undetected and falls into the random s-- <S> t happens category. <S> As I like to say, it's a dangerous world for everybody but rocks.
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Shielding may be required to prevent debris from one engine from crossing over and damaging critical parts of the other engine.
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Why are primary and supportive instruments in instrument flying different depending on the phase of flight? For example, in straight-and-level flight, the power's primary instrument is the Air Speed Indicator (ASI), and the supportive are the engine instruments. In another example, straight constant-airspeed climb, the primary are engine instruments, and the supportive is the ASI. Why does the primary instrument change? <Q> In straight and level flight, the heading indicator provides more relevant bank information as it tells you whether your current bank attitude is maintaining the desired heading. <S> The altimeter is providing the most relevant pitch information as it’s telling you whether your current pitch will maintain the correct altitude. <S> The airspeed indicator is the best indication for your required power as it’s telling you if the current power settings will maintain the desired airspeed. <S> Other instruments provide supporting information. <S> Here in straight and level flight the attitude indicator provides good supporting bank and pitch indications, the VSI provides supporting pitch information, etc. <S> Supporting instruments change to primary instruments in certain maneuvers and vice versa. <S> And, incidentally, in a established constant airspeed climb, your primary for bank is <S> the heading indicator and your primary for pitch is the airspeed indicator. <S> Primary for power is either the tachometer, manifold pressure, torque, or fan speed gauges, depending on the aircraft you are flying. <S> Typically you would set to maximum continuous power in a light airplane for this situation. <A> The whole point of classifying primary or secondary instrument (or the other method control-performance) is to teach pilots to look at what is important during different phases of flight. <S> When you read the Instrument Flying Handbook , it will tell you what instruments are primary and what instruments are secondary. <S> For example, in straight and level flight, the altimeter is primary for pitch, the airspeed is primary for power, and the turn and bank indicator is primary for bank. <S> If you examine what these instruments are doing at this exact moment, none of those instruments should be moving... <S> they are constant. <S> Hence, the primary characteristic of primary instruments are they are constant. <S> Secondary instruments for straight and level flight are the VSI for pitch, power for airspeed and attitude indicator for bank. <S> These instruments show you how to control the airplane to return to the aircraft flight attitude you had before. <S> For example, you notice the airspeed start slowing. <S> You take a look at the secondary instrument, power and notice that it has slowly backed off. <S> Increasing power should then cause the airspeed to return to normal. <S> Hence, the primary characteristic of secondary instruments are they show trends. <S> Reading the manual, you will also discover that anytime you change the pitch or bank of the airplane you should look at the attitude indicator. <S> It is primary instrument for all changes in the flight attitude of the airplane. <S> For example, if you want to change between straight and level to a constant airspeed climb, you will use the attitude indicator to set the pitch attitude and then verify the airspeed is climbing at the correct speed. <A> The answers already provided are very good, this answer is meant to say the same thing in different terms, not to contradict what has already been written. <S> A primary instrument is one that provides a value for you to hold . <S> If you want to maintain 5,000 feet, then the altimeter is the primary instrument because though there are other instruments that can tell you about your altitude, the altimeter is the only one that can show you what your altitude is . <S> Similarly, when entering a climb, the attitude indicator is primary for pitch, because you should be setting a particular pitch and the attitude indicator is where you look to see what degree of pitch you have. <S> Primary instruments give you a target, supporting instruments help you hit it. <A> All the answer except for quiet flyer's are spot on. <S> Although, I do appreciate, acknowledge and understand his point of view. <S> 90 years of instrument flight has dictated which instrument is primary and which is secondary for each state of flight. <S> It is not arbitrary. <S> The way to look at it is that you are trying to achieve a certain outcome without the benefit of your usual feedback. <S> You can not rely on on sight, sound (in some cases), touch (seat of the pants), or sense of motion and balance. <S> Say for instance, if you are flying IMC. <S> And, you want to fly straight and level in unaccelerated flight. <S> The Airspeed Indicator is your primary for power because (hyperbolically) who cares how fast your prop is turning. <S> Your RPMs are not an outcome. <S> At least, it is not your desired outcome. <S> Your desired outcome is a constant airspeed. <S> Your engine performance is tangential to that. <S> In fact, your RPMs are going to change as your Density Altitude changes even at the same airspeed. <S> Then, throw into the mix a constant speed or otherwise adjustable prop, your Tach becomes almost unusable as a primary for power except when you are changing from one maneuver state to another. <S> Personally, I think that the Control and Performance Method is much better at addressing all of the posters' views. <S> Especially quiet flyer's. <S> In reality, everyone that I fly with uses Control and Performance intuitively. <S> In VMC, Control and Performance is automatic and second nature because you are using sight, sound, and sense of motion primarily to fly the plane. <S> It can still be used when those senses are not available in IMC. <S> Where the Primary and Supporting Method shines is when you start losing the use of your instruments in partial panel flight. <S> It tells and teaches you what instruments (supporting instruments) can be used when the ones you want (primary instruments) are not available or inop.
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Because during certain maneuvers, certain instruments provide more relevant information to a pilot than do others.
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Do turbofan engine cowlings dilate during spool-up? I was watching this Youtube video , portraying a Fokker 70 taking off. I wouldn't have noticed if it weren't for a comment, but during spool up (~ 3:24 in the video), it appears as if the engine cowling is dilating. (See image below, if you don't want to watch the video). According to the person who left the comment, this is due to the pressure changing. I'm having real trouble accepting this — though I do see it with my own eyes, I'm finding it more intuitive to believe something else is going on (I would think something related to the camera, though it seems to be well secured and I can't see any other perspective change). In the end, since intuition is a poor tool for discovering the truth, I decided to ask: Do turbofan engine cowlings really dilate due to spooling up, and is it really because of pressure difference? And is it the whole cowling or only the inlet that dilates? <Q> Now that's an interesting phenomenon! <S> I do not believe that this is a case of an illusion of any sort, or the engine dilating. <S> What the video probably shows, is the engine slightly turning towards the window as takeoff thrust is being applied. <S> Engine mounts are not 100% rigid, this can easily be observed on pretty much any passenger flight if you can see the engine. <S> Any movement of the fuselage and/or wings, and the engines are clearly " bouncing around ". <S> The reason for this is to act as a damper between the engine and the rest of the airframe. <S> In the case of the plane in question, applying T/O thrust imposes a significant force on the engine mounts and the part of the fuselage that the mounts are attached to, resulting in a small inwards turning of the engine nacelles, thus making it appear as if the cowling is expanding. <S> This video shows the exact same phenomenon from a slightly different perspective. <S> At approximately 2:15 mark, as T <S> /O thrust is applied, a red mark on the outer flap mechanism fairing dissapears from view as the engine is shifted a bit. <S> And to further prove my point (having some extra time by chance), here are two images I've created to make this phenomenon more visible: <S> This is a combination of two crops from the video. <S> Exact same location, but different time. <S> The other is just before T <S> /O thurst is applied, the other just before brakes are released. <S> Image is divided into four segments, two of former, two of latter point in time. <S> A vertical and horizontal lines are added for clarity to separate segments "Dilation" is clearly visible: <S> The second image is a combination of the same original images as before, but full frame. <S> They are layered on top of each other, and the one on the top is defined as "difference" layer in Pixlr. <S> This creates an effect that shows areas of the images that differ from each other as bright, while similar areas are dark: As you can see, bright area is visible around engine nacelle. <S> Also horizon line and the runway edge are bright, these brighter lines widen towards the right edge of this composite image. <S> This is because the aircraft tilts from the thrust being applied against the brakes. <A> The answer is unequivocally no. <S> Not only is it not possible, but what would be the point of designing them to do that? <S> The only thing that expands in the turbo jet engine are the turbine blades themselves, but the amount they expand is infinitesimally small. <A> If you line up the two pictures using the tire tracks on the ground and the wing, it is clear the camera position has changed. <S> Look at the outboard hinge for the flaps (with the circular dot) relative to the marks on the ground, for example. <S> Also look at the mark on the ground near the inboard hinge, which is close to the wing in the first picture but half way between the wing and the engine in the second one. <S> In the engine, the fan blade tips will move forward and twist by a measurable amount (a few millimeters and a few degrees) relative to the engine casing, and the blades also increase in length because of the radial forces (that is why the casing has an abradable lining inside, so the blades can cut out their own working position to minimise gas leakage over the blade tips) but the casing itself will not deform by any visible amount. <S> I am dubious about the idea that the engine mounts will "move around" as well. <S> They are designed to be free to expand and contract as the engine casing changes temperature, but that is only a millimeter or two, not something as big as the apparent difference in the two pictures. <A> I don't see any dilation or change to cowling size except I could "see" dilation is in the bottom left of the window. <S> The edge of the engine anti-ice and a line in the window changed distance. <S> See my red rectangles in the attached photo. <S> I believe this is an optical illusion. <S> I suspect the cabin pressure increased as the engine spooled up and provided more bleed air. <S> This pushed against the window and slightly distorted it. <S> That distortion changed the distance of those lines. <S> Additional the entire engine cowling could flex a bit as the thrust would cause torque on the pylon. <S> This could also explain the change in distance of my reference points (as pictured). <A> As the aircraft starts its takeoff roll, you can see the window frame flex in and out. <S> Rather than the engine distorting or seeming to turn in, it is the side of the fuselage flexing. <A> In fact at 1:04 you have the same effect during pushback with engine off yet.
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One possibility is that as the engine spools up, it's creating a low pressure region around the entire front cowling, causing the fuselage to bulge out slightly. I think it's a camera distortion caused by vibrations: an effect you can see when some harmonics are prox to shutter frequency and can cause image distortion.
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What should I do if I lose situational awareness while in the pattern? Let's say that I'm doing some pattern work in my favorite little Cessna or Diamond at my favorite little non-towered airport. Everything is going just fine, I'm on the downwind leg... Or, wait a minute, am I on the crosswind leg? Which runway are we using today? I just heard another plane on the radio that I can't see; what did she say, again? Is she behind me or are we on a collision course? In short, I suddenly realize that I don't have a full picture of what's going on here. What are my options here, and how should I choose between them? Here are my ideas, from best-sounding to worst-sounding: Just climb out of the pattern, then fly a safe distance away from the airport, descend, and fly back into the pattern. I assume that after starting the climb, a quick radio call wouldn't hurt: "Wobegon traffic, Skyhawk eight three four sierra tango, climbing out of the pattern and going west." (I've always heard that you should never descend or climb directly into the pattern, but I've never heard that you shouldn't climb out of the pattern.) Keep flying, keep looking out the window, and talk fast on the radio: "Aircraft at Wobegon, where are you again? I'm not sure exactly where I am, do you have me in sight?" (I'd feel stupid saying this, but it's better to speak up and feel stupid than to stay quiet and be stupid.) Keep flying, keep looking out the window, stay quiet, and just try to figure out what's going on. <Q> It is the advice of the FAA that you should be looking out the window quite a bit when VFR in the pattern. <S> According to this AC related to traffic patterns : Collision Avoidance. <S> The pilot in command’s (PIC) <S> primary responsibility is to see and avoid other aircraft and to help them see and avoid his or her aircraft. <S> Keep lights and strobes on. <S> The use of any traffic pattern procedure does not alter the responsibility of each pilot to see and avoid other aircraft. <S> Pilots are encouraged to participate in “Operation Lights On,” a voluntary pilot safety program described in the AIM, paragraph 4-3-23, that is designed to improve the “see-and-avoid” capabilities. <S> If you are worried you should (over) self announce, if you lose track of an aircraft you should do every thing in your power to make sure that the other aircraft know where you are in the pattern. <S> Self-Announce Position and/or Intentions. <S> “Self-announce” is a procedure whereby pilots broadcast their aircraft call sign, position, altitude, and intended flight activity or ground operation on the designated CTAF. <S> This procedure is used almost exclusively at airports that do not have an operative control tower or an FSS on the airport. <S> The FAA also offers lots of advice on how to fly a pattern here. <A> By empty sky, I mean if you think somebody might be nearby and you aren't sure where they are and don't have them in sight, identify a patch of sky where they're not , and head for that. <S> Don't climb or descend while doing this. <S> Most midairs are from aircraft on similar tracks that converge while one is descending or climbing, within a few miles from the airport. <S> The key is, you have various blind spots and you shouldn't head into the blind spots. <S> Head for sky you can see. <S> Yes announce your position and intentions, without cluttering up the channel with chatter. <S> With practice and familiarity, your ability to think about multiple tasks will improve and your situational awareness will improve with it as you gain the ability to think outside the aircraft once your physical actions start to become automatic. <A> Aviate, navigate, communicate. <S> Tell yourself to keep calm. <S> Look around you: If your current heading is not taking you over the runway or towards visible traffic, keep your heading and altitude. <S> Look around you: is there any feature outside that you recognize? <S> Chimney, church, lake, forrest? <S> If yes, and the course there does not cross the runway or other traffic, make a standard rate turn towards the feature. <S> After you gain some distance from the field, and get yourself oriented again, approach the field according to local procedures. <S> Keep calm :) <A> Your DI will tell you your heading and you can work out which leg you are on from that. <S> If the runway in use is 09 and you're flying 270 <S> then you're downwind. <S> If the pattern is left hand and you are flying 180 you're on base, if it is 360 you're crosswind. <S> Obviously, heading is not track. <S> It gets harder if your runway is 23 <S> and there's a 20kt wind from 170 to allow for. <S> But you could get a vague idea of where you are IF you've flown the circuit correctly before you lose situational awareness. <S> I think, in the pattern, you are more likely to lose awareness of where you are in relation to other traffic, <S> stop paying attention to your height or (let,s face it <S> , we've all done it ) fly the wrong way round the circuit, rather than forget what leg you're flying
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If you are confused somehow about your situation over an airport, and there are other aircraft around, head for empty sky away from the airport beyond the pattern/circuit and get reoriented. Don't expect too much at your level. Announce your intentions, don't worry about specific phraseology, for example: " NXYZ is leaving ABCfield traffic pattern with heading 123 at 1234 feet " will do. Keep aviating, navigating and communicating.
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Has anyone burned hydrogen in a turbine? I am just wondering if supplying compressed hydrogen to a turbine would be a better fuel as it has three times the octane rating of kerosene. It just seems better all around. <Q> Yes, indeed the plan to build a hydrogen-powered jet laid the groundwork for using hydrogen in the Centaur rockets and the upper stages of the Saturn 5 . <S> While hydrogen was used only experimentally in test rigs , the Soviet Union built a derivative of a regular airliner, the Tupolev 155 , for testing hydrogen and natural gas in flight. <S> EDIT: <S> NACA also did in-flight testing. <S> Please see @jayhendren's answer for details. <S> So yes, the Tu-155 was indeed flown on several occasions with one hydrogen-powered turbofan. <S> While the left and center engine remained NK-8 s, the right engine was replaced by a NK-88 <S> which was adapted for LNG and hydrogen. <S> Other projects like one for a hydrogen-powered supersonic airliner <S> sadly ended with the Soviet Union itself. <S> Tu-155 <S> Cutaway view (picture source ) <S> Hydrogen is also the prime propellant in hypersonic ramjets , but those are not turbines. <S> Hydrogen has a wide mixing ratio with air where it will burn. <S> Also, being gaseous, it mixes much more quickly with air, so the combustion chamber can be small. <S> When a converted J-57 was experimentally run on hydrogen in 1957, <S> The test engineers were agreeably surprised by the ease of engine operation. <S> They ran it at full power and throttled back so far that the air fan was revolving so slowly the individual blades could be counted. <S> Under this latter condition, the throttle could be opened and the engine would quickly and smoothly accelerate to full power. <S> They found that the temperature distribution was good and there were no major problems. <S> But Niels is correct - its low density makes hydrogen problematic. <S> As Alexis W. Lemmon, Jr., reported in May 1945 in his report on possible jet fuels (from history.nasa.gov ): <S> " <S> Although the liquid hydrogen-liquid oxygen system has by far the highest specific impulse performance of any system considered in this report, the low average density of the fuel components almost completely eliminates this system from all but very minor applications." <A> For fuels intended for use in aircraft, the key performance parameter is the energy density of the fuel: how much potential work is stored in how many liters of stuff. <S> High energy density means the fuel tanks will be small and the energy released upon burning a liter of it will be large. <S> The problem with using hydrogen as aircraft fuel is that its energy density is way lower than that of kerosene or diesel (because a liter of hydrogen at atmospheric pressure contains far less chemical potential energy than does a liter of kerosene), and squeezing it down to reduce its volume requires cryogenic refrigeration which hugely increases cost and weight, and the octane rating advantage of H2 is not balanced by these disadvantages. <S> Specifically regarding burning hydrogen in brayton cycle turbines, this is possible but economically impractical because the cost to make a liter of hydrogen is far greater than the cost to refine a liter of jet kerosene from crude oil. <A> Von Ohain's first prototype of his HeS 3 turbojet, the HeS 1, burned hydrogen in the first runs. <S> Only after some modifications was he able to make it work with a liquid fuel. <S> https://en.wikipedia.org/wiki/Heinkel_HeS_1 <A> This is not fully on topic ('Aviation'), but answers the question in some way: Hydrogen is currently considered the 'fuel of the future' for existing and new gas turbines in power plants, for small and large gas turbines equally. <S> The industry is working to enable all existing turbine lines to handle that, and the modifications are minor (well, minor compared to the complexity of a modern gas turbine). <S> Many models are already successfully enabled and proven, and the market is expecting to get the first requests soon. <S> Overall, it is quite easy to use hydrogen - just maybe not on an airplane. <S> The main reason to go for hydrogen burning is that it enables hydrogen storage as a battery - when there is extra power available (preferably solar or wind), it gets converted to hydrogen, and when the power is needed, it gets burned in existing gas turbines. <S> This would allow to save trillions of existing investments in power plants by converting them into zero-emission hydrogen-burning plants. <S> [Disclaimer: I have a professional relationship to such a company; however, this is not restricted information] <A> There is an extensive history of NACA's and NASA's experimentation with hydrogen as a fuel on the NASA history website . <S> In the 1950s NACA burned hydrogen in a turbojet engine on a modified B-57 aircraft as part of Project Bee: <S> A technical report on the in-flight performance of the hydrogen-powered turbine was published and is available for download on the NASA website . <S> The experiments with hydrogen as a fuel source for turbine engines were successful enough that the Lockheed CL-400 high-altitude reconnaissance aircraft was designed to use hydrogen fuel: <S> Ultimately, however, the CL-400 was cancelled, although some of the research for this project made its way into the now-famous SR-71.
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NACA (the predecessor to NASA), has burned hydrogen in a turbojet engine in flight.
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Aerodynamics of Flight Control Surfaces From what it appears to me, flight control surfaces seem to be taken for granted. In terms of how they actually work and what kind of physical outputs they give in terms of forces and such. Take for example the elevators of a Boeing 777, if the pilot wanted to pitch up, the elevators would move up. What are the physics behind this? Is it air being deflected thus a change in momentum occurring to pivot the aircraft's tail down or is the angle of attack changing due to the moving nature of the trailing edge? or both? I am quite interested to know because I want to simulate Aerodynamical forces in a game I plan to make soon. Diagrams would also be useful but not required. Thanks in advance. <Q> Thankfully, aerodynamics in the usual flight range is linear. <S> Therefore, there is a gradient of lift over angle of attack and another one over the flap deflection angle. <S> Both are constant over a range of maybe ±15° and can be combined. <S> The angle of attack is referenced to the fixed part of the flight surface and the deflection angle to the moving part relative to the fixed part. <S> Another parameter which influences lift is the camber of the flight surface. <S> Positive camber produces more lift at the same angle of attack. <S> Deflecting a flap changes this camber, and its effect can be linearly added to that of the angle of attack. <S> Is it air being deflected thus a change in momentum occurring to pivot the aircraft's tail down? <S> Yes, when a flap moves, the angle of attack stays constant but the camber of the flight surface changes, thus producing a change in lift. <S> And yes, lift is produced by deflecting a stream of air. <S> Things get more complicated and interesting when the aircraft leaves the angle of attack range in which aerodynamics is linear. <A> A trailing-edge control surface, when it deflects, changes the camber of the overall airfoil. <S> More camber means more lift, in whatever direction that airfoil is mounted. <S> In your example, adding up elevator increases the horizontal stabilizer's camber, which increases the downward force it applies. <S> Philosophically, "why" it does this is just, well <S> , that's how air behaves when you push it past something with that shape. <A> Well, both. <S> Lift can be described as a moving wing colliding with air molecules at an angle, the result of the collision is the wing moves one way and the air mass the other, as per momentum physics. <S> Moving the trailing edge, or the entire surface, increases the angle of attack, resulting in more lift at a given speed $V$ : $Lift$ = <S> 1/2 × Lift Coefficient x Air Density x $V^2$ x Wing Area Deflection of the control surface produces a linear response to lift, as Peter Kampf says. <S> A graph of angle of attack vs lift coefficient generally shows a linear relationship through most of the unstalled AOA range. <S> Further inspection of the effect on AOA, of deflecting a trailing edge flap down, as compared with "drooping" a leading edge, does indeed show doing this changes the angle of attack of the lifting surface! <S> Flaps are usually near the wing roots, and leading edge slats near the wing tips, for this reason. <S> We want the root to stall first. <S> Yes, deflecting a control surface changes the camber of the wing, which also factors into the lift coefficient, but, relative to the original AOA of the wing/fuselage <S> , the flapped portion of the wing will stall at a lower AOA than the slatted portion. <S> Therefor, deflecting the control surface also changes AOA. <S> The importance of this concept is highlighted in a slow flight coordinated turn. <S> Use of ailerons without coordinating rudder may result in a sharp roll in the opposite direction of the intended roll, because the AOA of the "down" aileron wing now exceeds its stall AOA. <A> From an old uni book on stability & control of aeroplanes, showing the pressure distribution over the horizontal tail: <S> First picture: no elevator or trim tab deflection, pressure peaks at the stabiliser nose at two different Angles of Attack $\alpha_h$ . <S> Two different elevator deflections $\delta_e$ : <S> pressure peaks at the elevator profile nose. <S> Two different trim tab deflections $\delta_{te}$ : <S> pressure peaks at the trim tab nose. <S> The magnitude of the pressure peaks per degree deflection is a function of the surface area. <S> Location of the peaks is a function of which surface has AoA ≄ 0.
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In your example, a trailing-edge up deflection decreases camber, the surface produces less or negative lift which produces a moment around the center of gravity.
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What are the limits of ground effect over water on an airliner plane at cruising speeds? What height over a fixed plain (such as water) can a plane begin to take advantage of the ground effect or when air is compressed between the wing and ground near cruizing speed? Could an airliner type plane fly above the water for an added lift for range in an emergency where a plane may lack the power to climb? <Q> Ground effect only comes into play within about 1 wingspan’s <S> height above a surface <S> and it is largely unnoticeable until approx 1/4 to 1/10 of a wingspan above the surface. <S> While it is true that ground effect greatly increases the lift to drag ratio of the wings, it does not reduce parasite drag nor does it account for the fact that it is more efficient to fly at higher altitudes where the atmosphere is much thinner for greater speeds per unit of fuel consumed. <S> Flying low to the ground is dangerous as there is less margin for error if something goes wrong and would limits operations to day VFR conditions. <S> Transport airplanes have been test flown and certain flight profiles have already been determined to offer the greatest range. <S> These occur at altitude and on reduced power settings. <S> Heavy sea transports which to use wing in ground effect for lift have been proposed in the past, but been found to be in efficient compared to existing jetliner designs. <S> WIG craft have been used for short transport missions like island hopping, where that kind of a craft would be faster than a ship, and more efficient than a light airplane. <A> What height over a fixed plain can a plane begin to take advantage of the ground effect or when air is compressed between the wing and ground? <S> It varies, but, generally speaking, ground effect usually becomes noticeable somewhere around half the plane's wingspan above the ground. <S> So, for a plane with a 50-foot wingspan, ground effect would only be viable below 25 feet. <S> Could an airliner type plane fly above the water for an added lift for range in an emergency? <S> Theoretically, yes, but it's unlikely to be very helpful. <S> Flying that low is dangerous in and of itself. <S> Even out over the water, there are boats, buoys, rogue waves, breaching whales, etc. <S> , etc., etc. <S> Not to mention, you have to be very careful when you turn not to dip your wing in the water, and even a slight downdraft will kill you before you have a chance to react. <S> Fly high enough, and the reduced air density (and subsequent reduced drag) can increase your range more than what ground effect would give you. <S> Ground effect is highest over a smooth surface, so if there are waves, you won't get as much drag reduction as you might be expecting. <S> That all said, it is possible, and has been done several times. <A> Flying in ground effect for either economy (reducing power needed to fly) or in an emergency (engine out prevented climbing, but allowed ground effect flight for considerable range) has been done many times, and there have been vehicles designed to fly almost entirely in ground effect (ekranoplan was the Russian name for these).
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As noted in the answer linked in comments , the practical limit for ground effect is about half the wingspan over a relatively flat, impermeable surface (you'll get better effect from smooth water than from heavy swell, for instance).
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How do pilots avoid clouds under night VFR? When flying under visual flight rules (VFR), pilots have to be able to see far enough away to be able to avoid running into other aircraft or the ground. Therefore, VFR flight requires good visibility with a high (or no) cloud ceiling; this is known as visual meteorological conditions (VMC). It also requires that pilots avoid clouds like the plague, since clouds (on Earth, at least) tend to be on the opaque side, and a cloud that you can't see through could potentially be hiding something that it would be very bad to run into (such as someone else's aircraft). Avoiding clouds is easy enough during the daytime, if the weather is good (the big white things tend to be fairly visible as long as you aren't actually inside one), but, in many countries (including such biggies as the US, France, and Australia), VFR flight is also permitted at night. As clouds are not usually polite enough to illuminate themselves for the benefit of nearby pilots, they tend to blend in rather well with the dark sky (except sometimes when bright moonlight is present), the only hint of their presence being that they occlude background stars (which provides absolutely no information about whether those stars are being hidden by a small cloud close by, or by a big cloud further away, and depends on the stars being easily visible to begin with [which is not always the case, even at night]). So how do pilots avoid clouds when flying VFR at night? <Q> I will caveat my answer by saying that most of my night flying has been under IFR, but because of that I have lots of experience going in and out of clouds at night. <S> It starts with a good weather brief, and don’t forget to ask for PIREPS that might cover areas further away from the field. <S> True enough the bases can be ragged, and little puffies can lurk in unexpected places, but if you know where the layers are called you are well on your way to avoiding being at the same altitude. <S> To add to one of the comments, moonlight is helpful, but so is ground lighting. <S> For example, if your eyes can trace a lighted road off in the distance, but at approximately 20 degrees below the horizon the car lights become blurry, then disappear, it is probably because of a cloud between you! <S> Angle away, or descend below the deck until the horizontal visibility range increases. <S> If you start skimming clouds you will know it immediately because your anti-collision light will blossom and reflect red all over the inside of the cockpit. <S> If you still have ground lights in sight <S> and you know the clouds are stratified, I would start a gentle descent. <S> If there are a lot of vertical buildups and you pop into one and lose sight of the ground, make a level 180 and get out of there. <S> Most non-instrument rated pilots are taught to deal with inadvertent IMC in this way. <S> As I mentioned in my answer to your other question, make sound risk decisions. <S> If you are uncomfortable with the weather conditions or your ability to remain clear of clouds, then choose to not fly VFR at night. <S> But once you get a few night flights under your belt <S> I think you will find that they can be very enjoyable when conditions are good. <S> It opens up a whole new perspective on things! <A> One thing you can do to minimize the risk of cloud encounters at night, besides the obvious one of staying below reported or forecast cloud layer altitudes, is to maintain a positive dew point spread in the air mass you are flying in, to the extent you can, since cloud usually won't form until the spread becomes zero. <S> So if the dew point is 8C and it's 20C on the surface, a 12 degree spread, I would avoid climbing any higher than an altitude that gives a 2 deg C spread, about 5000 ft AGL, which should give a 1000 ft margin below any cloud that may form. <S> Of course, if you end up flying into more humid air with a higher dew point, you're back to square one, so you need to take into account factors like potential changes in humidity (flying from over dry land to over a large lake for example). <S> Beyond that, it's a case of being good at making 180 degree turns in IMC when the ground disappears. <S> In night VFR, if you encounter a cloud the priority is to return to the clear air you were in just before, so you simply make a level 180 degree turn on the gauges and wait to break out, then descend (you want to avoid climbing/descending turns in IMC when you only have a couple hours of time under the hood). <A> Starlight, moonlight and light pollution from the ground are often adequate to see where the clouds are almost as well as you can during the day. <S> But not always - if there's a high overcast to block the stars and a new moon and you're out in the back country or over the ocean, it might as well be IMC. <S> Pilots have to use their judgement and not fly VFR at night even in VMC if conditions are such that they can't be reasonably assured of maintaining VMC.
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At night distant clouds can be difficult to see, but you can use ground lighting to gauge where the coverage is.
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How was the endurance test in the Cessna 172 legal? The flight in the Cessna 172 lasted around 64 days with two pilots switching to fly the plane. To my knowledge both FAA and EASA have rest periods which pilots have to follow. Also the refueling was done by a truck matching the speed and handing over a hose to refuel. How was this flight legal regarding rest periods and refueling maneuver? <Q> This flight would have been operated as a private flight under 14 CFR 91 under today's regulations. <S> The flight, duty, and rest requirements are specified only for certain commercial operations including airline, charter, and fractional. <S> Flight instruction is also generally limited to 8 hrs in a 24 hr period. <S> Paid pilots routinely fly 12-14+ hours in a day, including in certain patrol activities and in flying private jets. <S> Refueling is not generally restricted by FAA aiation regulations in a way that would specifically impact this operation. <S> As with the flight time concern, the catch all "careless and reckless" regulation might apply first. <S> For some of the same reasons that the crew flight time was not restricted, many of the maintenance requirements such as 100 hr inspections, would not be required of a private flight. <S> However, the 100 hr seat rail inspection AD would be problematic today. <A> The flight you're referring to occurred in 1959 . <S> The Federal Aviation Agency , a precursor to the Federal Aviation Administration, had just been newly established in 1958, and hadn't drafted the rules you're referring to yet. <A> As noted in the comments <S> Crew Rest Periods are only applicable to commercial flights operating under part 121, 135 and 91K as per the FAA's regulation, specifically 14 CFR § 121.471 . <S> But it does not apply for flights strictly operating under part 91 which they likely were. <S> You can make a case that they could have potentially been in violation of 14 CFR § 91.13 - Careless or reckless operation. <S> (a) <S> Aircraft operations for the purpose of air navigation. <S> No person may operate an aircraft in a careless or reckless manner so as to endanger the life or property of another. <S> but that is the FAA's catch all and somewhat broadly applicable when they see fit. <S> There have been various endurance records set over the years ( <S> all legally) and in all cases precautions were taken to ensure that the flight was safe. <S> Generally this involves two pilots taking shifts however the recent Solar Impulse flight set the solo record. <S> As for the refueling, there is no regulation that an aircraft must be on the ground, or stopped in order to re-fuel, the military refuels mid air quite often .
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Regarding flight time, duty periods, or rest requirements, no current regulations would have specifically imposed limitations on this flight.
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Are there any single-pilot aircraft certified in the Part 23 Commuter category? Is it possible to certify an aircraft under FAR 23 Commuter Category with single pilot ops only? Like, there is just one seat in the cockpit and up to 19 passengers.Does anyone know of such an aircraft flying? <Q> It looks like it's possible but not common. <S> There's an STC for the Twin Otter that authorizes single-pilot operations in the commuter category if various upgrades have been made. <S> At least, that's my reading of it: <S> The Airplane Flight Manual Supplement (AFMS) lists equipment that must be installed and operative to operate the aircraft single pilot. <S> And: <S> FAA STC SA02682LA incorporates upgraded engines, upgraded propellers, increased maximum takeoff weights (MTOW), structural and aerodynamic modifications, and the aircraft category and design characteristics were updated to Title 14 of the Code of Federal Regulations (14 CFR) part 23 commuter category. <A> HondaJet is certified for single-pilot operation for Part 23. <S> Note that 14 CFR Part 23 Amendment 64 and later removed Utility, Acrobatic, and Commuter Categories and now refer to all of them as Normal Category. <A> <A> Florida Flight Center says CE-501SP and the CE-551SP are FAR part 23 certified aircraft. <S> Both of these airplanes may be flown single pilot without a waiver as long as your checkride was completed in one of these aircraft to single pilot standards.
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The Phenom 300 is certified under Part 23 and you can be typed as single pilot in it. The Twin Otter DHC-6-300HG™ type rating designation is DHC-6HG and may be operated with or without a second in command (SIC) with certain limitations.
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Why does a turbine helicopter need to spin a tail rotor? Should not the exhaust of the turbine supply enough byproduct to deflect and maintain yaw with a simple deflector (i.e. rudder/stabs)? <Q> Well, that’s complex. <S> Where should I begin? <S> The main job of the tail rotor is to use its long lever arm and directed force/thrust (horizontal lift) to counteract the torque of the spinning main rotor. <S> See the previous topic: <S> Does a turboshaft's exhaust provide any thrust? . <S> Energy is finite. <S> In simplest terms, any energy taken out of the engine before the exhaust gasses reach the exhaust nozzle will be energy taken out of the thrust generated. <S> Turbofans generate less thrust with their hot-side core exhaust than Turbojets. <S> Turboprops generate a lot less thrust with their exhaust than Turbofans. <S> And, Turboshafts generate less thrust than that. <S> The most important contribution the exhaust has in a Turboshaft is to dispel heat and waste from combustion. <S> NOTAR (No Tail Rotor) <S> helicopters already exist that use Coandă Slots and ducted thrust instead of a tail rotor. <S> An internal fan is used instead of the exhaust, though. <S> The anti-torque thrust a helicopter creates must be variable with the ability to fine tune. <S> If the engine fails, you still need yaw control until you land. <S> As complex, damage-prone, maintenance-dependent, and expensive <S> the typical tail rotor system is, if it were possible to use your idea with today’s engine technology, it would have already been done. <S> I am sure there are other reasons. <S> But, great question. <S> Way to think out of the box. <A> The turbine output is very hot and therefore needs to be shielded in some way if it is to be routed through any part of the helicopter. <S> This shielding adds cost and weight, so it's generally avoided. <S> The turbine itself is situated very near the center of gravity of the helicopter, so the turbine output has very little leverage on the helicopter's rotation in its current location. <S> To use the turbine output, it needs more leverage, so it would need to be routed to the end of the tail to a similar location as the tail rotor (which is why the tail rotor is located where it is - to add leverage). <S> Doing this would mean creating a thermally shielded duct down the inside tail... which would add cost + weight. <S> You also have the problem that you need to control the thrust from the tail to make the helicopter rotate left and right. <S> That's not easy if you are using the output from the turbine because that's pretty much fixed unless the helicopter is ascending or descending. <S> There is a version of helicopter that uses blown air rather than a tail rotor - see the <S> https://en.wikipedia.org/wiki/NOTAR . <S> This still has the turbine output in the usual place, but uses a fan build into the tail to blow air sideways rather than have an external a tail rotor. <S> This makes the helicopter much quieter in operation and reduces the risk of injury to persons working around the helicopter whilst it is on the ground with the engine running because there is no tail rotor spinning for them to get injured by. <A> The turbine engine of a helicopter has very little exhaust thrust. <S> They are turboshafts , designed to extract every bit of useful energy for driving the main rotor shaft. <S> From Wikipedia: A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. <S> In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust and convert it into output shaft power. <S> A helicopter tail needs to apply between 10 and 20% of the main rotor thrust in order to compensate for the torque of the main rotor. <S> Re-designing the turbine engine to leave enough hot exhaust thrust for the tail is always less efficient than re-directing the extracted main shaft thrust, for instance with a fan driven by a gearbox. <S> The NOTAR engine uses such a fan, but not to provide all of the required tail thrust - the downwash of the main rotor is deflected sideways, creating a large part of the required anti-torque thrust.
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The exhaust gas of a Turboshaft engine does not produce a large amount of thrust for the very large amount of torque the rotor-powertrain combination produces.
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Why do helicopters have skids? Why can't they just land on the helicopter's floor? If it's for stability, they could still use skids which are shorter than what is commonly used. <Q> Image source Larger helicopters have landing wheels, and as we can see on the picture above, they are placed as far outward as practically possible in order to provide stability in the landing. <S> Touch down one wheel on an sideways inclined slope, lower the collective, and the helicopter will align itself onto the slope with: <S> The location of the Centre of Gravity (CoG) always in between the wheels. <S> The higher the CoG, <S> the wider the landing gear impact points must be. <S> The weight being supported on clearly defined and structurally reinforced points. <S> Even if the bottom of the helicopter is perfectly flat, the landing ground may not be, and to support all of the weight at any random point at the bottom requires a lot of relatively useless weight for the re-inforcement. <S> The behaviour after first wheel touchdown being clearly defined. <S> The wheel is a point of impact upon the landing plane, mathematically much more defined than a plane of impact upon a landing plane if the latter is curved. <S> All the above is for wheels, which allow the helicopter to taxi on-ground. <S> Skids perform all of the above functions apart from the on-ground taxiing, and are cheaper and lighter than retractable landing wheels. <S> Of course, the other downside is that they have more drag. <S> One would not want to land this helicopter without the skids! <A> Physically they likely could, but helicopters (and all aircraft for that matter) tend to have stuff mounted to the bottom like antennas, probes, cameras etc. <S> so adding some kind of landing gear or skid helps to provide clearance for all that. <S> This question covers a bit about whats mounted where. <S> The belly of a helicopter also tends to not be perfectly flat (depending on the model) so belly landing can lead to some roll which may allow the rotors to scrape the ground. <A> Skids are especially beneficial when the helicopter is supposed to land on rough ground, e.g. grass. <S> They move the body and the rotors farther away from the ground, thus giving both more clearance. <S> Compared to extending the body to the ground to achive the same effect, skids add less weight and significantly less air resistance. <S> Compared to wheels they are better suited for rough ground, as they have a larger contact area and thus tend to sink less into the ground. <S> Wheels on the other hand have the advantage when the helicopter usually lands on concrete or other solid ground. <S> Here they allow taxiing. <S> That's why you tend to see skids on smaller helicopters which tend to land on grass or other uneven terrain, while larger helicopters, which tend to land on more solid ground, tend to have wheels. <S> Also, skids are simpler than wheels, which also suits smaller, cheaper helicopters better. <A> Skids, as opposed to wheels, allows the pilot to get some sense of balancing tail rotor counter torque before lift off. <S> Skids would provide more drag until the pilot "got it". <S> Same thing moving forward, backwards, or side to side. <S> The skid friction limits movement (or damps it if you will), rather than creating a nightmare of correct/overcorrect in 2 dimensions. <S> Skids also add an important amount of rotor clearance, and offer simplicity, reliability, and light weight. <A> An additional benefit of longer skids is some energy absorption upon a vertical crash. <S> The skids are generally designed to bend outwards and up during impact. <S> This can be seen occurring on many helicopter crash videos. <S> The design of impact absorbing skids is covered extensively here . <A> As pointed out above, not all helicopters use skid style landing gear. <S> Some have either a fixed or retractable wheeled undercarriage. <S> These offer excellent mobility on paved or short cut grass airfields, surface taxiing, rolling takeoffs or landings or for movement aboard ship. <S> Surface taxi also consumes a little less fuel than hover taxi or takeoff from an IGE hover, but are more complicated, heavier, and expensive than skid type landing gear. <S> Smaller, utility helicopters usually use a skid type landing gear For several reasons. <S> Lightweight. <S> Inexpensive. <S> Flexible and can absorb impact of a hard landing or crumple to absorb energy. <S> Provides a large, stable support for pinnacle or slope landings. <S> More even distribution of aircraft load for landings in soft or waterlogged fields. <S> Lends itself better to being fitted with fixed or emergency inflatable floats for over water operations. <S> Can provide support for personnel flying outside the airframe. <S> The downsides to skids are <S> Do not allow the helicopter to be easily moved or towed on the ground; must be fitted with towing dollies or placed on towing trailer. <S> Surface movement limited to hover or air taxi. <S> Are fixed and cannot be retracted and faired, thus adding more drag in flight. <S> Easier to snag on obstacles and wires during surface operations. <S> More susceptible to side loads during takeoff and landing, which can cause dynamic rollovers. <S> Great skill must be used during rolling takeoffs, shallow descent landings or autorotation to keep the aircraft moving in a straight line down the runway to prevent side loads. <S> The aircraft’s fuselage is shaped primarily to provide the best aerodynamic fairing for the cabin, engine and transmission and aircraft systems; it is not necessarily the most stable platform and does not provide any shock absorption in case of a hard landing or an autorotation landing. <S> Landing gear is designed to solve that problem.
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The siding of the skids is based on a lot of things from the ability to provide solid, stable support on uneven terrain to prevent the onset of potentially deadly ground resonance during a harder than normal landing to offering good ground clearance. Easy to replace if damaged.
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Are helicopter pilots required to use GPS navigation? Some helicopter crashes are caused by a disoriented pilot. This would presumably be impossible with a GPS with terrain maps. Are pilots required to use a GPS when flying a helicopter in the US? <Q> There are some approaches to landing that require GPS (called RNAV) approaches, but the airports that they serve usually have other types of non-precision approaches as well. <S> Helicopters have specialized maps that are called Helicopter Route Charts that are supposed to provide additional information relevant to helicopter pilots. <S> These charts may be carried in paper form, although newer aircraft also have them as electronic moving maps. <S> The pilots may also (but are not required to) be using electronic flight bags with moving maps/terrain/synthetic vision. <A> A disoriented pilot may include pilots who are disoriented with respect to attitude. <S> GPS does not provide attitude information, although it could be inferred to a degree. <S> A Ground Proximity Warning System (GPWS) uses GPS data and digital elevation models (terrain) to predict terrain collisions. <S> Such a device gives warning when an aircraft trajectory is likely to collide or nearly collide with terrain. <S> These systems are common on fixed wing and rotorcraft. <S> In 2002 <S> the US FAA mandated TAWS or GPWS for all turbine airplanes having 6 or more passengers. <S> I am unaware of a similar requirement for helicopters, but I seldom fly helicopters, particularly larger than a 206. <S> For helicopter flights there is only a requirement in the US to have maps or charts suitable for the navigation used. <S> If VFR these could be Helicopter charts, terminal charts, sectionals, WAC/ONC, even instrument charts. <S> Old man Jeppesen just made notes on a notebook, and later marketed them. <S> To specifically answer your question, there are no generalized requirements for GPS or moving map GPS in helicopters. <S> And as a relevant footnote, GPWS systems have been available at a relatively low cost for general aviation aircraft for well over 20 years, which would provide terrain warning, with verbal audio in the pilot cabin. <A> GPS is never required in any aircraft. <S> No navigational aid/equipment is required in aircraft flying VFR (Visual Flight Rules) or Daytime Special-VFR except for a magnetic compass. <S> Nighttime Special-VFR and all IFR (Instrument Flight Rules) require navigational equipment specific for the flight undertaken and/or the Instrument Procedure flown. <S> This may or may not mean <S> GPS, VOR, DME, LOC, and/or ADF may be required. <S> Even the magnetic compass is not considered a navaid in an aircraft. <S> It is technically a flight instrument.
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No, pilots are not required to use GPS maps or moving GPS while flying helicopters or fixed-wing aircraft. It depends on the circumstances.
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Can PC joystick simulate aerodynamic lock in spin? I never explored joysticks for playing simulators on PC. Can some kind of joystick simulate aerodynamic lock during spin? You do hands off control stick and it stays there, won’t center as usual. I understand that force feedback is often included in such products, but can force feedback override auto centering? <Q> The stick feels pretty light in that situation and kind of remains where you put it, almost like a helicopter cyclic stick with the trim button released. <S> When switched on, the force feedback can act like a passive spring and accepts some input parameters for varying the feel. <S> The neutral position can be varied, the return position of the spring. <S> All pretty course, not bad for the money, although the stepper motor produces grainy feedback forces. <A> I think it's more of a question about the simulator software than the joystick. <S> I do not know the current status of "consumer grade" sim software, but I'm highly doubtful that they would be able to mimick actual feel of stick forces in a very natural way. <S> Doing it would require quite a lot of computation. <S> FS2004 did emulate the affect of speed on control forces, but it was pretty crude. <A> They exist, but few of them, if any (in the consumer market) produce satisfactory results. <S> Good force feedback simply cannot be done cheaply, and this restricts the market to niche enthusiasts and professionals. <S> It is relatively easy to produce 'effects' such as vibration and impulses, and most consumer FFBs can do it. <S> But to simulate the whole range of forces reqire a specialised drive and very solid construction. <S> In addition (and perhaps because of the small niche market of such devices), none of the common game simulators even attempt to simulate control forces reasonably. <S> Tellingly, even the Windows interface (API) to drive FFB hasn't been updated for some 15-20 years (it even retarded a bit). <S> But all is not that bad. <S> While I'm still not aware of any FFB stick/joystick controller that can do a satisfactory job, there are at least FFB yokes (such as this one ) that can potentially deliver a relevant experience in GA aviation. <S> They are not cheap by gaming standards ($1500+), but very cheap by aviation standards. <S> To overcome software limitations, they typically extract flight data from the games and run their own force simulation, which requires some fiddling with set-up. <S> The car racing game industry is in a better position: the number of enthusiasts is larger, and an FFB steering wheel is a simpler device (being a single degree of freedom and lower force). <S> There are quite a few racing FFB steering wheels on the market that can be considered decent, but even they are fairly expensive (~$1000).
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For example Flight Simulator 2004 did have force feedback modeled into it, but I don't recall it being very sophisticated. Yes there are PC joysticks that can remain in an off center position: the active feedback joysticks, without the force feedback switched on. Such effects can only be produced by so called 'force feedback' (FFB) devices.
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What is the purpose of using 8.33 kHz instead of 25 kHz frequency spacing? What is the purpose of using 8.33 kHz instead of 25 kHz frequency spacing? <Q> The purpose is to accomondate more dedicated frequencies within the airband VHF range (117.975 to 137 MHz). <S> Increasing number of stations made this necessary, if the smaller division was not implemented, it was estimated that only 70% of future requirements for frequencies in Europe can be met. <S> 833radio.com has further information and an nice table describing the channel spacing: <S> For simplicity, the actual 8.33 channels are displayed as rounded to .005 values. <S> For example to use the frequency 118.0083MHz, you dial 118.010 <A> Ex1. <S> There are 41 channels in the frequency space of 118.0 and 119.0 MHz, inclusively, with 25 kHz spacing. <S> Ex2. <S> There are 121 channels in the frequency space of 118.0 and 119.0 MHz, inclusively, with 8.33 kHz spacing. <S> Since current airband transceivers are analog instead of digital, we needed some way for accommodating the increased amount of use on the airbands. <S> We use analog receivers to this day because of their nature of transmitting and receiving as much as possible regardless of the situation or environment. <S> The transmission may be faint, staticky or garbled, but it can still be received. <S> On the other hand digital transceivers like cell phones can use much fewer frequencies to accommodate many times the amount of information and users by compressing the information. <S> A digital transmission is usually much clearer and more distinct with less distortion even over great distances with lower power. <S> But, digital transmissions are an all or nothing proposition. <S> Any loss or interruption in the flow of the data may render that portion of the information unreceivable. <S> One word in a transmission may be entirely lost, changing the entire meaning of the transmission without the receiver knowing. <S> Ex. <S> “Descending one five thousand” is a different meaning with different consequences than “Descending five thousand”. <S> 25 spacing is used in the United States. <S> Europe and other countries use 8.33 spacing. <S> All NEW avionics and airband transceivers that I know of feature user selectable spacing. <A> From Wikipedia : <S> Channel spacing for voice communication on the airband was originally 200 kHz until 1947, providing 70 channels from 118 to 132 MHz. <S> Some radios of that time provided receive-only coverage below 118 MHz for a total of 90 channels. <S> From 1947–1958 the spacing became 100 kHz; from 1954 split once again to 50 kHz and the upper limit extended to 135.95 MHz (360 channels), and then to 25 kHz in 1972 to provide 720 usable channels. <S> On 1 January 1990 the frequencies between 136.000 and 136.975 MHz were added, resulting in 760 channels. <S> Increasing air traffic congestion has led to further subdivision into narrow-band 8.33 kHz channels in the ICAO European region; all aircraft flying are required to have communication equipment for this channel spacing. <S> Outside of Europe, 8.33 kHz channels are permitted in many countries but not widely used as of 2012. <A> As already stated in other answers, the narrower the spacing, the more channels which can be fit within a given spectrum. <S> Channels have to have some amount of spacing because signal modulated onto a carrier will create sideband ; the exact nature of the sideband depends on the signal to be modulated and the type of modulation. <S> In general, some sideband is inevitable because it actually represents the input signal. <S> Rejecting sideband in a receiver generally excludes information (lower quality of demodulated signal). <S> In order to allow for multiple channels to co-exist, transmitters must confine their sideband emissions so as not to interfere with transmissions on adjacent channels and receivers have to be capable of recovering the transmitted signal with acceptable fidelity; this means that receivers have to accept some amount sideband while rejecting frequencies too far away from that assigned to the channel. <S> The progression from wide spacings to narrower spacings reflects technological improvements in radio design; transmitters improve to confine their emissions to narrower sidebands while receivers improve to recover acceptable signals from the narrower transmissions. <S> Congestion of the RF spectrum is what drives to need to increase the number of channels, either by allocating new portions of the spectrum or by fitting more channels into the existing spectrum.
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If you are referring to 25 kHz spacing versus 8.33 kHz spacing, it gives more channel options in radio transceivers.
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How often do GA pilots use the Autopilot approach feature while landing? While flying in simulations, I found that using the Approach feature is very beneficial for riding the glide slope (clear weather or not), however, while watching videos of GA pilots, I do not see it performed too often. Which brings me to my question as to whether that is a common practice, or if it is frowned upon unless it is necessary for a safe landing? <Q> It's a perfectly acceptable practice, provided you disengage the autopilot upon reaching minimums and hand <S> fly it the rest of the way. <S> Some manufacturers, like Cirrus, recommend flying a coupled autopilot approach. <S> I won't sit on the fence about this. <S> Learning how to fly coupled autopilot approaches are fine, but I insist all my students learn how to hand fly approaches, both as part of their initial instrument training and for all instrument proficiency checks I administer. <S> If I were an examiner I would insist on seeing instrument applicants demonstrate hand flown approaches on their checkrides as well. <S> Autopilots are great but their use can begin to atrophy their flying skills and it can come back to bite them, particularly in an emergency. <S> As to the exact numbers of GA pilots who fly coupled autopilot approaches, that's probably going to depend on the pilot and the equipment in his/her aircraft. <A> The question as it currently stands in the headline <S> "How often do GA pilots use the Autopilot approach feature while landing?" <S> is hard, if not impossible to answer due to lack of relevant statistics. <S> As for <S> the matter(s) raised in the body of the question, is and should the autopilot be used on approaches in GA , here's how I see it, plain and simple: <S> You must be able to fly the plane manually, no matter what the situation is. <S> You should be able to fully understand and operate any systems your aircraft provides: gps, autopilot etc. <S> Proficiency of both should be practiced in order provided above, former being necessary for survival, and latter providing ease of operation and extra safety when used properly. <S> I won't give examples of ratio between practising 1 and 2, as this varies hugely from one person to another. <S> P.S. the best mindset for GA pilot is to consider every flight a training flight. <S> Set more goals than just fly from A to B to A . <S> The most dangerous GA pilots are the ones who know it all and therefore no longer need to practise. <S> They are as good as dead. <A> In the non-student GA world, I would say not very often. <S> Maybe 1 in 6 approaches as a guess and from personal experience. <S> If a pilot is flying actual IMC, they may fly a coupled approach as a safety measure. <S> Most non-commercial GA pilots will avoid flying actual IMC in most cases as a rule. <S> Some will fly actual IMC, when the conditions are not too bad, to stay sharp. <S> Others will only fly their required 6 approaches in VMC. <S> Either way, they will mainly hand fly the aircraft for the sake of staying proficient. <S> I’ll usually make sure to fly 1 of my 6 on autopilot. <S> As far as the videos mentioned, how many of them were from training flights? <S> More emphasis will probably be made on hand-flying on training flights. <S> The DPE on my Checkride required one approach be done using autopilot. <S> All of the others were required to be hand-flown. <S> Then again, this is speculation on the general aviation community based on my little microcosm of it. <S> The sample size is only in the dozens.
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As long as you are able to take over from any system, the AP for instance, at any time, no-one should (probably will though) frown upon using it. Pilots with autopilots installed are probably going to be much more likely to use them and be more comfortable flying approaches this way.
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Why Didn't the USSR Build An X-15? In the history of aerospace engineering in the United States, the X-15 is lauded as a critical and necessary step on the path to manned spaceflight. Throttle-able chemical rocket propulsion systems, reaction controls, and pressurized flight suits were all major design features of the X-15 that eventually found their way into future successful spacecraft. Given the obvious resources the USSR put into the space race and their numerous successful missions, why did they never build a hypersonic space-plane akin to the X-15? <Q> I like the X-15, it was certainly an amazing airplane, but the truth is there were few benefits to the space program from the X-15. <S> It was far from a critical or necessary step: <S> The Mercury space suit was a direct derivative of the BF Goodrich Navy Mark IV , which had been in use for years. <S> It wasn't developed for the X-15 <S> They were orders of magnitude stronger for one thing, used different fuels and completely different designs. <S> Throttle-able rocket propulsion systems weren't new <S> The X-15 thermal protection system was of no use to the space program, which had to deal with far higher temperatures <S> There were some benefits: <S> It was a good source of astronauts: several pilot from the program went on to the NASA programs, including Neil Armstrong Data from the X-15 missions were used in the <S> X-20 <S> Dyna <S> Soar spaceplane which never flew, but it eventually morphed into the space shuttle <S> As to why didn't the Soviets make one, they didn't need it. <S> Their manned space program built off of their ICBM development efforts which were successful. <S> If the US hadn't built the X-15 <S> the manned space program would most likely never gone the space shuttle route, but that wouldn't have been any sort of deal breaker. <A> I'll complement GdD's answer from a slightly different perspective. <S> In the history of aerospace engineering... <S> Wait, there is a problem right there. <S> Due to various historical reasons, there was no aerospace industry in the USSR, at least the way it is known in the West. <S> The very word "aerospace" was almost never used before the 90s. <S> Aeronautics and space were much more separated than in the US. <S> There were no companies that dealt with both the way Boeing or Lockheed did. <S> (Though some were forcibly switched from aviation to space in the late 50s). <S> Space industry, especially at the early stages, had more affinity with artillery than with aviation. <S> This involves not only the formal bureaucratic subordination, but the whole mentality, from design to testing. <S> In this scheme of things, rocket designers wouldn't even think of building an 'aeroplane' (and X-15 is undeniably an aircraft) for testing. <S> They would rather shoot a few more rockets. <S> Especially given the preferrential supply of resources to the space industry. <S> There were some later attempts from the aeronautics industry to get involved, but none were remarkable (until, perhaps, Buran ). <A> The X-15 was an extension of the X program, started in the 1940s, to continuously push the speed envelope of aircraft through the sound "barrier" , and the thermal "barrier" beyond it. <S> Manned space flight, requiring rockets with much more thrust for far longer, simply is in another league, and was founded in the ICBM programs of both the US and USSR, which owed much of its foundation to the pioneering work of Goddard, and the development and scale up (including the all important turbo pump) of team von Braun. <S> Recovery systems from these flights were, and are, capsules . <S> It is rather dumb to haul an airplane into space when payload to orbit costs are measured in thousands of $ per pound. <S> The Space Shuttle was an awesome technology demonstrator, but never succeeded as a low cost replacement for ordinary rockets to move cargo to orbit , but remains a viable option as a means to return cargo and crew from orbit . <S> So, although the X-15 did reach the edge of space on some of its flights, and did use control thrusters, it was much more an airplane, and should be more than welcome as a subject for readers to enjoy on Aviation Stack Exchange. <A> There were three competing ways to space pursued in the US while in the USSR everything was centrally managed, so they followed only the way that Konstantin Tsiolkovsky had first proposed. <S> What were those three ways? <S> The US Navy used a home-grown team to develop a rocket at the Naval Research Laboratory . <S> Their Vanguard rocket failed several times, however, before it worked as designed. <S> The US Army relied on a bunch of German engineers who had worked for the Wehrmacht artillery before 1945. <S> Fittingly, they were housed in the Redstone arsenal grounds of Huntsville, Alabama. <S> Their Juno rocket was used for the first US satellite launch after being placed in storage for almost a year so the Navy team could try first. <S> The US Air Force wanted to use a winged craft to get into space. <S> For them, rockets were a temporary shortcut and several, rocket-powered test aircraft were developed in order to get closer to spaceflight. <S> While also developing the Atlas rocket, the US Air Force in cooperation with NACA, later NASA, ordered several X-planes to test access to space and re-entry with a winged vehicle (X-2, X-15, X-17, X-20, X-23, X-24, X-30, X33, X-34, X-37, X-38, X-40, X-41 and the list goes on). <S> The planners in the USSR never planned something like the X-15. <S> Also, when the X-15 flew, they saw no need to do something similar.
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Great question, but no, the X-15 was not a "critical and necessary step on the path to manned space flight" at all, it was used to test the feasibility of sustained and controlled hypersonic flight of an aircraft at very high altitudes and speeds. The rockets used in the space program were completely different from the X-15.
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Why would 2 aircraft fitted with the P&W PT6 Engine have different top speed? Why can the Quest Kodiac and Cessna Caravan not exceed 200 knots? PT6 from Pratt and Whitney in other implementations like Epic E1000 and Pilatus PC12 can cruise at over 300 knots. The Kodiac and Caravan are advertised at only ~180 knots. Why is there such a difference? Is the fixed landing gear the problem for such a limitation on speed? <Q> The P&W PT6 comes in many different varieties. <S> The smallest PT have 500hp while the largest have 1700hp. <S> It is not the "same engine" as you state in your question. <S> The standard Caravan has 675hp while the other aircraft you mention have 1,200hp. <S> That alone can account for the major difference in performance. <S> There is no reason to expect similar speed or performance. <A> Even if the installed engine version was identical (which, as @MikeSowsun noted, is not always the case), different types have different weights, drag profiles, and may have different propellers fitted -- all of which affect top level flight speed, as well as rate of climb, takeoff performance, maximum load capacity, range; the list goes on. <S> It's like asking why a canoe is faster than a rowboat -- they have the same engine (a single human), but that's where the similarity ends. <A> That’s kind of like saying why can’t a Ford F150 Raptor keep up with a Ford GT sports car on a race track? <S> Both have the same engine, don’t they? <S> It’s a different airframe designed around different performance criterion. <S> Some aircraft eg a C208 are designed and optimized to operate from short, rough fields hauling cargo on short hauls. <S> Others eg <S> a Piaggio P.180 are designed for high speed cruise at high altitudes and extended endurance profiles. <A> When considering top speed vs power (thrust), drag is the deciding factor. <S> Lower induced drag means higher top speed, but also less lifting ability and higher landing speed. <S> Retractable slats, flaps, and landing gear all serve to help increase top speed by reducing drag and to improve take-off/landing performance (particularly landing gear). <S> The Flyak is a good example of how drag reduction can improve top speed. <S> It's aerodynamic equivalents would include variable geometry wing concepts, as well as slats and flaps. <S> Landing gear would not be needed here.
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Fixed gear and struts also add to an increase in drag and a reduction in speed. The bottom line is they are different aircraft, with different engines, designed for different roles.
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How does the DA 40 NG automatically control the mixture, pitch and power by just providing one throttle? I'm a student pilot and here at my school we have the older gen DA40s which have individual lever for mixture, pitch and power. I was looking at this video of the DA40 NG, and got quite curious as to how everything from prop to mixture is automatically controlled, and on top of that you don't need to do any run up checks! Tried using google but nothing really came, so I thought this would be the right platform to ask and satisfy my curiosity. <Q> According to Diamonds website the NG engine is a: <S> Austro Engine AE 300 turbocharged common-rail injected 2.0 liter diesel engine with 168 hp and EECU single lever control system <S> The prop is a: 3 blade MT hydraulic constant speed propeller features advanced blade geometry for efficient performance, low vibration and noise. <S> It is automatically controlled by the engine’s digital engine control through a conventional hydraulic governor. <S> From the sounds of it, it is as close to a full FADEC (Full Authority Digital Engine Control) unit as you can get <A> As stated above in the last answer, it’s turbodiesel powered. <S> Like the DA-42 and DA-62, the engine is basically power by wire, using a primary and secondary Engine Control Unit (ECU) computers, each with a dedicated battery backup, both for engine control and control over the constant speed propeller. <A> Aside from the fact that the engine is computer controlled... <S> the reason you don't have mixture control is <S> Diesels don't use that . <S> Gas engines need to breathe a stochiometric mix of air and fuel, i.e. proportioned correctly <S> so there's just enough fuel for the oxygen admitted. <S> Too fuel-lean <S> and it won't burn. <S> Power is controlled by partially blocking the air intake with throttle plates (hence, vacuum). <S> Getting the mix stochiometric under all conditions is a hard job, and that's what the carburetor does. <S> The mixture control helps you fine tune what the carb cannot. <S> In a diesel, you gulp in a full shot of air <S> (throttle plates: Gone ), and compress to a high compression ratio and high heat. <S> This means when fuel is injected, combustion is both certain and spontaneous. <S> So they don't need spark plugs, and can happily run lean (mixture control: Gone ). <S> Spontaneous means the engine intake drawing in a fuel-air mixture is out of the question; it would ignite too soon. <S> The engines are direct injection. <S> Diesel power is controlled solely by how much fuel is injected per cylinder. <S> That is done at the fuel injection pumps. <S> One pump per cylinder that pumps at the appropriate time in the stroke, driven by a cam. <S> Each pump has an adjustment that decides how much fuel is injected. <S> And this is controlled by a "fuel rack" which sets all pumps the same, and the fuel rack is the "throttle". <S> I always thought diesel's simplicity would make it ideal for aircraft, but the high compression ratio requires stronger cylinders and makes diesel engines heavier, and that's an issue. <S> Of course nowadays, in their mad pursuit for EPA Tier 4 emissions, they use computers. <S> One common trick is to eliminate the mechanical cam and rack with sensors and EFI to inject at the right time. <S> But they don't have to do that. <S> It's a reliability vs emissions numbers call. <A> Other answers concentrated more on the 'mixture' and FADEC side of things. <S> I'll show what it does with the prop speed. <S> This is actually simpler and is explained right in the flight manual (p. 7-25). <S> The prop speed is pre-programmed to follow the engine lever: <S> So, it only uses highest RPM at takeoff power, and then reduces it at cruise settings. <S> At very low settings it 'unloads' the prop by commanding higher RPM (which it may not reach). <S> This may increase windmilling drag though, and this is a common complaint about automaitc prop control. <S> It is not necessary to have FADEC for such programming. <S> Cirrus aircraft use mechanical linkages to achive a similar control.
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It is controlled by a computer module just like your modern fuel injected car.
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Does the tailplane have a positive/negative camber? I've read that the tailplane produces negative lift, so does that mean it would function like an inverted wing (has negative camber)? The image below is the best illustration I could come up with. Also, is negative lift and tail down force the same thing? <Q> The tailplane should produce less lift than the main wing, for pitch stability. <S> That is to say, its lift is negative relative to the wing lift. <S> Its lift need not be wholly negative (pointing down), although it usually is during takeoff and landing. <S> But yes, as a first approximation, the direction of camber matches the direction of lift. <S> Also yes, negative lift (at the tail or anywhere else) can be called downforce (at the tail or anywhere else). <S> Here is Peter's explanation . <A> Most tailplanes (except for specialist applications, like endurance designs in model airplanes) have a symmetrical airfoil, whether thickened or effectively a flat plate. <S> Camber of any sort is unusual in tailplanes for full size aircraft -- except as it might be incidentally produced by elevator trim, and in that case, it might be either upward or downward, depending on the trim requirement at any given speed and CG location. <A> This is mostly in combination with powerful flaps on the wing so the tailplane will continue to work with flaps extended, when it needs to develop a relatively high downforce (which is indeed the same as negative lift). <S> The extended wing flaps result in higher wing downwash so the tail "sees" a more negative angle of attack. <S> By cambering the tail airfoil, it will tolerate more negative angles of attack and its minimum lift coefficient is lower than that of a symmetrical airfoil. <S> I know it is hard to see, but this Do-228 tailplane really does have negative camber (picture source ). <S> The PZL Wilga has a symmetrical tail airfoil but uses an inverted, fixed slat at the leading edge of its elevator (picture source ). <S> The A380 uses negative camber at the root of the tail, too, like most airliners (picture source ). <S> To keep isobars aligned with chord lines in a swept wing is also a reason for negative camber at the root. <A> A few constructions, such as the Zenith CH 701 STOL, have horizontal stabs with non-symmetric, inverted airfoils:
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Indeed, the airfoils on many horizontal tail surfaces do have negative camber.
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What is "company compensation fuel" and "pad fuel"? I tried to find the definition of these fuels but I could't. Does anyone know about company compensation fuel or pad fuel?In which document can I find the definition of these fuels? <Q> Company Compensation Fuel <S> This is a term, which seems to be used by Korean Air. <S> They define it on their website: ▶ <S> Company Compensation Fuel fuel to minimize abnormal flight occurred. <S> Based on this, fuel consumption performance is modeled for a certain period of time, and based on this, the amount of fuel repeatedly consumed excessively compared to the flight plan is added. <S> ( koreanair.com , translated by Google) <S> So this is fuel added based on the airline's experience (hence company ) for typical fuel use on a given route. <S> Pad Fuel <S> I have never heard this term and Google also does not find anything related to aviation. <S> Is it possible <S> this was a translation? <S> If so, could you add the original term and where you heard about it? <A> I suspect the "pad fuel" might refer to conditions where deicing is needed. <S> Time spent on deice pad with engines running leads more fuel consuption than a normal taxi to holding point would. <S> Since this is an easily indentifiable situation with predictable effect on fuel consumption, it might be that this would be referred to as "Pad fuel" . <S> But: as google comes up with absolutely nothing, I highly doubt my own answer. <A> <A> PAD fuel is company specific and typically applies to an abnormal event taking place at or near a predefined point; e.g., ETP during ETOPS. <S> For example: If a depressurization event were to occur and a subsequent decent commenced, PAD fuel would be that in excess of minimum GO/RETURN fuel to reach facilities named on either side of an ETP under reduced efficiency. <S> It’s just another dispatch contingency similar to the aforementioned compensation fuel and is used in the same colloquial context as if supplementing or “padding” one’s bank account.
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While I have no specific knowledge of these terms being used together, my first thought was that "Pad Fuel" would be fuel gotten from the local pad, and "Company Compensation Fuel" would be fuel that you purchase while away and get reimbursed for, or compensated.
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What's the meaning of "the break is a level" in a recovery operation of an aircraft carrier? The break is a level, 180° turn made at 800 feet (240 m), descending to 600 feet (180 m) when established downwind. Landing gear/flaps are lowered, and landing checks are completed. (source: wikimili.com ) <Q> "Level" isn't a noun here--it's not that the break is a level. <S> Level is an adjective describing the kind of a turn. <A> The "break" is where the aircraft enters the landing pattern. <S> The aircraft carrier tries to time entries into the break such that aircraft are landing in 15-20 second intervals. <S> Until you "break" you are in a holding pattern around the aircraft carrier. <S> Entering the "break" is getting into the pattern to land. <S> When they say "the break is level" it means the altitude is maintained during the turn to enter the pattern, so it is a "level turn". <S> Here is a graphic that illustrates the level turn, then the descent when established on downwind. <S> Source: Wikipedia <A> The break is a 180° turn from the upwind to the downwind in the landing pattern which allows for the separation of elements in a formation and spacing of individual aircraft for recovery. <S> Typically the break (for a Case 1 recovery) occurs on the upwind leg at 800 ft AGL, 1 NM DME ahead of the ship, at 350 kts. <S> The lead aircraft breaks formation, turning to enter the downwind with his wingman continuing on in the upwind, making the turn to the downwind 15-18 seconds later. <S> This allows for an approx. <S> 45 second spacing between aircraft in the downwind and final approach legs to ensure spacing for each jet to recover, taxi clear of the LA, and reset the arresting gear for the next jet.
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A break is a turn; that turn is a level turn (neither descending nor ascending), and a 180 degree turn, and it is made at 800 feet.
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Why can’t level D simulators produce a G-force effect? From what I know so far, simulators can’t simulate this feeling, I’ve heard some say it will never be possible. Is that true? There’s really no way of producing this in a simulation? <Q> They can produce sustained G-forces, by tilting the sim without the occupants noticing. <S> Of course, this tilting of the 1G gravity vector is limited to practical angles of about 45°, producing 0.7G of simulated sustained horizontal acceleration. <S> Vertical sustained acceleration is a different matter altogether: the 1G is always already there and can only be reduced by tilting the sim, while in manoeuvres with increased load factor we're looking to increase beyond 1G. <S> Fortunately the inner ear sensors can be tricked to an extent: they are very good at detecting acceleration onsets but get flooded by sustained acceleration inputs. <S> Our brain seems to rely on the inner ear for detecting the first onset of acceleration, then on our peripheral vision to read the motion velocity. <S> So if we heave the sim rapidly and show the movement on the visual, we cannot detect very readily if we're not pressed down by g-forces anymore after some time. <S> Image source <S> Level D simulators are for civil aviation training, which teaches how to limit load factor. <S> Military sims are a different kettle of fish, as mentioned in this answer. <S> G-seats like depicted above provide cues to our body skin sensors, as do G-suits. <S> Centrifuges can of course produce sustained g-forces, and they do exist, used by the military to train sustained g flying and by medical facilities to check how long a person can remain conscious. <S> A combination of a centrifuge with a civil 6-DoF system is not really possible for realistic acceleration simulation. <A> The only G forces the simulator can simulate are sustained lateral forces, which you feel when it tilts, and very limited short vertical and lateral accelerations. <S> A tilt aft feels like acceleration/climbing, a tilt forward feels like deceleration/descending, and tilts to the side <S> feel like you are skidding. <S> The only vertical accelerations the sim can reproduce are short bump sensations and other brief vertical motions made possible by the ability to of the hydraulic jacks to jerk the machine up or down briefly a few feet. <S> The sim is also good at doing short lateral jerking motions that you would feel when touching down in a crosswind with a bit of crab in. <S> The most realistic effects are the acceleration/braking effects, especially takeoff and landing sensations, and short term vertical and lateral effects meant to simulate bumps and things like flap deployment, and pavement seams, side movements while rolling on the ground, that sort of thing. <S> The most unrealistic effect is the round out and flare to land, because the sim can't reproduce the mild G increase when you pitch up <S> and you get a weird kind of floating sensation in your head when you do it (at least I did). <S> Because the force simulations are limited, once you've done a fair amount of training in them, you start to become more aware of the odd disconnects between the view on the screen and the seat of the pants sensations, and then you start to become more aware of the faint sound of the hydraulics running outside, which spoils the effect even more, and you're less apt to get mentally lost in it and forget you're not in the real a/c, except when you're put into extreme scenarios that are close to overwhelming your brain. <S> You could simulate sustained G forces by having the sim gimbal mounted in a massive centerfuge <S> but it's not worth the expense to get that extra realism <S> (they are expensive enough as it is and no airline would pay for it). <A> The short answer is: because the room containing the simulator has a ceiling, floor, and walls, through which it is desired that the simulator not travel. <S> Since the integral of acceleration is non-zero, acceleration implies velocity which implies distance travelled. <S> For rooms of a reasonable size, this implies that only very limited accelerations may be realistically simulated without bursting through the physical walls of the room containing the simulator. <A> The ACME Worldwide Enterprises motion cueing simulator seat CAN produce a G-force affect. <S> They can be used with military or commercial simulators and utilize technologies placed inside a replica seat's back pan, seat pan, shoulder and lap belt harnesses to simulate g-onset and up to 1.8G sustained g-cues. <S> The signal to the seat comes from the aircraft flight (acceleration) model so the signal to the visuals (and platform motion if used) is the same signal to the motion-cueing seat.
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The sim cannot reproduce sustained turning G force sensations and it can't reproduce the long term turning effects on your inner ear because it can't rotate in a sustained way.
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If pilots in a A320 or 737 had a dual engine failure, would they add flaps for the landing? Would this not be smart to do because you may come in a little fast, therefore the flaps would send you back up? Or would you absolutely want flaps in this situation <Q> Flaps steepen the descent angle - in other words, you run the risk of falling short of the runway. <S> So in a glide you keep the flaps up until you can be certain of making the landing point. <S> Once the landing is guaranteed, you can then deploy gear as well as flap to slow down as much as possible - being aware that these actions will further reduce the gliding range, so constant reevaluation is required. <A> That would be up to the discretion of the flight crew, what forced landing site they selected, approach route, etc. <A> You would certainly prefer to have flaps available in order to reduce landing speed. <S> If so, the pilot in command has discretion whether using flaps is appropriate to the situation. <S> Unfortunately, the loss of all engines may prevent flaps from being deployable. <S> In two of the most famous airline no-engine landings I can think of, the Gimli Glider and Air Transat Flight 236 , flaps could not be used due to lack of hydraulics. <S> In the case of US Airways Flight 1549 , however, the APU was used to provide hydraulic pressure (which was impossible in the other flights mentioned, since there was no fuel left in those cases). <S> Partial flaps were used in the ditching.
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Typically deployment of flaps in a forced landing scenario will only be done once the airplane is guaranteed to make the landing site by gliding in that landing configuration.
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How hot do internal parts of jet engine get? How hot does a jet engine get? I'm interested in the temperature of the parts, not of the exhaust or combustion. If you took temperature of an engine after a flight across the Pacific Ocean what are temperatures of stationary and movable parts? A car engine block may be 250 degrees Fahrenheit (120°C). I'm thinking of how to modify the basic architecture. <Q> This parameter is called Turbine Inlet Temperature (TIT) Turbine Inlet Temperature (TIT) is the temperature of the combustion chamber exhaust gases as they enter the turbine unit. <S> The gas temperature is measured by a number of thermocouples mounted in the exhaust stream and is presented on a flight deck gauge in either degrees <S> Fahrenheit or degrees Celcius. <S> Essentially it's the temperature going out of the combustion chamber, representing the highest temperature the turbine would face. <S> Here's a figure showing how we are doing recently. <S> So we are at around 1800K now and may reach 2000K soon. <S> For the temperature of the actual part under cooling, here is the current status of materials: we are at around the 1350K mark and may approach 1400K soon. <A> Depends on the section of the engine in question. <S> On modern, high performance aviation gas turbines, the high pressure turbine inlet temperatures are reaching nearly 3,600° F during full power operation. <S> Exhaust Gas temperatures in the jet pipe just aft of the last low pressure turbine stage <S> are in the neighborhood of 1,000° F. Air exiting the high pressure compressor section will be around 500° F. <S> A little basic thermodynamics will quickly demonstrate that the hotter you can operate the gas at the beginning of its expansion through the turbine section of the engine, the more efficient the engine will be. <S> This increase in temperature is, of course limited by the material properties of the metals and composites used to manufacture these engine parts. <S> Jet engine turbine sections are usually manufactured from novel nickel-cobalt and titanium superalloys using novel single crystal casting techniques for maxiumum structural strength. <S> In addition, they also make use of compressor bleed air for use as a boundary layer to prevent direct contact between the walls, stator and rotor blades and the high temperature gases. <A> Compressor exit temperature and turbine inlet temperature are the hottest regions, front and back of combustor respectively. <S> However, it is rare that TIT is directly measured. <S> Most times the inter turbine temperature (ITT - ARP station 4.5) and <S> station 5 <S> (EGT - exit of the low pressure turbine, back of the core stream) are measured and mathematical and thermodynamic models back out what the TIT would be. <S> The cockpit displays EGT, not TIT. <S> But referencing the graph above, the trend is real but it’s not actually measured directly. <S> Too hot back there.
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The 'hot section' of a jet engine gas core, which consists of the isobaric combustor, high pressure turbine and low pressure turbine, by far, operates at the highest temperatures.
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What happens when a GA pilot squawks 7500? If you were to put code 7500 into your transponder in a small general aviation aircraft, and you were in a rural area with no one around, and you did not have enough fuel to get to any city, what happens? Would they shoot you down? {edit what I meant was if you were being Hijacked and you on purpose sqacked 7500 <Q> Who would shoot you down and why? <S> You are in the middle of nowhere. <S> Who are you endangering? <S> ATC would try to contact you to ascertain your actual condition. <S> You may have accidentally put in the wrong code. <S> They would then offer assistance if needed. <S> If it was a kidnapping situation, all they could do is follow or track you until you land. <S> You are not going to get far. <S> Even if you went to another country close by, you can still be tracked and local authorities alerted. <A> A distress code is not a 'shoot me down' signal. <S> ATC will see the code, and will try to establish contact. <S> If the pilot wasn't with ATC already, they should be on the guard frequency at the very least. <S> For USA, the AIM ( Distress and Urgency Procedures ) provides the following: <S> If the pilot replies in the affirmative or does not reply, the controller will not ask further questions but will flight follow, respond to pilot requests and notify appropriate authorities. <S> Regarding the use of force, that is not the ATC's call or scope. <S> If it's an accidental 7500 (changing the code means the pilot is in touch with ATC, unless they're playing around), the AIM ( Services Available to Pilots ) provides information on how to avoid that: When making routine code changes, pilots should avoid inadvertent selection of Codes 7500, 7600 or 7700 thereby causing momentary false alarms at automated ground facilities. <S> For example, when switching from Code 2700 to Code 7200, switch first to 2200 then to 7200, NOT to 7700 and then 7200. <S> This procedure applies to nondiscrete Code 7500 and all discrete codes in the 7600 and 7700 series (i.e., 7600-7677, 7700-7777) which will trigger special indicators in automated facilities. <S> Only nondiscrete Code 7500 will be decoded as the hijack code. <S> Related: <S> What prevents a passenger from hijacking a private jet? <S> And the Mountjoy Prison helicopter escape <S> is the only incident I found where a light aircraft was hijacked. <A> If you enter a 7500 code in a transponder, I'd expect the authorities would almost certainly intercept you with instructions as to where to proceed to and land. <S> They have no idea as to your particular situation other than you're transmitting an aircraft hijacking emergency code <S> and they are not going to take chances. <S> As to using deadly force against you, it is an option, provided you are posing an immediate danger to the public or national security.
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The most likely scenario is fighter interception followed by instructions as to where to go and land where ground based law enforcement can take control of the situation.
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Why do modern aircraft tend to have angular tails? In the WWII-era and earlier, many (most?) planes had rounded tails, even high-speed and high-performance fighters such as the Bf 109 K, Ta 152 (though it is more square-ish), P-38, Hawker Typhoon, and even the F-80. A notable exception to this trend is the P-51. Modern aircraft, on the other hand, tend to have very angular tails. High speed fighters, to airliners, even relatively slow aircraft like the Cessna 152 or Piper Archer have very angular tails. What is the reason for this change in trend? <Q> While the design is very slippery for speeds of Mach < 0.6 or so, it is more difficult to manufacture, which is why, near the end of the war, Spitfires had the 'clipped' wingtips as opposed to the original pure elliptical planforms. <S> The modern low aspect, sweptback, trapezoidal tail design is a better choice for higher airspeeds and supersonic flight ie Mach > 0.8 and mitigating flight control flutter due to compressibility effects, the same reasons we use sweptback wing. <S> Note as well that modern fighters use the same kind of planform for their wings and tail planes as they offer a compromise between acceptable supersonic aerodynamics and good trans sonic maneuverability. <A> Aside from any subtle aerodynamic benefits of elliptical surfaces vs straight tapered ones, the move away from rounded profiles was mostly for ease of manufacture. <S> A rounded profile has much more complex lofting demands, especially for the stabilizer part, and is more expensive to produce. <S> Properly done, there are going to have to be compound curves, requiring skins to be stamped in 3-dimensional dies, which has to be done in an annealed state and heat treated after, with rib flanges bent in mating contours. <S> Compare that to a straight edge surface that only needs skins with simple 2 dimensional bends that can usually be done in the final heat treat state (for larger radius bends). <S> Some light aircraft, like the Cessna 170 , were able to get rounded looking profiles with mostly flat skins by using just a compound curve formed leading edge skin. <S> But even here going to a straight tail <S> eliminated that requirement and a stabilizer <S> could be skinned with a single wrap instead of a separate upper and lower or left and right skins and a die stamped compound curve leading edge skin. <S> As well, think of the reduction in rivet count and labour hours in general. <S> Over time the straight edged shape also came to be associated with modern, so "modern looking" and "cheaper" in combination become pretty hard to beat and round <S> surfaces disappear except in special cases. <A> Yes, in the case of light aircraft, backward slanting tails were the direction of marketing departments, not aeronautical engineers. <S> The reason they are not good is that in low speed, high angle of attack such as the pre-landing flair, the rudder is actually increasingly canted out of the wind. <S> It's rearward slant adds to the angle of attack to make the projection of the rudder's area in in the direction of flight smaller. <S> One counter example is the Mooney M20 series series. <S> These aircraft have vertical leading edges on the vertical stabilizer, and the rudder actually slopes forward . <S> This gives the rudder a larger projection in the landing flair, resulting in it having increasing effectiveness. <S> Whether or not it makes the Mooney M-20 series of aircraft look faster is irrelevant. <S> Mooney airframes are noted for low drag, resulting in high speed at lower fuel consumption compared to most other light aircraft designs.
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The rounded or elliptical design was found to be the cleanest aerodynamically in non-compressible subsonic airflow, which is why it's very common on aircraft of that era.
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What are the least powerful airplanes that ever flew? What manned airplanes have achieved flight with the least powerful engines (no gliders!), and what was their top speed? Im sure I've heard of an airplane with an 8hp engine capable of exceeding 120 MPH airspeed <Q> There are a number of human-powered aircraft (list here ). <S> For the Gossamer Albatross , we have <S> In still air, the required power was on the order of 300 W (0.40 hp), though even mild turbulence made this figure rise rapidly. <S> As far as top speed: Allen completed the 22.2 mi (35.7 km) crossing in 2 hours and 49 minutes, achieving a top speed of 18 mph (29 km/h) and an average altitude of 5 ft (1.5 m) <A> Sailplanes employ zero horsepower by conventional reckoning, though an alternative definition can be proposed using the component of the aircraft's weight that acts parallel to the airspeed vector as the thrust-like force. <S> Anyway, the world records for sailplane flight appear to include 2191 km as greatest free distance along a course involving three or fewer turnpoints, and 22657 m as maximum absolute altitude. <S> Source: <S> fai.org/page/igc-records <S> OK, I thought the original question said "aircraft"; I now see "airplane". <S> Does "airplane" always exclude "glider"? <S> Originally, the "plane" in "airplane" referred to the "planing" action of the wing surface, and had nothing to do with the presence or absence of a motor, though there may be no specific examples of the word historically being used in reference to gliders. <S> Didn't see the "no gliders!" <S> when I created this <S> answer-- <S> sorry! <A> Even though at 4 x 13kW its max rated power (70hp) is higher than the other answers, Solar Impulse flew almost 5 thousand miles non-stop during close to 5 days. <S> It did not typically fly anywhere close to its max rated power in order to conserve energy that it would have to spend during the night. <S> Wikipedia lists the specs as: <S> Maximum speed: 140 km/h (87 mph) <S> Cruise speed: 90 km/h (56 mph) <S> 60 <S> km/h (37 mph) at night to save power Service ceiling: 8,500 m (27,900 ft) with a maximum altitude of 12,000 metres (39,000 ft) <A> This is of course much higher than the human-powered Gossamer Albatross in Eugene Styer's answer , but the Wright Flyer , "the first powered, heavier-than-air machine to achieve controlled, sustained flight with a pilot aboard", used a 12 horsepower gasoline engine which is a bit under 9 kW. The longest of its 4 flights was 260 m, and it was apparently so light that "a heavy gust picked up the Flyer and tumbled it end over end, damaging it beyond any hope of quick repair". <S> Later versions used more powerful engines. <A> The lightest remote control airplane I could find is 0.225g (0.01oz). <S> Wing span 71 mm. <S> Length 70 mm. <S> (about 3") <S> I estimate it used a few hundredths of a watt. <S> https://www.rcgroups.com/forums/showpost.php?p=11048403&postcount=1 <S> That was back in 2008 though, so they've probably done better since then. <A> The twin engined Columbian Cri cri might be a contender: each of the single cylinder piston engines were about 15hp. <S> Cruising speed is 190km/h. <S> Wikipedia article
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Some self-launching powered hang gliders and powered paragliders/ paramotors intended for soaring flight must be close contenders for the answer to your question, as some of them have rather weak engines and are barely able to climb in the absence of an updraft despite overall light weight.
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Why are no recent small aircraft designed to be "characteristically incapable of spinning" as the Ercoupe was? I'm a student pilot at a flight school that primarily flies RV-12s as a trainer. We had one day that through a booking error meant that all the RV-12s were booked so we had to use their Ercoupe 415-C instead. I was surprised at how easy the plane was to fly and asked my CFI about the "characteristically incapable of spinning" placard on the front panel. He explained that the rudder pedals weren't necessary because the plane maintains coordinated flight by connecting the ailerons to the rear rudder. I think this is an amazing innovation for the Ercoupe and I'm surprised it's not a design that I can find on any modern small aircraft designs. Maintaining coordinated flight with rudder pedals isn't a complicated task for a trained pilot but it is another task that the pilot needs to perform. It seems like removing flight tasks from the pilot would make for a safer aircraft so why do manufacturers not include designs similar to Ercoupe's models? Is it a weight/cost/drag issue, or are spins not as huge of a killer as they were in the 40s-60s? <Q> The coupling between the ailerons and rudder are designed such that they avoid uncoordinated turns as you described. <S> However, this occurred at the expense of control in other flight conditions. <S> In fact, there are situations where you need to deflect the rudder without roll input, you need to deflect the rudder more than the preset coupling, or in a manner that is opposite to the preset configuration. <S> For example, if you turn right, the system will add right rudder to keep the airplane coordinated. <S> But if you want to do a forward slip, you may perform a left hand roll, but with rudder all the way to the right. <S> The system would be incapable of performing this maneuver, meaning you can't fly in high winds with the system installed. <S> This is fine if you live in an imaginary place where the winds are always favourable. <S> As a result, a common modification on the Ercoupe is to disconnect the coupling between the rudder and ailerons... <S> Edit: I also wanted to add that spins are recoverable, within reason, by a trained pilot. <S> For some planes, you are simply forbidden to intentionally enter a spin as a remedy to its inability to recover from a spin! <A> Rudder pedals are used for more than keeping turns coordinated. <S> Forward slips for crosswind landings, slips to increase drag during descents, and reducing the tendency to weather-vane during <S> cross-wind taxiing are examples. <A> The ercoupe was an advanced design for its time, but it represented a bunch of compromises and the inability to do a forward slip was one of them. <S> The plane's designer made up for this by choosing the airfoil so the plane would descend steeply enough with power off <S> so the pilot wouldn't have to bleed off altitude if he was high on final, and by making the landing gear stout enough to manage landing while severely crabbed. <S> Another compromise was the omission of flaps; this was to simplify both flight operation and maintenance but required an airfoil that yielded a flap-like descent with power off (as mentioned above) which is why the ercoupe glides like a brick. <A> The first is commonly done by twisting the wing tips up at the trailing edge, reducing their angle of attack relative to the rest of the wing. <S> It could also be achieved with a change of aerofoil section, or turbulators. <S> Both of these cause drag and reduce efficiency, and the second limits your ability to flare for landing. <S> I imagine those were sufficient reasons for designers not to 'stall proof' their designs.
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The usual way to make a plane 'spin proof' is to ensure the centre of the wing (near the fuselage) stalls before the tips, and to move the Centre of Gravity far enough forward that the elevator doesn't have the power to keep the nose up below stall speed.
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What is a circling approach? What is a circling approach and why is it necessary? I know that if a runway is not suitable for an instrument approach, the pilots should execute landing on a runway which has an instrument approach available. <Q> To add to the above points... <S> Circling Approaches are used when the Approach you want to use and the runway you want to use are not aligned with each other. <S> Say for instance, you are arriving to the terminal area from the North. <S> The runway you want to use is from the South (probably due to wind). <S> You want to get down to the ground ASAP. <S> You can get cleared to approach the airport using an IAP with a Southbound Final Approach Course. <S> They will also clear you to circle the field in a certain direction. <S> We will use East in this example. <S> You will then get clearance to land on the Northbound (from the south) runway. <S> A play by play would be to: Follow the full procedure for the IAP with the 180° Final Approach Course. <S> Once you reach your Circling Minimums, maintain you’re altitude, and turn 30° to 60° to your left. <S> Turn back to your 180 <S> ° heading in time to stay no more than 1.3 miles away from the runway surface for Category A aircraft (unless the airport has published alternate circling distances). <S> It would be similar to a (right in this case) downwind leg <S> Parallel the runway to a point where you can make a normal downwind to base turn. <S> Start your descent to landing Land on runway 36 <S> If you never get the runway environment in sight, go missed at the original MAP. <S> If you lose sight of the runway environment at any time during your circling maneuver, immediately circle back over the runway to fly above it on your missed approach course. <S> And go missed. <S> Remember, the safest place in the airport environment is directly above the center of the runway. <S> One thing to be aware of on Circling Approaches is that the Circling Minimums are typically below Traffic Pattern Altitude. <S> You will be flying slower and closer to the ground in the airport environment than you are used to. <S> Caution must be exercised. <S> Also, the Circling Approach does not have to be a complete 180° turn around to land. <S> It could be in any direction. <S> Finally, some approaches only have Circling as an option. <S> This is due to the approach itself not being aligned with the runway. <S> In the example below, the runway is aligned 179° and 359° magnetic. <A> Circling approaches can also be flown on instrument approaches where the pilot opts to land on another runway not aligned with the final approach segment, but which has more favorable wind conditions, obstacle clearance, greater landing distance available, or some other characteristic which makes it more desirable to land on. <A> Even with Sean's edits that last sentence is confusing. <S> Of course it is ideal to land on a runway with an instrument approach, but when the preferred landing runway is NOT served by an instrument approach, the pilot must follow a procedure to get below the clouds and be able to see to land. <S> This can be accomplished by radar vectors to a visual approach, but depending on the ceiling, minumum vectoring altitude, and the published approach minimums it may be advantageous to shoot an approach to a runway not in use, and once the runway is in sight, circle to land by maneuvering to join the final portion of the VFR landing pattern.
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A circling approach is executed on an instrument approach procedure which or where the final approach segment is not aligned directly with the runway of intended landing.
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Does downwash increase or reduce lift generation? I’m wondering about the impact of downwash on lift generation. I've read that, because downwash creates lift according to Newton's third law of motion, increases in downwash due to greater AoA (especially when augmented by devices such as slots and slotted flaps, which use various aerodynamic effects to increase the amount of downwash generated) result in increased lift. But I've also read that ground effect increases lift by decreasing downwash, so I'm confused how this works. Can someone clarify the effect of downwash on the amount of lift generated and tell me whether I've got it right or not? Thanks! <Q> Downwash is behind the wing and is the result of pressure differences between the top and bottom of a wing. <S> Although the energy conservation bookkeeping says the plane goes up and the air goes down, the main driver of lift is pressure differential. <S> True to Bernoulli, the angled bottom wing slows and increases air pressure beneath the wing. <S> This is "bottom lift" that even simple flat plates have. <S> Airfoils also deflect air upwards and away from the top of the air foil, creating additional lift above the wing. <S> Downwash is created by the movement of air from higher to lower pressure as the wing goes by, filling the void where the wing was . <S> This constant process is known as circulation. <S> Ground effect may not be directly related to downwash, but may be indirectly, as the ground and the downwash stream may create enough of a "fence" to slightly raise the pressure under the wing. <S> A Cessna 172 has a wing area of <S> $174 feet^2$ . <S> $174 feet^2 × 144 inches^2 <S> /foot^2= <S> 25056 inches^2 <S> $ A pressure increase of 0.01 psi from ground effect adds 250 extra pounds of lift! <S> Ground effect is also said to be caused by the wing tip vortices being disrupted by their proximity to earth. <A> This is a most excellent question. <S> I've struggled with this for a while. <S> From a Newtonian perspective, there must be momentum transfer from the flow to the wing in order for the wing to gain lift, which necessitates in the generation of downward airflow. <S> Let's call this downward airflow downwash . <S> However, from the circulation theory of lift, which holds incredibly well for low Mach aircraft, downwash is the source of induced drag (note that this theory does not account for viscous drag or form drag from flow separation). <S> Furthermore, this drag is the result of reduction in lift , due to downwash; increased downwash equals more reduction in lift and more induced drag. <S> Consider the elliptical lift distribution (which for all intents and purposes, can be considered a typical wing distribution for low Mach lift, without loss of generality), <S> the downwash over and behind the wing is constant across the span of wing, and can be expressed as (Ref: Anderson , Fundamentals of Aerodynamics): $$(1) : w=\frac{SC_L <S> V_\infty}{\pi b^2}=\frac{C_L V_\infty}{\pi A}$$ <S> where $w$ is the downwash, $C_L$ <S> is the lift coefficient of the wing, <S> $S$ is wing reference area, $b$ <S> is the wing span, <S> $V_\infty$ <S> is the free-stream airspeed, <S> $A$ is the aspect ratio. <S> Induced drag, for an elliptical distribution, can be expressed as: $$(2) <S> : C_{D_i} = \frac{\pi w^2 A}{V_\infty^2} = <S> \frac{C_L^2}{\pi <S> A}$$ <S> So what do we get from all of this? <S> From equation (2), induced drag is directly proportional to the square of downwash for any aspect ratio. <S> From equation (1), the lift coefficient is proportional to downwash. <S> By increasing aspect ratio, downwash, and therefore induced drag, can be reduced asymptotically to zero, while the wing's lift coefficient stays unchanged. <S> In ground effect, the exact same thing happens as the reaction from the ground makes downwash more efficient at generating lift. <S> This is manifested, once again, from a reduction in actual downwash for a given lift coefficient . <A> Strictly, the more wing lift is created the more the down force on the air. <S> They are equal and opposite forces. <S> Yes, the increased downforce usually results in greater down wash . <S> But if the ground is in the way then the downwash gets spread sideways and its net downward component is reduced. <S> This raises the local pressure between wing and ground, increasing lift. <S> So in normal flight the downwash is a consequence of lift, while in ground effect the added lift is a consequence of downwash.
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In other words, while downwash is necessary for lift, it also results in (induced) drag; increasing the aspect ratio makes downwash more efficient at generating lift and reduces (induced) drag.
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Why do airliners park with the nose facing the terminal? A few other questions have touched on why we don't board airliners from the front and back at the same time. My question is why is it that we choose to board at the front, rather than park the aircraft facing away from the terminal? This question shows that parking backward seems to be unusual. Why is this design not adopted widely? I have two guesses: Is it because of the jet blast? But this can be solved by towing the aircraft away from the terminal before using the jet engines. Because it is difficult to attach the jet bridge without hitting the tail? <Q> To park a passenger plane with its tail towards the terminal has several disadvantages: it would require a pushback tractor (plus personnel) to do that. <S> Thrust reversers in general are not meant for making the plane go backwards. <S> If it was possible for the plane to go autonomously backwards, it would be extremely = too risky. <S> you would also need the pushback tracktor for leaving the gate, you couldn't use engines because of the jetblast hitting the terminal <S> you could not use the APU because it would scorch the terminal the horizontal tail of some planes might have clearance issues with the jet bridge. <S> last but maybe not least: the upper class travelers. <S> They sit at the front for a reason: they get on and off the plane first. <S> Yes, the business and first class could be moved to the back. <S> Now, I don't know if riding closer to the cockpit rather than the arse of the plane has some intrinsic value, but at least it is usually noisier at the back. <S> So customer satisfaction might take a hit there. <S> So: twice the hassle with pushback + other issues, with no benefits whatsoever. <A> I worked at an airport for 3 years. <S> We're under a very strict time table when an airplane lands. <S> An aircraft arriving and departing is called a "turn" and our turn time is roughly 15-30 minutes depending on type of aircraft. <S> Every moment counts. <S> Even a 1 minute delay will get people from corporate screaming at my manager for answers. <S> My manager in turn, would then scream at us. <S> Parking an aircraft <S> so it's tail faced the building would be a massive increase to our turn time. <S> It would take a lot more trouble to take a push back up to the awaiting aircraft, hook it up, tow it back into position, then wait for engines to shut down and APU/Ground Power to come on, than it is to just have it roll up nose first and push back after loading it. <S> Furthermore, the jetbridge would have to manuever around the wings of the aircraft to get to the door, most bridges are too short for that <S> so it's unfeasable, unless they rebuilt like ALL the jetbridges or used a staircase truck (which eats at turn time.) <S> The big one is safety. <S> The engines would be pointing their jetblast where the ramp agents come out of the building to do their work. <S> On most turns, the engines turn off and the APU or Ground Power is used. <S> But sometimes the APU is dead or some maintenance requires running engines. <S> We can't do that at the gate if the airplane is facing the building ass-first and finding a safe place to do such a thing may be incredibly difficult and inconveinent, or they can simply park at the gate nose first. <A> There are certainly airports where aircraft do face away from the terminal. <S> One example is London City, where aircraft use their own power to turn themselves round upon arrival. <S> Also, low cost airlines might do this to speed up turn around time - I've seen Easyjet aircraft turn themselves round at Tenerife, although I can't remember if they did this on arrival or departure. <S> To resolve the issue of jetblast and the terminal in these cases, there is an additional concrete barrier between the aircraft parking and the terminal. <S> This works where the passengers walk (or get a bus) to the aircraft. <S> As has been mentioned, this does not work where airlines use a airbridge, nor for full service airlines who generally like to use an airbridge, in which case the airbridge(s) have to link to doors on the terminal side of the wings.
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Low cost airlines are also more likely to use both front and back doors to speed up disembarking and embarking of the aircraft.
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Has any accident been prevented by bending or breaking the rules? I wonder if there is an incident that pilots saved the plane or minimized the damage by bending or breaking the rules like Sully? (As it's known Sullenberger started the APU at first which was the 15th thing in QRH.) Thanks in advance. <Q> First I have to admit that I have no idea <S> what FAA regulations said about passengers taking part in controlling an airplane in 1989, but I guess it was at least frowned upon, even if the passenger happened to be a pilot. <S> The United Airlines flight 232 made a stunningly successful "landing" at Sioux City airport, much due to the fact that they took an extra crew member from the cabin to control the throttles of their severely disabled aircraft. <S> Unfortunately 112 people lost their lives as the plane cartwheeled after a very rough touchdown, and one might ask what is so successful about that... well: 184 people survived a situation that was in subsequent simulations deemed to be impossible to manage. <S> The throttle operator was a UA training check airman Dennis Edward Fitch, riding as a passenger on this ill-fated flight. <S> It has been stated in many sources again and again, that without his presence in the cockpit, the outcome would have been much worse, even the worst possible. <S> It just so happened, that Fitch had been practicing a similar scenario in a simulator after a fatal crash of Japan Airlines flight 123 in 1985. <S> The reason of that crash was total loss of hydraulics, Fitch wanted to find out if an airliner could be controlled with throttles only. <S> Luckily, it was somewhat possible. <A> 91.3 Responsibility and authority of the pilot in command. <S> (a) <S> The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft. <S> (b) <S> In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency. <S> (c) <S> Each pilot in command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator. <A> As pointed out above pilots may deviate from any regulation in the event of an emergency per §91.3(b). <S> The OP brings up the case of Cactus 1549. <S> But what Sully and Stiles did in powering up the APU first wasn’t a violation of the rules per se, though I’m sure there are plenty of odious airline sim check pilots that cut themselves on their overstarched undershirts who would disagree with this. <S> This even brings up an interesting discussion I once had with a flight instructor examiner <S> I knew who had been a Air Safety adviser to Korean Airlines. <S> He told me he once conducted a systems discussion with a group of KAL 747 pilots in regards to understanding their systems in an emergency. <S> The KAL pilot corps at the time apparently handled their pilots in a very regimented and militaristic fashion. <S> When the chief pilot walked in, they all jumped to their feet and stood at attention, etc. <S> So this examiner guy walks up to the front of the group of the group and asks them: “Ok, so what is the emergency procedure for an engine fire on a 747-400?” <S> The entire group barks out the QRH entry for this contingency at the top of their lungs perfectly and in unison. <S> “Okay.......so what two things do you do in the event of an engine fire if you only have time to do two things?” <S> Dead silence. <S> The entire room stares blankly back at him like a second grader at a spelling bee asked to spell ‘photosynthesis’. <S> OEM approved procedures, standardized general operating practices and legal regulations for aviation are great guideline for safe and reliable operations but they can’t always cover every contingency perfectly. <S> A fundamental knowledge of your aircraft and it’s <S> systems from a correlation level can come in real handy sometimes if you encounter something serious that’s not been documented. <S> It’s something test pilots know all too well, as it can allow them to make very judicious choices on flight test plans and handle unforeseen problems once in the air. <A> In 2017 an MD-83 aborted takeoff above V1. <S> The pilot was widely criticized for that, which was against a lot of rules and conventional wisdom. <S> The NTSB report determined that aborting above V1 was the most correct thing to do in this case. <S> https://www.planeandpilotmag.com/article/ntsb-report-how-this-pilot-saved-116-lives/#.XkzGlopOmhA <A> There have been cases with incorrectly wired controls , with the aircraft doing the opposite action than such a wrongly wired control commands. <S> Then the narrow rules about how to use the control to achieve intended action must be completely reversed, moving the stick in the opposite direction. <S> Doing <S> so does not break the wider rules that cover such malfunctions. <S> But I imagine how difficult is to realize them happening at the first place. <S> This is the main reason I would never like to have just a robot in the cockpit. <A> I will note that in maritime law there is the General Prudential Rule which states that avoiding a collision takes precedence over strict adherence to other rules and regulations. <S> I would have to believe that there are similar provisions in aviation rules.
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One of the more common events is a civilian aircraft making an emergency diversion and landing at a nearby military airbase, such as this 777 flight which diverted to Erickson AB, Shemaya, AK . The rules say to do whatever necessary to ensure safety of flight.
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Can a pilot initiate an enroute descent to an IAF without ATC 's approval? An IFR flight is cleared DIRECT to a published IAF for an approach at the destination airport. The cruising altitude is 10,000’, the IAF crossing altitude is 2,000’ and the T/D begins about 24nm prior to the IAF with standard rate of descent. Since route has been previously cleared to that IAF waypoint, can the pilot commence his descent upon reaching the T/D, or wait to hear from controller or request descent instructions just prior to the T/D? <Q> You are never allowed to simply vacate an assigned IFR altitude without clearance. <S> When you were cleared to the IAF your clearance should have included "pilot's discretion down to ..." of "cross IAF at or above..." or similar words. <S> If you don't get this, just ask. <S> Never presume that you can just start down on your own though. <A> But yes , you can descend down to your Approach without further clearance given you meet a few parameters First, make sure you are cleared for the Approach itself and not just cleared direct to the waypoint. <S> Your assigned altitude is mandatory until you are established on your cleared Approach. <S> Established means that you are on or immediately about to be on (less than a mile of) a published leg of the Approach. <S> Once you are established on your published leg, you can descend to the at or above altitude published for the route. <S> If the altitude has a line above and below it, you must be exactly at the published altitude. <S> If that is the case, you will be verbally stepped down to the altitude by ATC. <S> If the IAP includes a published Terminal Arrival Area, and you are cleared for he Approach, you are considered established on the approach when you are inside of the TAA’s lateral boundaries. <S> The altitudes published for the TAA will dictate your altitude limits you have to remain above. <S> If ATC does not expect you to follow the IAP exactly to include its published altitudes, they will not clear you for the Approach. <S> They will continue to vector you and give you altitudes. <A> The clearance given in the OP allows you to proceed direct to the IAF waypoint, but it does not clear the pilot to deviate from the currently assigned altitude, nor does it clear the pilot to fly the approach. <S> These would require separate ATC clearances. <S> The route at your assigned altitude has been cleared to you - you do have that block of airspace - but not the airspace above or below it. <S> Think in 3 dimensions. <S> Now you may inquire about starting a descent at that point with ATC, but would need a specific clearance to do so.
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No, you can not descend from your assigned altitude until specifically cleared by ATC to descend.
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RATO used to get civilian aircraft out of airports with inadequate runway length? There are plenty of stories of large aircraft accidentally, or emergently, landing at airports that don't meet the plane's runway length requirements. The only solution to getting them out that I've read is stripping them to the point that some authority deems them light enough for takeoff on the short runway. What I haven't read of are the use of any measures to increase the thrust available for the takeoff run. The first idea that came to mind was the use of RATO . Is this possible with civilian aircraft? Is it done? If not, why not? (My second thought was to temporarily install water injection . But then I figured that by the time a system like that could be tested and approved the plane could have been disassembled for overland shipping.) <Q> The Fairchild SA226 had a RATO bottle in the tail to improve single engine performance. <S> As I recall, removing the spades on the main landing gear eliminated enough drag to render the RATO unnecessary. <S> Boeing built twelve "727-200/JATO" variants for use by Mexicana Airlines . <S> The rocket installation was intended for emergency use only when flying out of a hot and high airport at maximum gross weight. <S> Without the JATO, the aircraft would have to be payload restricted to account for the need to reach a safe altitude in the event of an engine loss after committing to takeoff. <S> By having the JATO provision, Mexicana could operate its 727-200s at full payload. <S> In the event of a loss of engine at past V1, the JATO unit would fire and allow the heavily-laden jet to reach a safe altitude and get aerodynamically cleaned up. <S> This old video shows a demonstration of that scenario with one of those special 727-200s: <S> The JATO provision was eventually made obsolete by later developments in the JT8D engine that featured "APR" automatic power reserve. <S> It sensed a power decrease from one of the engines failing on takeoff and automatically boosted the power to the remaining two engines by a significant margin. <A> The same reason you give for water injection would apply to RATO. <S> The airframes are not structurally reinforced, nor are there any mounting points or wiring and switches needed for igniting them. <S> It would be a major endeavor to test and certify such a system for the rare occasions when someone might want to have that option. <A> The difficulty of engineering a RATO is only half the reason, the rest is that reducing weight is really effective. <S> Typically the empty weight of an airliner is about half the max take off weight. <S> That means that it can accelerate twice as fast, only requiring half the distance to reach the same speed. <S> Also, a lighter plane can take off at lower speeds (although not half, as lift depends on speed squared). <S> Put the two together, and wait for the coldest part of the day when the air is densest and it could manage with about a third of the normal runway. <A> RATO capability must be designed into the airframe to a certain extent, you need either built-in structural reinforcement and thermal protection or the ability to retro-fit it later. <S> Built-in capability adds weight that airplanes would be lugging around, retro-fit capability costs money to design in, test, certify, maintain and train pilots to use it. <S> All this would add up to significant extra costs for what is best described as a very infrequent edge case. <S> It's cheaper to very occasionally break up an airframe.
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The DH Comet was equipped with RATO.
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Why does the UH-1 Huey have a hump at the rear of the cabin? Why does the Huey have this weird hump as shown in the picture? For some system? Why not remove it? https://www.helis.com/h2/uh-1h_seats.jpg <Q> A copy of the original image can be found here , which is about 5 'pagedowns' down this page , which has a number of other excellent Huey-model photos. <S> Fwd/aft, left <S> /right, up/down. <S> The rotor provides the lifting forces and driving forces and these are quite concentrated around the rotor axis. <S> Picture the airframe like an empty beer can - some panels are required to cope with the forces while remaining in shape. <A> It's where the main rotor transmission and control servos are housed. <S> The forward bulkhead of the "hump" WAS the entire aft cabin bulkhead of the original Huey models. <S> Starting with the D model (I Think) <S> the cabin was extended around the transmission tunnel to form what are called the right and left alcoves. <S> The original shorter body Hueys were adapted to the gunship roles. <A> Click to view, cropped from https://forums.eagle.ru/showthread.php?t=98895 <S> The biggest feature in that area is the fuel tank, which is roughly 0.65 m $^3$ (165 US gal). <S> With a cabin height of 1.2 m (it's not a standing cabin), the base (assuming square) would be 0.74 x 0.74 m (2'5" <S> x 2'5") of floor area, which does look right.
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It's a bit of structure to guide the rotor forces into the rest of the airframe, it would not be good if this bit went missing.
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Do aircraft have accelerometers? Do modern aircraft employ accelerometers or other similar equipment to measure g-forces on the aircraft? I could imagine this being used as an inspection/service indicator, particularly after hard landings. Or do hard landings and other forceful flight regimes typically not pose any significant structural concerns? Update. Related on determining hard landing inspections: From Aero Magazine on Boeing conditional inspections Section on AMM changes: Boeing is modifying the 737 AMM, section 05-51, and will revise the AMMs for other Boeing-designed airplane models, to include these vertical acceleration values (table 1). For Douglas-designed airplanes, similar values are being generated and will be available in the AMMs in early 2001. The values are intended as thresholds that can be used to help determine whether a hard landing inspection is necessary. If the flight crew concludes that it has experienced a hard landing, the AMM conditional inspections should be performed even if the acceleration readings do not exceed the values added to the AMM. The vertical acceleration values are to be used by operators, in addition to or in lieu of flight crew judgment, to initiate conditional maintenance inspections. Source: Aero Magazine <Q> Most modern aircraft, which includes long range airliners since around 1970, all airliners since not much later, and basically anything with glass cockpit, do have very accurate accelerometers for all three axis, as part of the inertial reference system . <S> They are important instruments for the autopilot, as they provide faster feedback on the effect of control deflections than the air-data references, and essential for navigation as cross-reference for detecting GPS errors and the inertial navigation serves as a backup for GPS (and served as primary navigation over the oceans before wide GPS availability). <S> Airbus (since A320) even defines the pitch command by vertical acceleration in the normal law. <S> And yes, they are also used for detecting hard landings and their severity. <S> The pilot never sees the direct accelerometer output except in fighter and aerobatic aircraft though (well, almost never; there are a couple of other cases). <A> I think you need to define "modern" aircraft, the question is pretty broad as-is. <S> And even interpretation of what you mean could vary. <S> i.e. are you referring to a real time dial showing actual Gs in the cockpit? <S> As quiet flyer noted, as a reference instrument an accelerometer is very important for aerobatic flight. <S> Most small modern general aviation aircraft don't have them though. <A> When I worked in the industry in the early 2000s, Eurofighters had g-sensors recording during flight, and put you into a different engine service regime above a certain limit. <S> There was a matching detent on the stick (not sure if virtual or physical) that warned pilots if they were going to go over the limit. <S> Twenty years on, given the cheapness of modern mems sensors, I'd find it unlikely that any large aircraft engine lacked any accelerometers, though in most cases they are more likely to be used to monitor vibration or fatigue life than g load. <S> A quick search finds many suppliers, e.g. Meggitt , who list the following uses, but not specific engines or airframes they are used on: Our piezo-electric accelerometers are ideally suited to a wide range of jet engine (civil and military), helicopter and space applications: gas turbine engine monitoring airframe structure vibration analysis gearbox analysis bearing analysis [etc] <A> Of course they do. <S> You can find them in just about any cockpit from the modern aircraft of today down to about the 1930's. <S> Here's an example. <A> Depends on the aircraft in question. <S> Airplanes used for aerobatics or military fighters will commonly carry them as a reference for pilots on just how hard they’re loading the airplane at any one time, though many good aerobatic pilots have enough time that they can kinesthetically sense just how hard they’re loading the airplane. <S> Hard landings are gauged kinesthetically and by the vertical speed at touchdown. <S> Exceed certain metrics and the airplane will be inspected by protocol. <A> It has been answered for big aircraft, so just as a sidenote: Multicopters ("drones") have accelerometers (and other sensors) as integral part of their flight computer. <S> Without it they would drop from the sky pretty quickly.
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However, while a real time instrument is not needed for a larger air carrier, accelerometers feeding data to a flight data recorder for mishap investigation and recording of life cycle data for airframe fatigue calculations is important. Transport category aircraft don’t carry G meters as it’s not very useful to their flight profiles.
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Can Flex thrust be lower than climb thrust? Let's restrict this question to airliners with 2 jet engines. For the remaining of the question, I'll use the term flex to designate reduced take off thrust as I'm more familiar with airbus's systems. Flex will be the thrust selected when thrust levers are in the flex detent and climb thrust the one selected when lever are on the "climb" detent without autothrottle engaged. I assume other manufacturers have an equivalent way to easily select those values. Both flex and climb thrust are lower than TOGA thrust. In good condition (long runway, good weather, almost empty aircraft,...), how low can flex thrust be? Can it be lower than climb thrust? In this case, what is the rational for accelerating from flex to climb thrust given flex is made to increase engine lifespan by reducing thrust? <Q> Yes. <S> On the CF-34 family, in theory, a maxed-out flex setting can be in the mid 80s N1 whereas climb thrust is normally high 80s/low 90s, and you could see thrust rise when setting climb if an extreme flex setup (max Assumed Temperature) (or in the case of the non-fadec engines like the 3B1, the climb bug appears at a higher value than the flex take-off thrust bug when you select "climb" thrust in the FMS) <S> The reason is to do with what you might call the mission priority of the two settings, and where the actual benefit in flex lies. <S> With flex, the priority is distance and gradient for obstacle clearance. <S> The benefit of using the lowest setting is only partly from lower temperatures; an even bigger factor is erosion from silica particles (outdoor dust) which is most severe below 1000 ft. <S> The dustier the environment, the larger the flex benefit. <S> (In the Middle East, CRJ operators were wearing out engines after only 5-7000 hours because they were doing <S> max thrust takeoffs all the time and had to be cajoled into using flex.) <S> Climb thrust has a time priority, from an operational balance-of-factors perspective. <S> You want to get to altitude in an optimized time-related profile (as soon as possible taking various things into account), and an optimized time-related profile can require more thrust than the minimum required to meet take-off performance, in cases where a very large flex allowance is available allowing minimal take-off thrust. <S> Setting climb thrust that is a little higher than the flex take-off setting has little negative impact on engine life because you are now high enough that the erosion impact is negligible <S> so there's little engine life benefit to a slower climb to altitude <S> and you might as well optimize climb thrust to get there faster. <A> Can Flex thrust be lower than climb thrust? <S> For Airbus, <S> no, <S> it cannot. <S> Because as you've noted, there's no rationale for it. <A> Flex allows there to be various settings for Takeoff power. <S> Climb thrust is less than Takeoff power <S> (Takeoff is usually time-limited whereas Climb is not), but there can be several settings for Climb thrust to ensure that today's Climb is less than today's Takeoff. <S> Boeings use Climb, Climb1 (-10%) and Climb2 (-20%) and <S> the FMC picks the suitable Climb power to go with today's Takeoff power. <S> So a full derate will end up with Climb2, whereas a partial derate may need allow Climb1.
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The flex setting is the lowest setting that meets the takeoff and initial departure performance requirement for accelerate/stop and initial climb gradient for that runway and all up weight.
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How likely is it that there is someone knowledgeable about piloting in a flight control room? I saw a reasonably looking video about a non-pilot trying to land a plane with the help of a flight control tower (in a simulator): (it is in French). I believe that this was an ideal case where the plane was compatible with the airport so that the landing was almost automatic (they showed a short version of (successfully) trying to land without the automatic mode). The person in the control tower was extremely knowledgeable about the plane, explaining exactly where to press, where to look etc. Assuming that the whole exercise was realistic - how likely is it that there would be someone handy who could, by heart, explain via the radio what the exact steps to take are? Note: I realize that the situation will be different between a large airport (where they could make an announcement " we are looking for a Boeing 747 pilot, please contact the reception desk if you are one ") and smaller ones. In the video, they started from a cruising altitude and it took minutes to go from "there is nobody in the cockpit" to "listen to me carefully, I will guide you". It is more the realism of time which I am trying to assess. <Q> The answer depends a lot on the type of plane being flow. <S> They may be able to offer very generic advice such as "See the handle that is shaped like a wheel? <S> Push it down and that will lower the landing gear. <S> " <S> For simpler GA aircraft they might offer some basic assistance on how to control the aircraft, slow down, deploy flaps, etc. <S> but there is a lot of muscle memory and technique honed by hours of practice needed to perform a "good" landing. <S> Just explaining the exact steps to take over the radio isn't going to be enough, there is a lot more to it. <S> Think about the first time you drove a car with a manual transmission: <S> Did the person telling you to push in the clutch, shift gears, then let it out smoothly while adding gas help you to do it smoothly, without stalling the engine, jerking, or racing the engine? <S> Probably not! <S> About the best they could probably hope for is to help the non-pilot maneuver into a safe airspeed envelope to survive a controlled crash landing at the airfield where emergency services will be on hand to provide immediate help. <A> If by Flight Control Room <S> you mean Air Traffic Control, not very likely. <S> Simulators are operated by flight instructors. <S> They will role play ATC for the “pilot” being instructed. <S> So of course, they know the aircraft intimately. <S> There is no requirement for ATC personnel to even have a pilot certificate. <S> If they do have a pilot certificate, they will not be type rated in that particular aircraft. <S> They may be able to help with a GA aircraft. <S> For a commercial aircraft, they will reach out to a non-ATC pilot of one of the airlines whether that pilot is in the airport terminal, pilot lounge, or even in the air. <S> More likely, they will patch the cockpit into the maintenance and training departments of the particular airline that owns the plane in danger. <A> In this case , the passenger landed a two-seater with the help of flying instructors based at the airport. <S> During this incident , ATC phoned a type-rated pilot and relayed instructions. <S> The passenger did have 150 hours on spamcans but hadn't flown for years and never a turboprop <S> When her husband collapsed , the wife of a pilot was talked down by another pilot in a similar aircraft while they were both in the air. <S> Again, she didn't have a licence <S> but she had solo-ed
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While plenty of air traffic controllers are also pilots on the side, it is highly unlikely that anyone on duty at the time would happen to have a type rating in a large complex turbine aircraft, and/or enough knowledge to talk through checklists.
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What is physics explanation for minimum sink rate airspeed? I did some research on Minimum Sink Rate, and saw much information defining it, (such as it is the speed at which the aircraft will remain in the air for the longest time, etc.) and how it is generally lower than Best Glide speed, and is generally a few knots above stall speed. There was also some information about what is used for (when you are trying to remain airborne for as long as possible after engine failure in order to deal with an emergency, or for gliders to maximize the climb effect from a thermal), …. But I could not find, anywhere, an analysis/explanation for how this works, from a Physics perspective, as you can easily find to explain Vx, (best angle of Climb airspeed), and Vy (best rate of climb airspeed), that explain/analyze them from a Physics perspective (Vx is speed at which you have the highest Excess Thrust , whereas Vy is the speed at which you have Maximum Excess Power ). Also, from my limited understanding, what I did read seems to violate my basic understanding of what Min Sink Rate means, from a Physics Perspective. As I would understand it, Min Sink Rate Speed is the speed at which your rate of descent is the lowest, (you will remain airborne for the greatest amount of time). This is equivalent to the airspeed at which the aircraft is losing altitude, (Potential Energy), at the slowest possible rate. With no power on the aircraft, loss of energy (altitude) is directly related to total drag, (energy must be conserved!), and this occurs at L/Dmax. All the complexities involved with determining Maximum Excess Power, or Maximum Excess Thrust, as are required to analyze Vx and Vy, become moot. So although it appears to be accepted wisdom that Minimum sink is different from Best Glide, this seems to violate basic physics. They should both occur at the airspeed (AOA actually) where total Drag is minimized, i.e., at L/Dmax. Where am I going wrong? <Q> From first principle, assuming the airplane is a point mass, no wind, small angle of attack, and thrust acts in-line with drag: $$T-D-W\sin \gamma=m\dot{V}$$ <S> where <S> $T$ is thrust, $D$ is drag, <S> $\gamma$ is angle of climb, <S> $m$ is mass of the airplane, <S> $W=mg$ <S> is weight, <S> $V$ is airspeed/forward speed (assuming no wind). <S> In a total power off scenario, $T=0$ , and assuming steady-state, $\dot{V}=0$ : <S> $$\sin \gamma = <S> -\frac{D}{W}$$ <S> The rate of climb ( $\dot{z}$ ), which is the negative of sink rate, is related to angle of climb by: $\dot{z}=V\sin \gamma$ . <S> Therefore, we have: $$\dot{z}=-\frac{DV}{W}=-\frac{P_R}{W}$$ <S> Therefore, for minimum rate of descent, we would like the minimum power required ( $P_R$ ). <S> Note: <S> for minimum glide slope, it corresponds to <S> $L/D_{max}$ <S> , but not for minimum rate of descent. <A> You are right that in order to achieve minimum sink rate, you need to minimize energy losses. <S> And yes, energy losses are related to the drag. <S> But here you need to stop and think again what 'related' exactly means. <S> The drag is a force, not an energy. <S> But when you multiply the force acting on moving body by its speed, you get power (that is energy per unit of time) inflicted by this force. <S> (Actually, you have to multiply only the fraction of force, which is parallel with the velocity vector, but drag is, by definition, acting directly against movement, so this is fulfilled automatically). <S> Therefore energy losses are drag multiplied by speed. <S> At L/Dmax you are flying with minimal drag force acting on the airplane (for steady flight), but energy "consumption" is not at the minimum. <S> If you decrease airspeed a bit, drag force increases by some small amount, but the product of airspeed and drag decreases thanks to decreased speed. <S> So you keep slowing down until these two effects cancels out and you end up at the point with minimal energy loss rate. <S> That is the least "Watts" of drag, not "Newtons". <A> I would leave out Vx and Vy for now, as they involve engine/prop efficiencies. <S> In gliding, a plane "burns" altitude to produce the forward movement necessary to use the far more efficient wing to produce lift. <S> Were it not for wing lift, minimum sink rate would be strictly a function of drag, as it is with an old style hemispherical parachute. <S> This combination of airspeed and AOA burns the least amount of altitude "fuel" per unit of time. <S> Vbg is generally a bit faster because glide distance , not time in the air is the determining factor. <S> So, we pitch down for a slightly higher airspeed, "burning" our altitude faster. <S> But tilting the larger lift vector further forward achieves greater gliding distance in spite of a higher rate of vertical descent. <S> Notice in the lift equation: <S> $Lift = <S> 1/2 <S> × Coefficient × Density × <S> V^2 × Area$ <S> the effect on lift of changing AOA is linear, whereas changing V is squared. <S> So, in speeding up (pitching down) to Vbg, you drop faster,but get "pulled" forward to a greater degree. <S> Physics is not always intuitive or logical. <S> Like fathoming the sides of a vector triangle, it can be simply amazing.
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At minimum sink rate airspeed, the lift to drag ratio is at its maximum.
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How many fastener can an aircraft lose? I see this GIF animation a few times then I wonder how many fastener can an aircraft lose before it becomes dangerous. I’m sure losing one wouldn’t be an issue due to safety margin built into every component of aircraft. But how many fastener? Original link https://www.gifng.com/wtf/65633/ <Q> Pressurized aircraft create a whole new set of issues. <S> In some cases you can lose a whole bunch of them and even lose a full panel without issue as was the case on Delta 2412. <S> While in other cases single bolts or fasteners are far more critical. <S> Fasteners on stationary parts wont create the same imbalance issues as say, losing a fastener from a prop spinner or the such. <S> Fasteners coming loose and being ingested into engines or other critical components can be an issue which is similar to the issue with the Concorde incident . <A> It depends on aircraft type. <S> Normally missed permanent fasteners are not allowed when found. <S> But in some areas it is allowed to operate A/C with limited quantity of missing fasteners for limited time period (for example belly fairings on T7). <A> Many might not like my answer, but from my perspective, its as follows. <S> Even if the aircraft loses all these wing fasteners, nothing will happen to the aircraft. <S> Unless the loose panels or nuts find their way into the engine/Jet. <S> The wings are welded and form the primary structure of the aircraft, like a skeleton. <S> These panels cover the Fuel tanks, Anti Freeze systems, Wiring, Mechanicals to the ailerons, mechanical cables, rods, radar and other systems installed in the wings. <S> In addition, these panels aid in drag reduction, which helps with fuel efficiency. <S> If an aircraft loses any of such panels in flight, it just increases the drag and causes minor imbalance, when the crew need to act and reduce the speed accordingly to ensure no additional damage is caused to the internal materials. <S> In most commercial aeroplanes, it mightn't cause drag too, because the wings shape is designed in such a way, there is no pressure on the wing from the top. <S> The front end of the wing will be thicker and the thickness tapers down by the edge, where the wing meets the flaps.
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There is no straight answer as it depends on the individual fastener and specific aircraft in question.
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Can a private jet take off without notifying anybody and land on private land in another country? If you have a friend in the USA who owns a lot of land that is suitable for landing a plane, and you own a private jet with 2 pilots in Norway, can you take off in private property without notifying anybody on what you have on the plane and where you are going or anything like that and fly to the USA and land on the property of your friend? Is that legal to do? <Q> No, you would need to arrange for customs as you are crossing an international border. <A> Yes, it is possible to land an airplane in the US at a private airport when you have taken off from a foreign airport. <S> Doing this is a federal crime. <S> Since you are smuggling something, you may not care about the legality. <S> When you are eventually caught, you will go to prison. <S> Your assets will be confiscated by and forfeited to the government. <S> And once you are released from prison, you will be deported and blacklisted from entering the US ever again. <S> Your gold will not be returned to you. <S> It is not worth the risk. <S> Especially when the gold is worthless unless you can convert it to money. <S> You can’t do that legally either (more prison time). <S> Even money gotten through illegal means is forfeited to the government. <S> You have to declare any goods or monetary instruments (even gold) <S> you are transporting to Customs and Border Protection located at the AOE. <S> There are trade laws, aviation laws, customs laws, banking laws, tax laws, Anti-terrorist laws, etc. <S> that you will be violating if you do not. <A> In general*, any time people or cargo enter another country, they must do so at a designated Port of Entry, i.e. where customs and immigration officers are stationed. <S> This is true regardless of whether traveling by land, sea or air. <S> Trying to enter other than at a PoE is usually a serious crime , and in the case of flying without a proper flight plan, may even get you shot down . <S> In the US specifically, you can request (for a fee) that these officers meet your flight at an airport other than a designated PoE, which is a really convenient perk for GA pilots. <S> As far as I know, they will only agree to do this at public airports, and if you ask about a private airport such as your friend's farm, they'll tell you to land at a public airport first to legally enter the country and then continue to the private one as a domestic flight. <S> (* Open border agreements like Schengen are an obvious exception.) <A> Think about how your question is fundamentally different from this one: <S> If you have friend in the USA that owns a lot of land that is suitable for landing a plane, and you own a private jet with 2 pilots in Colombia , can you takeoff in private property without notifying anybody on what you have on the plane and where you are going or anything like that and fly to USA and land on the property of your friend? <S> Is that legal to do? <S> But would anybody notice that I'm transferring cocaine if the cocaine is hidden <S> and I put the cocaine there long before the actual travel. <S> And would I need to arrange customs to come to me? <S> And how would I do that. <S> This is just me wondering if this is actually possible. <S> I'll bet you can answer this question all by yourself without even consulting additional sources. <S> If not, you can probably put on your Customs and Border Patrol hat and ask yourself: "What would I think of a covert flight of this nature crossing into my airspace? <S> It's probably a totally cool, totally legal flight with no contraband on board. <S> I'm gonna go ahead and do nothing." <A> No, your plan could never succeed. <S> You could not file a legal flight plan since your plan has no provision for landing at an appropriate port of entry for customs and immigration clearance. <S> If you attempt to make the flight without filing a flight plan, you would necessarily need to transit the North American ADIZ (Air Defense Identification Zone) . <S> The map below does not show the Alaska zone, but rest assured it also exists - there is no way to cross into the north american land mass without being detected. <S> Any aircraft flying in these zones without authorization may be identified as a threat and treated as an enemy aircraft, potentially leading to interception by fighter aircraft. <S> With no defensible justification for your presence in that airspace you would be treated as a hostile aircraft and dealt with as such. <S> Image Credit. <A> I'm certain there will be problems with this, because this is very much the way smugglers move goods across a border without letting customs authorities inspect it. <S> If you cross from international airspace to American, without a flight plan, at the very least you'll be directed to land at a recognized airport for customs, and if you don't respond to attempts at contact, it's possible warplanes might be dispatched to intercept you -- this <S> could even go as far as a shoot-down, in the worst case. <S> Even if you "aren't smuggling," if you have anything of value on board, this kind of flight is smuggling. <S> It will also run afoul of immigration laws, if anyone on board isn't an American citizen (and will be seen as suspicious in that regard even they are).
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No matter from where you takeoff, nor in what country your aircraft is registered, if you cross the US Air Defense Identification Zone, you have to land at an Airport of Entry before proceeding elsewhere. No, you may not do it legally.
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Did people really hand-start big bombers in WWII? I am not a pilot so I don't know anything about hand starting propeller aircraft. But I wonder how easily can the propeller fire up unexpectedly during the procedure even if it's done right. Whenever I see an old WWII movie and the guys are turning those big props on the bombers, I always think of that question. <Q> When you shut down a radial the unscavenged oil in the case (oil coating the surfaces that didn't get pumped back to the reservoir tank) runs down and seeps past the rings of the cylinders directly below and to each side at the bottom. <S> In theory, it can create an hydraulic lock if there is enough oil collected in a cylinder, that happens to be on its compression stroke (both valves closed), and the oil volume is more than the cylinder volume at top dead centre. <S> Although an actual hydraulic lock is fairly rare (it takes quite a lot of oil), you still have to check for it because if a jug fires on start while one of the bottom cylinders is locked, it'll bend that jug's connecting rod and/or crack the head. <S> The engine has to be turned with no ignition/fuel to test for this. <S> Typically it's done by hand as shown in those films. <S> If you feel a hydraulic lock coming on as you pull through, you turn the engine the other way to back it off and can remove the lower plugs to let the oil drain out. <S> An aircraft could have propellers that are out of reach of the ground, or there may be some other reason, so you also have the option of doing it with the starter with fuel and ignition turned off. <S> There is always some oil collected and <S> when the engine is cranked it goes out the exhaust valve when it opens and coats the inside of the exhaust ducting. <S> The coating of oil takes quite a while to burn off the inside of the exhaust manifold, which is why they belch smoke for 30 seconds to minute after they start. <S> It IS possible to "hand start" a big radial in a fix, using things like tires slipped over the prop and pulled by a car with a rope, but not by hand unless it's a smaller radial, <S> say under 1000 cubic inches. <A> The procedure you seem to refer to isn't hand starting. <S> It's done on radial engines, with ignition off and valves locked open, to clear oil that may have settled in the lower cylinders (by seeping past the piston rings while the engine was standing) and prevent a hydraulic lock that could bend a piston rod or otherwise break things (at the absolute minimum, foul spark plugs) in the engine if cranked under power without this precaution. <S> Unless there's something very deeply wrong, the engine can't start with the ignition off. <S> Engines of the size you'll have seen this done for, however, are never hand started. <S> Either ground starting carts were used to supply battery power for electric starters, or cartridge starters were used to get the engine spinning so the magnetos could fire the spark plugs. <A> It can still be done on small engines today. <S> One of two conditions must be met. <S> Either the ignition must be on. <S> Or, the magnetos are not properly grounded. <S> Turning a prop past its compression point could cause the engine to fire through as many cycles as the available fuel will allow. <S> Even a few degrees of turning through the arc could cause this to happen. <S> One of the two magnetos will normally have an impulse coupling on it to assist in spark generation during very low RPMs. <S> Slowly cycling an accidentally ungrounded magneto can cause a horrific accident. <S> This is why you should shut down the engine by starving the engine of fuel. <S> That way, no fuel is left in the cylinders in case of accidental spark. <S> Also, make sure the mag switch and master switch are off before approaching the front of the aircraft. <S> Lastly, perform a p-lead check just before shut-down. <S> An automotive example of this danger can be found on old diesel trucks with mechanical, engine-driven fuel pumps. <S> If the fuel shutoff was not engaged, the truck could start itself if it were allowed roll a few feet. <S> Even with no one at the controls.
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Hand-propping was only done on small engines, not bombers or even fighters. If there is an hydraulic lock in a cylinder the starter won't be able to do any damage on its own (it'll either bog down or its clutch will slip), so it's safe to do, if done properly.
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Can you fly 2000 miles on an engine that costs less than $500k? If so, what type of engine? Ok so Im exploring ways to bring cargo and medical supplies to various rural cities in say Africa without relying on ground infrastructure. Just short and cheap runways spread around the continent. It seems any type of VTOL plane wouldn't have the range. Electric is also out. It also seems like piston planes don't have the range, while turbojets are millions of dollars. What about used turbojets? Whats stopping piston engines from flying longer? <Q> graphlite rod (pull-truded carbon rod with incredible strength - widely used in sailplane spars) powered by a couple of aviation diesels like the Austro Engine E4 . <S> The Specific Fuel Consumption of the E4 is .336 lbs/hp/hr. <S> Except for similar competing diesels, nothing in any traditional aircraft engine configuration comes close except the old tubro-compound mechanical-monstrosity radials like the R3350 that could get into the high 3s (normal gas piston engines are around .45 lb/hp/hr and turboprops well above that, around .5-.6 lbs/hp/hr). <S> The E4 is 168 <S> Hp so two would give you 336 HP for take off, and the engine burns 5 US Gal per side at 60% cruise, or 30 lbs per side, so to go 2000 nm, <S> if you can get the thing to cruise at 150kt, you need 130 US Gal capacity plus a VFR reserve, say 140 gal total, or 840 lbs of fuel. <S> So design an airframe that can haul, say, a thousand pounds of payload with those two engines and 840 lbs of kerosene, and is clean enough to go 150kt, and there you have it. <A> The reason there are few, if any, in service today is that there is no real market. <S> Jets have taken the long-range commercial market, and pilots of smaller planes generally don't want to go that far without stopping for bathroom breaks. <S> If you are looking to design an unpiloted plane, the problem becomes even easier. <A> This is perhaps not going to be a very good answer to the specific question, but the mission you describe would constitute some out-of-the-box thinking. <S> As John K already suggested, a very light construction, perhaps in the spirit of Rutan Voyager suggested by Jamesqf would be a good starting point. <S> Large wingspan to get efficient wings would give the chance to use less powerfull and/or exotic engines. <S> John K's example of Austros is a good one. <S> In my mind what you should design is a motorglider on steroids. <S> Relatively large cargo would otherwise require a lot of thrust, but you could compensate with wingspan and 2 or even three lifting surfaces. <S> Leaving the pilot out would save at least 400 lbs of weight (pilot, seat, controls, gauges and such), plus you would not need any pressurising, so you could fly ballistic profile flights: high power ascents (but not that steep as exess thrust is not great with full cargo), and the gliding the rest of the way. <S> You could even feather the props and shut down the engine -> <S> no cruise consumption (piston engines typically are not very efficient when operating in partial load = cruise). <S> I don't think speed is of essence here, <S> as even a cruise (or in the case I'm proposing, glide) speed of say, 100 kts would be, knowing the infrastructure there , at least ten times faster. <S> I see one real problem though: landing at destination, automatic or remotely controlled? <S> If rc, how? <S> Satellite would be the only aplicable solution, but might prove troublesome with videostream bandwidth, lag etc. <S> If automatic, oh man the effort of programming relating to all that needs to be taken into account. <S> So: is dropping the cargo by parachute out of the question? <A> The main distance limitation for a plane is weight: every extra pound of fuel means one less pound of payload. <S> Planes can be equipped with "ferry tanks" that increase endurance for long open water legs, but then they're bumping up against (or even over) maximum gross weight with just the pilot (no passengers or cargo). <S> Take the pilot out and you can add more fuel to go even further. <S> Unless your goal is moving the plane itself, though, having no weight left for payload doesn't really allow anything useful to be accomplished. <S> Note that aircraft range is often specified for something like 75% power at cruise. <S> Since drag is proportional to speed squared, flying slower would use a lot less fuel and thus extend your range, which may be fine for a drone that lacks the human need to stop every few hours. <A> 2000 miles with a piston engine has been done more recently - check Wikipedia's entry for the AAI Aerosonde, which crossed the Atlantic (2031 miles) burning only 1.5 US gallons of fuel. <S> It includes a reference to the later "Spirit of Butts' Farm" which did that as well with a total gross weight of 11 pounds / 5 kilograms. <S> Autopilots are far more capable and small than they were then and often include autoland capability. <S> What you want to do can be done.
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It's perfectly possible to build piston-engined planes with ranges of 2000 miles or more, for instance many WWII planes like the B-17 and B-29, pre-jet airliners like the Lockheed Constellation, or the Rutan Voyager. You should be able to use modern, non-certified engines derived from the automotive market, can fly at efficient speeds, and don't have to worry about breaks. Your best bet would be an airplane/drone that is built from carbon composite and
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How often can I fly my own small plane? I was wondering about how often can one fly a privately owned plane? Is it somehow like owning a car where you just light up the ignition and just drive away? Obviously, there are a lot of regulations and rules... but say I have my plane parked in a hangar in a nearby airport. Can I just drive up to that airport and take my plane for a spin anytime I want (after coordinating with the control tower)? <Q> Depending on what country you live in, yes, but it will cost you. <S> It's probably the cheapest to fly an airplane you own in the United States. <S> Here, the answer is yes, with very little restriction, you can just drive out to the airport and fly an aircraft within the National Airspace System. <S> You just must abide by the legal and medical requirements for you, and the legal and operational limitations of the aircraft. <S> Most airports throughout the country are uncontrolled, so you may have limited, if any, interactions with ATC. <S> The ability to fly pretty much anywhere you like with very few restrictions is what makes GA so appealing in the United States. <A> This varies heavily by country, and I know some countries have almost no general or private aviation. <S> But in the UK, USA, Australia, most of Europe etc <S> yes owning a plane is almost like owning a car in terms of freedom to use it. <S> Certainly in the UK, where I'm from, you can take off from a private strip in uncontrolled airspace with no radio and no flight plan. <S> Flying is heavily regulated, but a lot of non-pilots are astonished at how easy it is to fly and how little oversight there is once you have a valid licence and aircraft. <S> Even using a club aircraft is often less onerous than renting a car. <S> say I have my plane parked in a hangar in a nearby airport, can I just drive up to that airport and take my plane for a spin anytime I want (after coordinating with the control tower i guess)? <S> Absolutely - weather and local rules depending, this is exactly how many private pilots operate. <S> At my airport, cooridinating with the tower is as complex as 10 second phone call to <S> tell them <S> you're going flying. <S> Or, you can even do it over the radio though that's discouraged. <A> In the US, you can pretty much legally fly your private plane whenever you want, as long as the ceiling and visibility are compatible with flight under Visual Flight Rules. <S> If you have an instrument rating, then you have even more freedom, but you have to follow certain procedures in order to exercise that freedom. <A> Carlo Felicione is exactly right. <S> His answer is spot on. <S> In the US, you can fly at any time, day or night, as often as you would like. <S> Every day if you want. <S> Just as long as both you and your aircraft meet the minimum legal requirements to fly. <S> An easy memory aid to remember the legal requirements is: Pilot Must be in possession of proper license, medical certificate, and ID. <S> Must also be current on the operation of the aircraft. <S> Illness - free from any affecting flight. <S> Medication - restricted <S> Stress - Be mentally fit to fly. <S> Alcohol - Effectively, none allowed Fatigue - free from any affecting flight. <S> Emotion (hard to legally quantify) Aircraft Documents - E. A.R.R.O.W. <S> C.C.C. Inspections - A.V.1.A.T.E.S., Preflight Maintenance - ADs, 337, MELs, KOELs, TSDS Life Limited Parts <S> Equipment - Primarily 14 CFR Part 91.205 enVironment NOTAMs (for TFRs, NavAid outages, construction, etc) Weather at departure, enroute, destination, and alternates Known ATC delays Runway lengths of intended airports of use Alternatives to your plan (alternate airports or transport) Fuel requirements of flight Takeoff and Landing performance calculations <S> Extenuating Circumstances Flight conditions must be within your Personal Minimums. <S> There are so many airports without control towers that you would not need to coordinate with anyone. <S> An airport with an operating control tower would control their respective airspace. <S> But, working with them is relatively easy. <S> Typically, you only need to notify them of your intent to fly once you have started your aircraft engine and are ready to taxi. <S> They will then give you clearance instructions. <S> If you intend to fly VFR, no flight plan is necessary. <S> Although, one is highly recommended. <S> And, there are a lot more and a lot stricter rules of the sky than there are rules of the road. <S> You can’t legally just jump in your airplane and go for a spin. <S> At least here in the US, that is.
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Just like driving a car, you are free to fly an aircraft whenever, wherever (taking into consideration airspace, restrictions, and safety of flight) and however often you like. If you intend to fly IFR, you will need to file a flight plan at least 30 minutes ahead of time. Unlike a car, there is a lot more planning and prep work that is required to go into each outing.
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Is it possible to use refrigeration technology to cool the skin of supersonic aircraft? The fastest air breathing aircraft, the Blackbird SR71 flew at speeds above Mach 3. Its engines could achieve much higher speeds but were limited by the aircraft's skin which would melt due to friction with the surrounding air should it fly faster. Is it possible to use refrigeration technology to cool down the aircraft's skin so it can reach much higher speeds? <Q> Is it possible to use refrigeration technology to cool down the aircraft's skin so it can reach much higher speeds? <S> Fundamentally: no. <S> Refrigeration technology moves heat energy around, it doesn't get rid of it. <S> Your fridge moves heat from inside to the outside. <S> To get rid of it, you have two means, broadly speaking: <S> Heat up some mass and throw it away <S> Radiate it away as light/IR Air cooling fundamentally heats up the surrounding air, and moves the now hot air away. <S> I believe the SR-71 used it's fuel as heat sink as well, heating the fuel before combusting it, and ultimately throwing it away. <S> Radiating <S> it is inefficient at low temperatures. <S> And it's directly dependent on surface area, which is at a premium on a plane. <S> So in essence you'd have nowhere to put the heat energy you removed from the skin of the aircraft... <A> The SR-71 speed was limited by the maximum allowable temperature of the air entering the first stage compressor at the front of the engine (~800F). <S> The airframe heat load at mach 3 would far exceed the heat transfer capacity of any refrigeration system that could possibly fit inside the plane, and its weight would reduce its useful payload to zero. <S> A better solution might have been to coat the hottest parts of the plane with insulating tiles like those used on the space shuttle, but that technology was unavailable in the late 1950's and early '60's when the design of the SR-71 was developed. <A> As already pointed out in another answer, the SR-71's speed was limited by engine intake heating, its wings were fine. <S> One can add that the main undercarriage tires in particular needed cooling by the fuel on its way to the engine, due to their close proximity to the more heat-resistant wing. <S> Reaction Engines are currently developing the SABRE air-breathing rocket engine, which features a helium-refrigerated "pre-cooler" heat exchanger. <S> This chills the incoming air and is expected to enable speeds up to and beyond Mach 5. <S> The waste heat is used to drive the engine's thermodynamic cycle and pre-heat the hydrogen rocket propellant. <S> It has attracted major funding from several international aerospace bigshots. <S> At the time of writing (early 2020) the pre-cooler has successfully completed high-temperature testing in a purpose-built facility, and a new funding round for a prototype flight demonstrator is under way. <S> Note that at sufficiently high speeds, airframe heating does become a problem. <S> Whether it might prove practicable, and to what extent, to refrigerate other key hotspots such as the fuselage nose or the wing leading edges must remain an open question.
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Yes it is thought practicable to refrigerate the engine intake air, though it has yet to be demonstrated in flight.
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Would it be frowned upon that with a uncommanded nose up, the pilots just do a full loop? So what I’m asking is that if a uncommanded nose pitch up happened and was so bad that it reached a pitch angle of 50 degrees, the pilots were unable to stop the pitch up by applying the control column forward, would it be justified if the pilots just applied more back pressure, ultimately doing a full loop? <Q> No airliners aren't stressed for loop maneuvers. <S> The proper action for that kind of extreme pitch attitude is to roll 90 degrees and let the nose fall, then roll level as the horizon is passing. <S> Of course if you had a nose up stab trim runaway that left you stuck with that pitch tendency (effectively a much lower trim speed), you're back to square one. <S> You have to slow down to as close as you can get to the trim speed that the nose-up-stuck stab wants to fly at. <S> You might find that you have enough elevator authority to maintain a level pitch attitude if you get the speed down to a minimum flaps up speed, say 180kt. <S> Then you can do other things to create a nose down pitching moment, like dropping the gear, and on most airplanes, extending flaps. <S> That should be enough to remove most or even all of the elevator input required depending on where the stab was when you killed its runaway. <S> In an extreme case where you've run out of options, you might even try getting passengers to move forward. <S> In recurrent sim training, a nose up stab runaway was always a more pleasant exercise than a nose down one. <S> Mostly because slowing down, and gear and flaps helped, and to the extent you had to hold continuous nose down elevator, one of you could brace your knee against the column to help with most of the push force and it was easier to hold it for extended periods. <S> A nose down stab runway was a much more difficult situation. <A> Well, in the world of radio-controlled model airplanes, there are some aircraft (e.g. long-winged gliders) that are prone to entering an uncommanded nose-down "tuck", which is best escaped by giving a firm nose-down input to fly through half of a downward loop to enter inverted flight. <S> But if I were a passenger in a plane that was doing an unexpected loop, I would probably be frowning. <S> Anyway, as far as normal (upward) loops go-- <S> Otherwise you are in danger of entering of a tailslide after running out of airspeed with the nose pointing steeply upward. <S> Very bad for the control surfaces. <S> Of course, retaining too much airspeed as you transition through level inverted flight into the start of an inverted dive <S> , can also be a very bad thing. <S> So be careful when looping. <S> Basically, a loop is never going to be a practical approach to dealing with something that is unexpectedly going wrong with a conventional full-scale airplane, unless something is seriously broken in the control system, and maybe not even then. <A> No it would not be a good idea, nor justified and it would be frowned uppon, <S> aside from the fact this is not a great idea for an untrained pilot this would simply stall the plane. <S> Most aircraft lack the thrust to do a full loop in this manner. <S> Pulling up aggressively even at full power generally leads to a "power on stall"
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In almost all cases of an unexpected pitch-up, it would be better to increase the bank angle to help bring the nose down, if elevator inputs alone are somehow not doing the job. you really don't want to mess around with off-the-cuff spur-of-the-moment loops unless you know with absolute certainty that you are entering them with sufficient airspeed and pulling sufficient G's to get well past the upside-down attitude with sufficient flying speed.
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Can a fixed-wing plane jump up by blowing air over its wings? NASA's X-57 electric plane has 12 wing-mounted propellors which drive air past the wing. This video describes how the resulting increased air velocity causes an increase in the amount of lift the wing generates. Suppose the propellors could generate enough airspeed over the wing to lift the entire plane -- could the plane then jump into the air without needing a runway? This would require that sufficient lift is generated before the propellor thrust (minus wing drag) exceeds the craft's friction with the ground -- otherwise the propellor thrust would push the craft forward some before a liftoff could occur. And that leads to my secondary question: Is blowing air over a wing a more efficient means of achieving lift than would be directing those propellors downward rather than laterally over the wing? <Q> As a partial answer to your question, air moving over a stationary (relative to the ground) wing will generate lift. <S> Videos of these incidents showed that it was lift and not force from form drag that lifted the aircraft off the ground. <S> In the case that the planes were tied down, they would come back down to earth in place. <S> Unfortunately, the force of the decent, in some cases, was still enough to damage the planes. <S> I am uncertain about what you mean by <S> “This would require that the lift generated would exceed ground friction reacting the propellor thrust... <S> “ . <S> Lift would be acting roughly perpendicular to the wings chord line, and the plane’s longitudinal, and lateral axes. <S> On the other hand, any friction created by the relative wind would be acting roughly parallel to the relative wind and the plane’s longitudinal axes. <S> The only ground friction would be that caused by the wheels touching the ground. <S> Thrust is a function of Newton’s Laws of Motion. <S> The propellers turn chemical energy (in this case electrical energy) into thermal and mechanical energy. <S> The mechanical energy is used to accelerate a mass of air. <S> The mass of the air is accelerated by the propellers creating force. <S> This force acts on the mass of the airplane to accelerate the airplane. <S> The relative wind created by the propellers would act upon the airplane in the form of thrust and upon the wings to create lift regardless of how close to the ground the airplane was. <S> P.S. Edited to include a new link pertinent to the discussion. <S> Here is a new VTOL aircraft soon to be on the market. <S> Blackfly <A> Not sure if this is on point, but there are a few videos on youtube of parked unmanned aircraft lifting off in high winds - they weren't tied down, and off they went. <S> They lift and kind of get blown backwards - probably flip over and get wrecked. <S> Its the relative speed of the air going over/under the wings that generates the lift - how that relative velocity is achieved (propeller thrust or wind) is irrelevant. <S> So to answer the question, yes, if you blow hard enough. <A> (I am not a pilot, but...) <S> This would require that sufficient lift is generated before the propellor thrust (minus wing drag) exceeds the craft's friction with the ground -- otherwise the propellor thrust would push the craft forward some before a liftoff could occur. <S> The friction between two things is proportional to the force pushing them together - that is, weight minus lift. <S> When lift equals weight and the plane can start moving upwards, the friction force is zero. <S> Some time before that, the friction is less than the thrust. <S> So, no, you cannot take off vertically with horizontal thrust because at some point before the lift exceeds the weight, the thrust will exceed the friction. <A> The variables in the lift equation (below, from wikipedia https://en.wikipedia.org/wiki/Lift_(force) ) are the density and velocity of the air flow. <S> How the air reaches that velocity is not relevant to the amount of lift generated. <S> $ <S> L={\tfrac 12}\rho v^{2}SC_{L}$ <S> where ${\displaystyle <S> L}$ is the lift force <S> ${\displaystyle <S> \rho } <S> $ is the air density $v$ <S> is the velocity or true airspeed <S> $S$ is the planform (projected) wing area <S> $C_{L}$ is the lift coefficient at the desired angle of attack, Mach number, and Reynolds number
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There have been several weather related incidences where aircraft were picked up off the ground by significantly strong winds.
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Does wearing glasses mean you automatically meet the first class medical requirements? I have been wearing glasses for a very long time. If you wear permanent eyeglasses do you automatically meet the FAA first class medical vision requirements? <Q> Certainly not. <S> Eyeglasses can't fix everything. <S> Some people have very poor vision even after correction with glasses. <S> One example out of many, would be someone suffering from macular degeneration. <A> The first class medical vision requirements are in 14 CFR 67.103 (emphasis mine): <S> Eye standards for a first-class airman medical certificate are: (a) Distant visual acuity of 20/20 or better in each eye separately, with or without corrective lenses . <S> (b) Near vision of 20/40 or better, Snellen equivalent, at 16 inches in each eye separately, with or without corrective lenses . <S> If age 50 or older, near vision of 20/40 or better, Snellen equivalent, at both 16 inches and 32 inches in each eye separately, with or without corrective lenses. <S> In other words, the FAA doesn't care if you wear glasses or not as long as you meet the vision standards. <S> If you can't meet those standards even with glasses (or contact lenses), then you won't be able to get a first class medical. <A> Your vision has to be corrected to 20/20 or something close to it with the glasses on. <S> I believe you are also required to keep a spare set available. <A> I am wearing glasses with significant difference between the eyes. <S> With the difference serious enough, putting fully correcting glasses is not possible for both eyes, because it screws up the linearity perception. <S> Straight curves look bent. <S> Not very good for a pilot while you can close one eye and then another can do alone, just without ability to percept the distance that anyway does not reach much beyond the nose of the aircraft. <S> In any case, a compromise must be made because of this difference, and when I wear glasses, my vision is not fully corrected. <S> However contact lenses are worn much closer to the eye and do not have this problem. <S> My eyes can be fully adjusted to the perfect vision with the help of two different contact lenses (-2.0 and -6.0). <S> Hence I think just glasses may not be sufficient (even if they could), but probably contact lenses would work for much wider range of cases. <S> There are also other ways in these days to correct the vision. <S> I wanted to be a pilot in the past. <S> I have never attempted, because I was deeply convinced my eyes will not permit. <S> Talk seriously with the doctor. <S> Do not repeat my mistake by deciding negatively on your own.
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If corrective lenses (spectacles or contact lenses) are necessary for 20/20 vision, the person may be eligible only on the condition that corrective lenses are worn while exercising the privileges of an airman certificate.
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Would a airfoil move backwards if you rotate it vertical Lets say i have a wing with an engine attached to it like a propellor. And now i point the nose of my airplane up untill it is vertical. Would the wing still generate lift because of the air flowing past it. Resulting in a backwards movement of the entire airplane? EDIT I am suggesting that the plane is hovering vertical not gaining or losing any altitude. This may sound very vague, so here an image hopefully to make it clearer: So just to clarify, the brown thing should resemble a propellor. the yellow line the horizontal normal orientation of a wing. and the red arrow the resulted direction of the airfoil. and the green lines the airflow. As you may have guessed i am not an expert when it comes to planes and the physics behind it all. So pls let me know if more information or clarification is needed. <Q> A practical example of your question is when a model aerobatic aircraft with a conventional aerofoil profile (ie, not symmetrical) is fitted with a sufficiently powerful motor that it can be made to hover in the vertical position. <S> This is quite a common trick. <S> The answer is yes, there is a force in the direction of the red arrow. <S> The model might drift in that direction, although there are other aerodynamic forces, torque, centre of gravity & thrust vector issues that will affect the balance, and these will change as power is increased and the model goes from hover mode to vertical flight mode. <A> It would depend on the Angle Of Attack of the area of the wing in the propeller slipstream. <S> If the flow was at the wing's zero-lift AOA, there would be no lateral force. <S> Aerobatic aircraft with symmetrical airfoils that are at zero incidence in the propeller slipstream would be that case. <S> Wayne Handley's Turbo Raven hovering act back in the 90s, where he would hover in front of the crowd for extended periods, would be like this (saw it a couple of times; my favourite airshow act of all time). <S> An airplane with a cambered airfoil, where the zero lift AOA was at a slight positive or negative angle to the stream would see a lateral component. <S> The pilot holding a hover like that would simply cancel that out instinctively with an small elevator input that slightly tilts the thrust vector to compensate. <S> This can be complicated by the need to use aileron as an anti-torque control during something like this (you need ailerons that are large and go right to the wing root so they are in the prop stream), which may modify the overall lateral lift effect. <A> Yes, that wing would create some sideways lift. <S> Whether it would actually move depends on how you are holding your aeroplane vertical. <S> Obviously it's not going to move if you've bolted it to a big, heavy, test stand. <S> The effect would be easy to counter by hovering not-quite vertically. <S> If you think about it, a propeller is just a vertical aerofoil that generates forward 'lift' when it's travelling up (and sideways and down).
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For an aerobatic plane prop-hanging, it would depend whether the aerofoil is symmetrical, and the angle at which it is fixed to the plane.
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How do STOVL and V/STOL aircraft differ? Wikipedia's page for STOVL begins with A short take-off and vertical landing aircraft ( STOVL aircraft ) is a fixed-wing aircraft that is able to take off from a short runway (or take off vertically if it does not have a heavy payload) and land vertically (i.e. with no runway). while V/STOL is A vertical and/or short take-off and landing ( V/STOL ) aircraft is an airplane able to take-off or land vertically or on short runways. Vertical takeoff and landing (VTOL) aircraft are a subset of V/STOL craft that do not require runways at all. Generally, a V/STOL aircraft needs to be able to hover. On both pages, it is stated that the respective type should not be confused with the opposite one. Essentially, it says STOVL is not the same as V/STOL and vice versa. However I have trouble understanding where the differences lie between them. I was about to clear it up on my mind when I thought STOVL definitely requires some (short) distance for the aircraft to clear before taking-off, while V/STOL aircraft are simply able to start hovering in order to take off. But apparently, it's possible for STOVL aircraft to do so if they don't have heavy payload. What am I missing here? Both are supposed to be able to land vertically so I suppose there's either a difference on the take-off or if not, there are differences on the wing structure/geometry of each type of aircraft. <Q> operational weight). <S> STOVL aircraft does not have sufficient engine thrust to take off vertically at any weight, and at higher T/O weights it must have some lift from wings to assist the T/O. <S> It may be able take off vertically at less than max. <S> T/O weight. <A> As it stands, no one has operationally deployed a fixed-wing aircraft that can land vertically, but cannot take off vertically. <S> All modern aircraft referred to as STOVL or V/STOL are, in technical terms, VTOL (as well as STOL) capable aircraft. <S> Designating them V/STOL was a matter of emphasizing that they can combine the higher useful load advantage of STOL operation with the flexibility of VTOL operation. <S> The term "STOVL" is a further attempt to distance away from the notion of VTOL as low-performance. <S> In the F-35B's case the justification is that a conventional takeoff ramp is still required for practical operations, but a simpler and more compact vertical recovery can be used. <S> Actual operational practice may dictate outright STOL operation to be preferable. <S> In short: As used presently, these terms do not carry an inherent technical meanings. <S> It's just practice, and in some cases can even be thought of as public relations choices. <A> V/STOL and STOVL are as much operational modes as types of aircraft. <S> In V/STOL, the aircraft is envisaged as sometimes taking off and/or landing vertically and sometimes using a short runway, adapting its mode of operation to the job in hand. <S> Some hybrid and compound rotorcraft can operate in STOL mode as well as VTOL. <S> In STOVL, the aircraft is envisaged as taking off from a short runway, either because it is heavily loaded or it is based there, and at the end of its flight landing vertically, again either because its fuel load is now so light that it can hover, or the destination demands vertical descent. <S> The UK Sea Harrier fleet typically operated in STOVL mode, taking off up a ski-jump and landing vertically. <S> Some aircraft are optimised for the one mode or the other and described accordingly, others are designed for both modes and the choice of description is a marketing or editorial one. <S> Weirder non-standard variants are sometimes cooked up for specialist modes or sub-modes such as VTOSL or VTOCL (conventional landing) for a vertical-launch point-defence interceptor, or STOV/SL which speaks for itself. <S> Thankfully, none has stuck. <A> You’re right. <S> V/STOL and STOVL are one in the same. <S> It would probably be better to consider the term STOVL more of a mission profile than an aircraft capability. <S> All powered lift aircraft eg Harrier, F-35B, etc. are capable of vertical takeoff and landing within certain weight limits. <S> They are not capable of vertical flight outside this. <S> The directed lift system on these aircraft do allow lift to be augmented by vectored thrust, allowing for short takeoffs and landings this way at greater weights. <S> The upshot of which is that, for certain operations, it makes more sense to a jet like that to execute a short takeoff when heavily loaded ie fuel + weapons load, fly a mission, thence, once fuel and stores are significantly depleted below max hover weight, then make a vertical landing. <S> The profile works well for ops from small helicopter carriers or unpaved, short airstrips where CTOL operations just aren’t possible. <S> Now a STOVL or V/STOL <S> capable aircraft should not be confused from a pure VTOL aircraft eg MACAIR DCX, SpaceX Falcon 9 Booster, DJI Mavic, etc., which cannot accomplish short field takeoffs and landings. <S> Even a helicopter would be considered a V/STOL aircraft as it is common for some ops to do short field takeoffs and landings when operating at density altitudes above the maximum hovering altitude for a given takeoff weight.
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To put it simply, it's about the ability to take of vertically at any mass: V/STOL aircraft can take off fully loaded (max. The distinction between STOVL and V/STOL is largely a matter of naming.
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Why isn't landing in the water a good option in an emergency? Some people say that landing on water should be considered as a last resort because it is dangerous. But why exactly is it dangerous to land an airplane in the water? Wouldn't it be safer since theoretically, water would reduce the impact? Note: I am referring to all planes (small and large). <Q> For one you can not "land on water" you can ditch an aircraft in a body of water but you would be hard pressed to call it a landing. <S> You can however, " land in a grass field " or "land on a runway nearby" or "land on a highway" all of which are substantially more controllable then trying to stall a few feet above the ocean . <S> The result of catching an edge which can dig into the water is the same or worse than belly landing on grass. <S> As others have mentioned at those speeds water is not so forgiving. <S> but historically it tends to end poorly. <S> While the miracle on the Hudson ended well Ethiopian Airlines Flight 961 did not have the same luck. <S> You can see the outcome of contacting asymmetrically is pretty devastating. <S> The secondary concern is that even in a successful ditching still puts you in a sinking airplane with potentially injured people making rescue all that much harder. <S> Although Aviation Saftey Magazine paints an interesting counter point. <A> Because in most cases landing in the water is no different from landing on concrete. <S> In fact, it could be much worse. <S> I'm not going to talk about the technicalities and physics behind it, but there are loads of reasons why you shouldn't land a plane in the water. <S> For example, the waves are a big threat.. <S> Pilots usually try to land parallel to the waves, so the aircraft isn't pushed around and endangered. <S> In the scenario that there are waves directly moving towards the aircraft, it's like running into a wall that's moving towards you. <S> And the most worst case scenario comes to the aircraft breaking apart. <S> All in all, when landing in the water, there are a lot of extra variables that pilots must deal with the execute a safe landing. <S> So if you were given a choice of either landing on water or land, try landing on land first. <S> Landing on water is always a last resort. <A> A simple answer is because you're less likely to drown on land. <S> Open sea normally has waves of at least a meter, so any landing will be a controlled crash with structural damage. <S> Part of the fuselage may be full of water very quickly, and there will be limited time to evacuate everyone, including the injured. <S> Once you're in a life-raft, exposure and hypothermia can kill in a few hours, and dehydration in a few days - and it can take that long for help to arrive. <S> 10-20mph is common for ships, even a fast warship might only do 30mph, and you could be hundreds of miles from help. <S> And that's assuming that the location beacons work, and bad weather doesn't prevent rescuers from spotting you.
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If an aircraft breaks apart upon landing, it greatly endangers the passengers and crew as the aircraft will begin to flood with water and sink.
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What should a pilot do if he does not know where he is and has no form of communication? I know this is an almost impossible situation, but... Imagine that a pilot is kidnapped and placed inside a Cessna plane. At a certain point the kidnapper jumps out of the plane, destroying the radio and taking all the aeronautical charts with him. My question is: what should the pilot do, since he does not know where he is (he does not even know which country), there are no signs of civilization where he's flying, and he has no aeronautical charts? <Q> The first thing you should do during a lost com's situation is fly the plane (that is really the first thing you should always do). <S> Even in a foreign land a pilot may be able to identify known land marks like city skylines or prominent geological features. <S> Even something like a coast line can be identifying. <S> The third order of business is to squawk 7600 on your transponder . <S> This will alert any ATC facilities pinging you on radar, that you are unable to transmit and/or hear them. <S> This falls in line with the FAA's general advice of "Aviate, Navigate, Communicate" . <S> Just a bit of an applicable side note: In the US under the FAA, and in other jurisdictions there are lots of areas that full under " uncontrolled " airspace where no radio or charts are required to be onboard anyway <S> and many pilots are proficient flying in such a situation. <S> Id even go so far as to say that a solid chunk of Piper Cubs are still flown this way. <A> First, make sure flight is stable. <S> Figure out how long you can do that, and set up flight to maximize that. <S> Now try to figure out where you can go. <S> From the Question, it sounds like there are no easy answers: no airport in sight, no giant concrete arrows pointing the way, etc. <S> in that case, pick a best direction taking into account terrain, weather, light and wind and start looking for a place to put down. <S> Climb a bit for a wider view if you’re low and can afford it. <S> Take the first acceptable place, as you’ll want to preserve your passengers (if any), your plane, and even perhaps your remaining fuel. <S> What about communicate? <S> Well, the problem statement seems to rule that out in flight, but after down SERE training becomes relevant. <S> But that’s another Question... <A> You are right, this is a pretty improbable situation. <S> But, I will give it a whack. <S> Aviate - Fly the plane. <S> Fly it at as high of an altitude possible while still keeping visual contact with the ground. <S> Just in case you lose an engine. <S> Fly it in a wide circle or holding pattern until you get your bearings. <S> Slow down your airspeed and lean your mixture for max endurance. <S> You want to conserve fuel as well as ground position. <S> No use in getting more lost quicker. <S> Navigate - Look for something identifiable. <S> Or at least something that will lead you to civilization and suitable landing areas. <S> Think of it like being lost on the ground. <S> Look for your North direction using the sun or stars. <S> Evaluate the ground for: <S> High speed avenues of approach like roadways Key terrain features Man-made obstacles like towers or buildings Find water. <S> In the US water towers (not all) are marked with location names. <S> If you find a river, you will usually find civilization close by. <S> If you find a shoreline, you may be able to find a flat area suitable for landing. <S> Fly downhill. <S> Fly towards the lowering terrain. <S> You are more likely to find a landing area. <S> If all else fails go IFR (I Fly Roads). <S> Communicate <S> - If the transponder works, squawk 7600. <S> If you have a cell phone, try it. <S> You May have to descend to get it to work. <S> Only do so if you have established where you are and if the aircraft is safe to continue flight. <S> Turn on all of your exterior lights. <S> If you see an airport, circle directly above the field at 2000 to 4000 feet AGL and look for light gun signals. <S> Land as far away from the kidnappers/highjackers as possible. <A> I think the other answers miss a few points. <S> I think we can assume the pilot knows where he was when he was kidnapped, no? <S> So the first thing to do, after making sure the plane is in stable flight, is to check the fuel gauges. <S> Assuming the Cessna is a 172 with standard tanks, it has 40 gallons usable fuel, enough for about 4.5 hours of flying. <S> So check the fuel gauges, and see how much you have left. <S> If the tanks are half full <S> *, then given the 140 mph cruise speed, you can guess that you're within about 300 miles of where you started. <S> Then start looking for familiar features like mountains, lakes, roads &c, which should be identifiable unless you're over the Amazon Basin or Canadian north. <S> That will get you oriented, and you can probably find an airport, or some other good place to land. <S> *If they're close to empty, disregard the rest, and look for a spot to land, or do a survivable crash.
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If the pilot becomes concerned about fuel (which any good pilot will at some point) then they should be on the look out for an airfield or a nice area to put the aircraft down. The second thing you should do is use visual reference points to figure out where you may be and get some situational awareness. Aviate, navigate, communicate.
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What does the flashing green-light signal (return for landing) actually mean to NORDO aircraft? Studying for the PSTAR I see that a flashing green signal while in the circuit means "return for landing" but this is not actually defined anywhere. What does that mean? NORDO = "is an aircraft flying without a radio" <Q> What I was taught that this meant was ... ... because they could not communicate with you, but they wanted you to not land on this pass ( <S> interval a mess, crossing traffic, winds maybe wrong, a dozen other things that might crop up ) <S> it was more or less <S> "the runway will be ready for you if you take another lap in the pattern. <S> " <S> This also gives them a bit of time to get all of the other aircraft in the pattern out of the way of the aircraft in distress. <S> ( And the steady green ought to confirm that on the next pass, if all things go well ). <S> Tower operators would rather get that aircraft who can't talk to them onto the ground. <S> What they want to avoid in this case (again, this is what I was taught by a salty old Navy controller when I was in flight school) <S> is that they wanted to avoid the aircraft attempting to land being "spooked" by a red light and thinking they can't land at this field. <S> And then waving off and flying off in search of another field while still NORDO. <S> The green light is the 'friendly' light between choices of red and green. <S> The Canadian Aeronautical Information Manual, which has all of the signals to include the two that are relevant to this question, can be found here . <S> The teaching that I got may no longer be current, but the lights shown to a NORDO airborne aircraft still mean the same thing as they did when I was taught. <S> Steady Green: cleared to land Flashing Green: return to land (to be followed at the proper time by steady green) <A> My understanding of light gun signals was taught to me a little differently. <S> For simplicity, I will concentrate on light gun signals for airborne aircraft only. <S> Alternating Red and Green is exercise extreme caution. <S> Steady Red is give way to other traffic. <S> Which implies that you should stay in the pattern. <S> But, you are not cleared to land. <S> Steady Green is a clearance to land. <S> Flashing Red is a request to leave the airport area. <S> This would imply that you need to remain outside the traffic pattern. <S> Flashing Green is the signal in question. <S> Based on the definitions of the other signals, this would imply that you should enter or return to the pattern. <S> But, you are still not cleared to land until you get a Steady Green. <S> So to put it into a nutshell that may be easier to remember: Green means approval and Red means denial. <S> Steady means for the runway and Flashing means for the pattern. <A> The answers above are pretty much correct, but it is nice to cite sources. <S> Since the question is relating to studying for a PSTAR and is tagged Canada, first the Canadian sources: Canada Aeronautical Information Manual (Canada) <S> Section 4.2.11 Visual Signals - Aircraft on Ground <S> 4.4.7 <S> Visual Signals - Aircraft in Flight United States <S> The Canadian signals are similar, but not exactly the same, as US FAA ATC signals, so adding these for US pilots who find this question § 91.125 ATC light signals <S> In the Airman's Information Manual (US FAA) , the signals are described in Section 4-3-13 Differences <S> Canada doesn't specify the use of alternating red/green signal <S> USA doesn't specify the use the blinking runway lights nor the firing of the red pyrotechnical light <A> Logically it would seem to mean to fly a circuit around the traffic pattern and watch for a steady green light on the next final approach.
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Put in the chief's colloquial jargon: "Flashing green lets the pilot know "the runway will be there for you when you come back for your next approach."
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What is the piece that covers the top part of tires? I would like to know the name and the usefulness of this piece that covers the top of the tire of some planes, such as some Cessnas. <Q> Those are called speed fairings. <S> They make the shape over the tire more aerodynamic and reduce drag, thus increasing airspeed and fuel efficiency. <S> This is a page in a Cessna 172R information manual that comments on the differences in performance when they are installed. <A> They have also been called "spats", though that term has traditionally been reserved for something much larger, at least in US usage. <S> Related -- <S> How can drag induced by the landing gear be reduced? ? <S> -- see all answers <S> What is "spatted undercarriage"? -- see all answers <S> https://www.eaa.org/eaa/aircraft-building/building-your-aircraft/while-youre-building/building-articles/landing-gear-wheels-and-brakes/how-to-install-wheel-pants <S> https://en.wikipedia.org/wiki/Aircraft_fairing <S> https://en.wikipedia.org/wiki/SOCATA_TB_family <S> https://en.wikipedia.org/wiki/Northrop_Gamma <A> Some people call them gear socks, but <S> yeah, if you had a problem with them and needed to notify ATC, you would probably call them wheel fairings.
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"Wheel pants" is a common term for these wheel fairings, at least in US usage, which serve to reduce drag.
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Why is paragliding not an old invention? Paraglider looks like a rather simple device for me. It does not have a complex engine that needs lots of technology to be built. It also does not need a powered aircraft just to be launched. Looking from the side I have an impression that it can cover serious distances along the ridge under right wind. While it is not convenient to have the airways bound to mountain ridges, it could still have had uses like patrolling borders or similar. I am surprised, why the master that could build a bow, or possibly sails for the ship could not build a paraglider many years ago. What are the reasons why the paraglider is relatively recent invention? Is there something complex about is I am not aware of? <Q> Paragliders as we know them depend on parawings with relatively high glide ratios and useful levels of steering. <S> Neither of these qualities were well represented in the round parachutes (even the so-called glide 'chutes) in common use before modern flat canopy glide parachutes came along (in the 1970s?). <S> Parawings as we know them were an outgrowth of these highly maneuverable parachutes, modified to have lower loading (for better sink rate) and optimized for horizontal flight, without the need to open in a near-vertical fall at terminal velocity. <S> If the knowledge had existed, parawings as we know them could have been built as early as the 1860s (when plain, round, uncontrollable silk parachutes came into use for stunt jumps from balloons). <S> The missing ingredient, as it were, was simply the knowledge that such a thing was useful and possible. <A> Ancient manned flights used either "birdman" wings or kites. <S> Nobody even understood the problem of control, never mind solved it, and both were often fatal, birdman wings especially. <S> That did not change until in the first part of the 19th century <S> Sir George Cayley defined control as a specific problem to be solved, and that would take almost a hundred years more. <S> Meanwhile, early attempts at parachutes were uncontrollable and swung wildly, sometimes fatally. <S> But even kites still had rigid sticks to hold their shape, the idea of a wholly non-rigid aircraft, shaped by the airflow, seems not to have appeared until kiting enthusiasts Francis and Gertrude Rogallo came up with it shortly after WWII. <S> The control system was key to making it work. <S> I am not sure who first invented the parawing, but Francis Rogallo subsequently adopted the technology in his day job, designing lightweight spacecraft recovery systems, and went on to popularise it along with other kite-derived flexible wing forms. <S> For a time both the parawing and the biconical delta (the latter patented by others back in 1909 and 1910, and as a kite just a year before the Rogallos' unrelated patent) were known as "Rogallo wings". <A> An airfoil made only of textiles consists of many air cells which are open at their leading edge. <S> "it's easy to make an airfoil from only strings and textiles and make a parachute", is perhaps not so easy! <S> it's non-obvious idea which is complex in design. <S> The first guy to fly a parachute thought of it when he wanted to escape his jail cell. <S> after he was freed he pursued the idea until he had the first jump from a hot air baloon in 1797. <S> it took 153 years until the parachute was shaped like an airfoil, because airfoil technology was developed in the 1900's. <S> https://www.history.com/this-day-in-history/the-first-parachutist <A> Material: <S> You cannot build today's paragliders without modern materials <S> The ropes need to withstand several kN of force while keeping diameter to a minimum to reduce drag. <S> The glider must be almost impenetrable for pressurized air, which is impossible with cotton. <S> Computers: <S> Paraglider started as a high-risk equipment back in the 80s. <S> They used to have glide ratios of 2:1 which allowed steering away from steeper mountains, but that's it. <S> Today we can actually fly with glide ratios of 8:1 and up, but those where only possible with extensive computer simulations. <S> Another aspect is safety: Today's entry-level paraglider can sort out all but the most severe disturbances without human intervention, thanks to extensive simulation. <S> Back in the days catching a harsh turbulence meant deploying your reserve chute, if you where lucky enough to have one. <S> So simply put, a paraglider looks simple, but is fairly complicated. <S> We do annual checks where we measure the individual ropes' length, knowing that a single inch of stretch could alter the flight characteristics to a fatal degree <S> - it's easy to see that it was troublesome to find these perfect proportions.
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If you build a paraglider with classic materials, it will be too heavy to fly and way too prone to collapse mid-air.
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How do single engine airplanes handle changes in torque? In multirotors, there is a regulation of torque from the rotors which keeps it stable. However, in single engine airplanes, there is only one engine with one propeller. How is the aircraft able to stabilize itself in such a case? <Q> Single engine airplanes experience torque proportional to the amount of engine power used. <S> Since the torque on most planes will be applied to the airframe in the counter-clockwise direction from the point of view of the pilot, the pilot further mitigates this torque by applying Some right rudder when applying engine power. <S> Aircraft manufacturers mitigate torque by offsetting engine placement and control surface neutral positions slightly. <S> Quick applications or reductions in engine power will still cause the torque to be noticeable enough to create a left turning tendency. <A> Most single-engine types are stable and low-powered enough that torque is not a problem. <S> The pilot will compensate in the usual way if one wing drops. <S> A pilot may also trim the ailerons to counteract it during cruise, so that the plane flies level without any extra control input. <S> Historically, it was manageable enough on the early pioneer aircraft until the Gnome rotary came along in 1909. <S> This engine not only had much greater power than anything else its size had had previously, but the whole engine spun round adding gyroscopic effects on top. <S> Unstable planes with bad habits were the norm in those days, but still had to learn to be extra careful. <S> When J. W. Dunne fitted a second-generation 70 hp Gnome to his stable D.7 tailless swept monoplane in 1911, the torque was enough to destabilise it. <S> He fitted a "torque flap" to the wing on one side and would raise it during landings, which had to be "dead stick" with the engine off because it had no throttle control. <S> His larger D.8 biplane was stable enough to accommodate the Gnome quite happily. <S> During WWI the Sopwith Camel scout fighter had an even more powerful rotary engine, and became famous for its ability to turn like lighting in the one direction but only sluggishly in the other. <S> The problem became insignificant when the rotary engine was abandoned. <S> With the advent of ever-higher engine powers in WWII the problem came back. <S> Some designers added bigger tails and/or aileron trim tabs, a few made one wing longer than the other, pilots grew cautious of over-revving the engine on the ground. <S> Perhaps the ultimate solution, which saw some use well into the postwar era, and on turboprops as well as piston engines, was the contra-rotating propeller. <S> Typically a three-bladed prop spun in one direction and another, immediately behind it and on a concentric shaft, spun the opposite way. <S> Thus torque was greatly reduced. <S> Both were geared from the same engine, with one exception: the Fairey P.24 comprised two 12-cylinder engines sharing a common crank case and each driving one of the two props, an arrangement in which half the engine could be shut down in flight to greatly improve endurance. <S> However the P.24 was dropped in favour of the less-powerful Rolls-Royce Merlin and the Naval plane it was meant for, the Fairey Battle, never lived up to its potential. <A> The rotation of the powertrain (or GMP) consisting of the engine and the propeller causes what are called engine effects. <S> These effects depend on the power supplied by the engine, the speed of rotation of the propeller and the speed of the airplane, for a given airplane.for right-hand propeller, that is to say which rotates clockwise when viewed from the pilot seat. <S> The overturning torque or engine torque is an application of the principle of Newton's third law "action / reaction". <S> Any action produces an equal reaction and of opposite direction ". <S> By reaction to the movement of rotation of the propeller (action), an antagonistic couple tends to cause a rotation of the whole of the plane in opposite direction (reaction). <S> overturning moment is more important phases of flight when the engine is operated at full capacity, particularly during takeoff or overshoot phase. <S> If this couple is very important on single-engine airplanes with high motor power (Siptfire, Messerschmitt Bf 109 etc.) <S> , it is not very sensitive on modern weakly powered aircraft. <S> This overturning torque is generally compensated during the design of the device for a given engine speed and a given speed (speed and cruising speed in general):- either by increasing the pitch angle (incidence) <S> d 'half a wing,- or by increasing the surface area of a half wing. <S> That is to say by increasing the lift on a half-wing. <S> For the other flight phases a fin compensator (tab) <S> or the stick will be used.any increase in lift <S> leads to an increase in drag. <S> So the left wing will have a greater drag than the right wing (right-hand propeller). <S> This difference in drag will generate a yaw moment on the left. <S> This yaw moment can be corrected by:- a slight timing to the left of the vertical fixed plane.(or compensator) <S> Edit:there is other torque like the roll moment,the yaw moment.... <S> Source: https://www.lavionnaire.fr/HeliceEffetsMot.php <A> In fact the effect of the torque of the engine is not big enough to significantly effect the plane's flight, although it is noticeable on some planes.
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Pilots mitigate this torque by applying engine power smoothly and gradually. As far as i know, the plane is not stabled, pilots always have to stablilize the plane by themselves when they push the throttle up.
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How do "tip jet" helicopters cancel the torque effect of the main rotor? Some helicopters use " tip jet " on the rotor blades tips such as the McDonnell XH-20 Little Henry and Hiller YH-32 Hornet . How do they cancel the rotor torque (often canceled by the tail rotor)? <Q> This is a basic physics question, involving Newton's third law of motion (For every action, there is an equal and opposite reaction.) <S> When a centrally mounted engine applies force to turn the rotor, the equal and opposite reaction creates torque on the fuselage. <S> With a tip jet, the force is applied by the jet shooting its exhaust perpendicular to the blade, so the reaction is that the blade moves in the opposite direction. <S> So the answer is that tip jets don't CANCEL the torque, they simply don't create the torque in the first place. <A> Think of the aircraft engine as one isolated system and the rotor as another isolated system. <S> In its simplest terms, torque is the force required to move mass in a circular motion. <S> Torque is caused by the engine providing power to the rotor shaft which moves the mass of the blades. <S> The torque is the interaction of the stationary engine trying to move the stationary rotor blades in a circular motion. <S> The rotor is allowed to spin freely. <S> Tip jets remove the torque being supplied by the engine via the shaft because the engine is no longer providing power to the shaft. <S> The reactive force of the jets is moving the mass of the isolated system of the rotor. <S> The rotors mass is being moved without the need to receive power input from another outside system moving it in a circular motion. <A> Think of 2 scenarios: in one you are holding a rocket shaped projectile that is inert and you throw this projectile using your arm. <S> In the second scenario you hold a real rocket, which is then launched. <S> In the first scenario you throw the projectile, and you have to counter the twisting motion of your arm because your arm is imparting a force. <S> In the second scenario you don't have to take any action because the rocket does the work of moving the projectile instead of your arm. <S> A regular helicopter is like the first scenario, the engine pushes on the rotor, so the rotors push back. <S> A tip jet is like the second scenario as the tips push themselves. <A> Ejection of the tipjet exhaust streams in different directions creates a reactive torque on the rotor. <S> This causes the rotor to spin up until aerodynamic drag exactly opposes the jet reaction. <S> So in a way you can say that tipjet helicopters cancel the rotor torque through aerodynamic drag. <S> But no torque is applied to the rotor through the rotor hub. <S> Its bearings may create a tiny amount through friction, but that is negligible.
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If you disconnect the engine from the rotor (for instance via a clutch), you eliminate the torque.
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Can lift be increased by increasing the angle of incidence of the wing? Can the lift of a plane be increased by increasing the Angle of Incidence (angle between the chord line of the main wing and the axis of the fuselage)? Meaning, can more lift be generated while the plane is in a horizontal position (i.e. not pitching nose up or down) if the wings are angled leading edge up. <Q> Yes. <S> Angle of Attack is included in the Lift formula. <S> Lift generally increases with angle of attack in a linear fashion until AOA reaches stall. <S> This is why it is not a good idea to fly at too high an AOA. <S> Better to increase Velocity. <S> Lift increases with Velocity squared . <S> The Navy Vought <S> F-8 Crusader had a " variable incidence wing " that was raised to a higher pitch relative to the fuselage for take-off and landing. <S> Interesting to note the variable incidence wing would also improve forward visibility on landing because the fuselage nose would have a lower pitch to the horizon while the wing was at a given angle of attack. <S> Trailing edge flaps also raise the wing chord incidence to the fuselage with similar benefits. <S> While in flight, most planes simply pitch the entire plane with the elevator to increase Angle of Attack. <A> Yes, it is possible and variable-incidence wings have been used. <S> The only production example was the Vought <S> F-8 Crusader , used primarily by the US Navy. <S> It had a variable-incidence wing, which tilted nose-up by about 7 degrees to give increased lift for takeoff. <S> The conventional solution of a lengthened nose undercarriage was deemed impractical for the design. <S> An earlier prototype was the German Blohm & Voss BV 144 transport of WWII, which was built in France and seems to have flown a few times around the end of hostilities. <S> Variable incidence was provided because the tail was too close to the ground for conventional rotation of the whole plane at takeoff. <S> Another rather obvious application is the tiltwing V/STOL configuration, of which several prototypes have also flown. <S> The additional lift provided by increased incidence can significantly ease the transitions between vertical and forward flight modes. <A> If I am thinking about this correctly, increasing angle of incidence would increase lift because you would also be increasing angle of attack. <S> It’s the angle of attack that’s important. <S> A better question is what are the advantages and disadvantages of increasing angle of attack by increasing angle of incidence. <S> One advantage that I can think of is a reduction of drag generated by the fuselage and empennage at low speeds such as slow flight. <S> However, there will be an increase in drag created by the wings at high speeds such as cruise flight. <S> Intuitively, you would also assume there would be an increase in stall speed. <S> How would an increase in incidence angle affect maneuvering such as banking for turns. <S> Wouldn’t the increased angle of incidence exacerbate stall characteristics even when the turn is coordinated? <S> Just throwing some thoughts out there. <A> In short, no. <S> But it depends... <S> Angle of incidence does not increase or decrease lift, only angle of attack and airspeed affect lift. <S> Let me explain - If you had an aircraft with a variable angle of incidence you could fly at a constant angle of attack while varying the incidence and have no effect on lift. <S> Picture the wing steady with respect to the airstream, while the fuselage tilts up and down; all you would affect is drag. <S> Now, if the fuselage remained constant while you varied incidence then lift would be affected, but it would be affected because the angle of attack was changing! <A> All it means is the deck angle of the fuselage will be lower for a given speed. <S> Weight being the same, the wing will fly at the AOA it needs to fly at to support the weight. <S> By increasing the incidence, the fuse will just be pointing down more because AOA will be the same for a given flight condition. <S> You have a downstream problem as well because the decalage with the horizontal tail has also increased <S> so you have to modify it <S> (move it LE up) to maintain the same decalage angle you had before to maintain the same pitch authority and trim behaviour.
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Increasing the angle of attack would increase lift until you reach the critical angle where you have airflow separation and aerodynamically stall the wing.
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Is there a standard word or phrase in the English-speaking world to describe the angle between the fuselage and the flight path / relative wind? Is there a standard word or phrase, or several alternative commonly-used words or phrases, in the English-speaking aviation world to describe the angle between the longitudinal axis of the fuselage, and the flight path/ relative wind/ undisturbed free stream airflow? Also, is one particular greek letter commonly associated with this angle in engineering texts and papers, much as "alpha" is commonly used to describe what the English-speaking aviation world usually calls "angle-of-attack"? Basically the angle we are asking about is conceptually much like angle-of-attack, but modified to mean the angle-of-attack of the fuselage rather than the angle-of-attack of the wing. Note: this question is asking about an angle that we would see when looking at the fuselage and flight path in a side view, as the aircraft flies with the wings level. This question is not asking about a yaw angle or sideslip angle. <Q> It is just angle of attack . <S> Most anything can have an angle of attack. <S> If you must be specific, you mention ' angle of attack of ... ' <S> Due to complexity of aerodynamics, most external elements of an airplane have their own local angle of attack. <S> AoA sensors measure their angle of attack, and it is usually not even converted to 'wing' or 'fuselage'; it is dubbed 'indicated' or 'measured' and all limits are set with respect to that local AoA. <S> All these angles are usually designated as $\alpha$ (alpha), but with an appropriate index, which should always be explained in the nomenclature. <S> When we talk about airplane as a whole, <S> usually the 'default' angle of attack is the one between the wind and the body frame (in the vertical plane). <S> How body frame is defined depends on the aircraft designer, but normally X goes along the fuselage. <S> Therefore, the angle of attack is exactly what you say: the angle between relative wind and the fuselage -- and not that of the wing (even though it is arguably more important). <S> Yet when we talk about aerodynamics, we may redefine the angle to mean 'angle of attack of the wing'. <S> And even offset it to be with respect to zero lift. <S> This is all fine as long as it's explicit. <S> When we talk about just wing or airfoil, then the default angle of attack will be that of this object. <A> There is a term called "deck angle", which is the angle of the cabin floor, or deck, (and normally parallel to the longitudinal axis) relative to horizontal in a given flight condition. <S> More or less the same thing as "pitch attitude". <S> These however, don't cover your question because they are relative to the horizontal. <S> I dug up this NACA report that mentions it. <S> This would be the closest term to define a fuselage's angle to the freestream. <A> If you’re talking about the angle between the longitudinal axis and the relative wind rotated about the vertical axis, I’m not sure there is a term per se except for coordination of flight. <S> The angle is not typically measured but of the angle is towards the inside of the flight path this is considered a slipping condition. <S> When on the outside of the flight path, it’s a skidding condition.
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There is another term which I think fits, called " angle of inclination ", which is the vertical angle of a streamlined body relative to the freestream.
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Is a "stalled" aircraft free-falling? If I was in an elevator in a sky-scraper and the cable broke, I would free fall and feel weightless until hitting the ground. When I cause a stall on an airplane (power-ff) and the wings stop producing lift, why doesn't the same effect occur? <Q> If the cables break on an elevator (and the safety brakes fail), you won't be in true freefall. <S> You'll still have friction from wind resistance, from the guide rollers on the rails, etc. <S> The same is true in an airplane. <S> Even if you're falling straight down, you'll still have wind resistance. <S> In addition, lift doesn't just drop straight to zero when the wing stalls (no matter what it might feel like to the pilot). <S> Here's the lift-to-angle diagram for a typical wing: ( wikimedia.org ) <S> This wing stalls at about 16° AoA. <S> But notice that the coefficient of lift doesn't simply drop to zero, it just starts descending at that point. <S> So even in a stall, the wings are still generating some lift, just not enough to overcome the weight of the plane. <A> Is a “stalled” aircraft free-falling? <S> No! <S> If I was in an elevator in a sky-scraper, and the cable broke, I would free fall and feel weightless (until hitting the ground of course). <S> When I stall an airplane(power-off) and the wings stop producing lift, why doesn't the same effect occur? <S> Because in a stall, the aerodynamic force component acting against the direction of the weight vector is not actually zero. <S> In fact, after a very short time it becomes equal to the weight vector, thus yielding a steady-state situation in the vertical plane. <S> Lift and drag, as conventionally defined <S> , both contribute to this aerodynamic force component; lift is by no means zero even in stalled flight. <S> In a stall, you are definitely not free-falling. <S> You are just flying along a very poor glide ratio or descent ratio. <S> After the first few seconds, you are no longer accelerating. <S> An aerodynamic force exists that not only limits the rate of downward acceleration, but also yields a specific downward terminal velocity, as well as as a specific forward speed. <A> It is a loss of laminar airflow over the wing, resulting in a loss of lift. <S> The response to a stall is to stop the (usual) roll induced by one wing stalling before the other. <S> Then drop the nose - most aircraft will do this by design - until you achieve a flyable speed with proper airflow over the wing. <S> The problem here is that you may not have enough altitude to reach that speed >> crash. <S> I once stalled and dropped from over 25000 (not looking at altimeter) to under 12000 before I had enough airspeed to pull up. <S> With the resulting pucker factor I bottomed out at around 7000 ft. <A> Speaking as a commercial pilot, pilot instructor and skydiver <S> I think I can answer this. <S> An aircraft has a centre of pressure, which is the lift vector that comes out of the wing and opposes the weight. <S> As you increase the angle of attack of the wing, up to around 16 degrees angle of attack, the centre of pressure (lift) moves slowly forward. <S> When you stall, the boundary layer which is the area of low pressure air sucking the wing upwards, rips off and the centre of pressure moves rearwards, behind the centre of gravity. <S> This drops the nose of the aircraft. <S> The drop of the nose reduces the angle of attack and the wings start to fly again. <S> Even if you hold the aircraft in a stall at the buffet, the wing will still drop and attempt to fly again repeatedly. <S> So, you're never in freefall, which would assume terminal velocity, you're just pitching up and down as you move forwards in the stall.
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Freefall, as a skydiver, implies no forward movement and no lift, even though many skydiving diciplines do involve both such as tracking, wingsuiting and even formation, where you de-arch to slow yourself down and rise relative to others. A stall is not a free-fall.
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Why does Boeing use a trim wheel in the 737 and not their other products? Why does Boeing use a trim wheel in the 737 and not any other products? Is the trimmed state for the 737 just more important than in the 777 ? Or even 747 ? It gives the impression that a secondary control for the trim (If the power to the pitch trim motors have been cutout) is extremely vital, seeing it features two fold out handles that are located 90 degrees apart, so a pilot has good leverage at any point in the rotation to their desired trimmed state. I take it that this style of a trim system is implemented in the 737 for a good reason, so I’m curious what makes this “style” the perfect fit. On the 747, and 777 it almost seems that once power to the pitch trim motors have been cut-out, there isn’t a way to manually move the stabilizer? I’m very aware that I could also be 100% wrong, but why not have a trim wheel in all products? Or vice versa? <Q> Trim pitch "wheels" as you describe date back to the time when turning that wheel actually pulled on steel cables that were connected to the hinge mechanism for the control surface itself. <S> This mechanical/manual system was a simple and robust method of manually trimming the aircraft and was very widely used before electronic/fly-by-wire control systems were invented. <S> Since the 737 is the oldest basic design platform in the Boeing product line, its original design dates back to a time when trim wheels were mechanical and pilots were transitioning out of still older planes into Boeing's new offerings- and those pilots expected manual trim wheels. <A> While the other answers are correct they are missing a key point: Because it was certified that way <S> When an aircraft is certified with particular equipment, changing that can be difficult and may require the filing of a MAJOR REPAIR AND ALTERATION form. <S> Its likely cheaper for Boeing to keep the trim wheels the way they are. <S> The common 737 type certificate notes that the airframe was certified against (and must be rigged in accordance with) a particular set of Boeing drawing. <S> To insure proper operation of the airplane, the movements of the various control surfaces must be carefully controlled by proper rigging of the flight control systems. <S> The airplanes must, <S> therefore, be rigged according to the following FAA Approved data: <S> Boeing Drawings <S> No. <S> ... <S> 65-45104 Control Installation <S> , Stabilizer Trim <S> I cant seem to find a copy of that drawing but it likely indicates the trim wheel as part of the system. <A> The leading edge of the horizontal stab on jets is driven up and down for trim using a very large acme thread style screw jack. <S> The Cessna 180/185 family and the Piper Cub/Super Cub/Pawnee family also do nearly the exact same thing, just with much smaller cable operated screw jacks. <S> The early jets using jackscrew driven stabs included electric motors but maintained the manual cable-drum drive out of design conservatism, up through the 737. <S> The cable system is a lot of weight and maintenance, and the loads on the jack can be high enough in some out-of-trim flight conditions where you can't actually move the surface manually until you temporarily unload the stab with a large elevator input. <S> In the case of the Ethiopian crash, they were boxed in by this problem by being too fast and too close to the ground - the elevator control inputs required to unload the screw jack so they could turn <S> it would have made them dive even steeper (Piper Cubs also suffer from this problem where the little cable drum slips and you have to unload the surface to get it to move - on the 737 <S> you just can't move it with the little wheel). <S> Then when you get to ever larger aircraft, to have a manually operated screw jack would require a cockpit wheel the size of a ship's helm, so in the late 60s and 70s, the designers developed multi-channel electrical control with sufficient redundancy to meet the single-point-of-failure risk standards without a mechanical system (they weren't "fly-by-wire" actually, more like "control-by-wire"; in CBW, the output is the same as the input <S> but it's just done electronically <S> , in FBW, the output is what a computer decides it should be after receiving the input command and may vary significantly from the actual input). <S> Anyway, bottom line is multi-channel control by wire stab systems (and FBW systems on FBW aircraft) <S> meet the risk requirements to deal with trim failures (quits working, or runs away). <S> The risk requirement for stab failures is not that high, usually categorized as "Major" in the Minor/Major/Hazardous/Catastrophic risk hierarchy, which determines minimum redundancy levels in design, and a dual channel CBW system with the appropriate controls and indicators meets that without old style cables (Boeing used that logic to justify the MCAS's sketchy architecture in the risk analysis - <S> that's really where the ball was dropped).
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It is likely that trim wheels in newer planes are a "legacy" feature, allowing pilots familiar with an older revision of the cockpit layout to transition to another newer plane in the design series.
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What is the name of the movement which is carried out by plane beginning from the runway and ending at takeoff? What is the name of the movement which begins after the plane lines up on the runway and takeoff clearance is received, and ends when the plane lifts off from the runway? Is it also called as ' taxiing '? I know that roll-out is used for plane's decelerating movement on the runway after landing; but what is the name of vice-versa? <Q> Takeoff Roll <S> As per the FAA handbook (page 5-2) Takeoff roll (ground roll) is the portion of the takeoff procedure during which the airplane is accelerated from a standstill to an airspeed that provides sufficient lift for it to become airborne. <S> And after that Lift-off is when the wings are lifting the weight of the airplane off the surface. <S> In most airplanes, this is the result of the pilot rotating the nose up to increase the angle of attack (AOA). <S> > <S> The initial climb begins when the airplane leaves the surface and a climb pitch attitude has been established. <S> Normally, it is considered complete when the airplane has reached a safe maneuvering altitude or an en route climb has been established. <A> As in, "when you line up prior to takeoff" when talking to a student. <S> When I was flying CRJs we would use the term "line up items" to describe pre-takeoff checklist items you do at the last minute while pulling out onto the runway (like selecting anti-ice, which had to be done as late as possible in the CRJ200 because its extremely hot evaporative WAI system would cook the deicing fluid on the ground). <S> As Carlo mentions, towers for all those years used the instruction "taxi to position and hold" until the change some years ago to "line up and wait". <S> It wasn't necessary to explain to pilots what that meant when the change happened. <A> This used to be known by ATC phraseology as ‘taxiing into position’. <S> I.e. were the aircraft is holding short of the runway safety area, ATC clearance for takeoff has been received, and the pilot release his brakes and taxis the aircraft into the runway safety area and lining up into a position to takeoff. <S> After a fatal accident, I believe between the DC-9 and a PC 12, this term was changed to ‘lining up’ ie “Line Up and Wait”
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I've been flying since the mid 70s and the term has always been "line up" as a generic term to describe the process of moving out onto the runway and stopping once aligned with the runway centre line.
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When do the lift and drag vectors contribute a force component along a glider's path of travel as seen from the ground? It is often said that the lift vector helps to propel a glider forwards. The lift vector has no component acting parallel to the glider's trajectory through the airmass, but in many cases the lift vector does have a component acting parallel to the glider's trajectory as seen from the ground. Note that for a given airspeed, the direction of the glider's trajectory through the airmass-- i.e. the direction that is exactly opposite to the "relative wind" that is "felt" by the glider-- is not affected by sustained updrafts, downdrafts, headwind, or tailwinds. But this is not true of the glider's trajectory as seen from the ground. A glider in a powerful mountain wave updraft may be rising straight up as seen from the ground, while the trajectory through the airmass will still be the normal glide path that would be obtained at whatever airspeed the glider is flying at. Under what circumstances does the lift vector of a glider contribute a force component along the glider's path of travel (trajectory) as seen from the ground? Under what circumstances does the drag vector of a glider contribute a force component along the glider's path of travel (trajectory) as seen from the ground? Likewise for a powered airplane. Note -- to avoid any possible ambiguity, please be aware that this question is using the word "lift" exclusively to mean an aerodynamic force generated by the aircraft, not to mean rising air. These are two completely different things. Note -- the scope of this question is meant to be confined to linear (but not necessarily horizontal) straight-line flight with constant airspeed and groundspeed, at least over the short term. We're assuming the glider (or airplane) is flying in an airmass that is locally uniform. In other words, if the glider has entered a thermal updraft or penetrated through an abrupt wind shear or flown from sinking air into a ridge updraft or wave updraft, we're assuming that it has been in the new airmass long enough to come into equilibrium, so that net force is zero for the time being. This is not a question about " dynamic soaring " as practiced by the albatross over the open ocean, r.c. glider pilots flying in loops on the lee side of the hill, someone trying to put into practice Taras Kiceniuk's ideas about exploiting the boundaries between still air and downdrafts as a source of energy , etc. Those subjects are worthy of an ASE question, or many questions, but this is not that question. <Q> In thermals. <S> More precisely: Every time when the updraft strength increases. <S> The glider will continue on its original path due to inertia while the airflow will have a positive angle when referenced to the path of travel. <S> Now the aerodynamic force will point slightly forward and accelerate the glider. <S> Experienced pilots use this by pulling more than 1 g when flying into a thermal and less when updraft strength decreases. <S> This helps them to gain some more energy from the rising air. <S> Drag is per definition the part of aerodynamic forces parallel to the flow direction, so for drag the answer is: Always. <S> With changes in vertical airspeed, the drag component parallel to the direction of movement will merely change with the cosine of the angle between the aerodynamic and the kinetic coordinate systems. <S> If you insist on excluding changes in vertical air speed, your question will have no answer regarding lift. <A> Any glider is powered in part by its lift vector at all times when in normal flight (as opposed to a loop, roll, or other aerobatics, where a reserve of kinetic energy is used and often partially converted to potential). <S> The lift vector is always angled slightly forward when in gliding flight. <S> The energy for this comes from conversion of potential energy (in the form of altitude) into kinetic energy (in the form of forward speed). <S> Potential energy, in turn, for a glider, is in general supplied by rising air (initially for each flight, some is given by the launch assist -- whether aero tow, ground tow, winch/bungee, or by rolling/running down a slope into ridge lift). <S> Drag, on the other hand, by definition is always opposite in direction to the velocity vector, so will never have a component that adds to current velocity (though if the glider is, for instance, in a deep stall with tail down, there may be a drag component "forward" in the direction the glider's nose is pointed). <S> For powered airplanes, there will be times when there's a lift component that acts to increase forward speed (for instance, when descending more or less steeply at low throttle), and times (most steady-state flight) when lift contributes to drag -- which still, by definition, acts against current velocity vector. <A> "As seen from the ground" will be the net trajectory of the gliders <S> vertical and horizontal velocity components added or subtracted from the vertical and horizontal velocity components of the air (discounting the third axis for now). <S> We consider the theoretical uniformly moving air mass and the relative wind <S> the glider creates in flight. <S> As discussed many times on this site, a perfect circle in the air will look a lot different as a ground track if there is wind. <S> A glider with an airspeed of 40 knots may be motionless "as seen from the ground". <S> Finally, one of the keys is to consider that weight is subtracted from any vertical drag or lift vector components, the remainder is balanced in the glider velocity and direction with respect to the airmass .
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Logicly, the answer is always, with the caveat that the air mass movement velocity and direction must be considered, and yes, along all 3 axes.
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Why is the Piper PA-23 considered a bush-plane, while the Beech 95 Travel Air is not? The Beech 95 Travel Air was developed as a direct competitor with the Piper PA-23 . The Piper is considered a reasonably ok bush plane, yet the Beech 95 is not commonly seen as a bush plane (I don't think I've ever seen a Beech 95 on floats). What difference makes that the one is suitable as a bush plane, while the other is not? Beech 95 Travel Air Piper PA-23 <Q> Without getting into the details of the two, there are going to be 3 factors: Landing Gear suitable for rough fields. <S> Decent size cargo loading doors and cabin with cargo provisions. <S> Power to weight ratio suitable for short rough fields. <S> Neither of those airplanes are really purpose-built for bush operations, but to the extent they have those characteristics they could be said to be more or less suitable. <S> When the US Army was looking at the DeHavilland Canada Beaver , which WAS specifically designed for bush operations, being designed in response to an operator survey, there was a hue and cry from the US aviation lobby, prompting the Army to have a fly-off with the Beaver vs a motley assortment of "utility" aircraft put forward in haste by various manufacturers (including the Travel Air IIRC, and the Cessna 195 ). <S> The Beaver won without much difficulty, and the US Army went on to take nearly 2/3rds of Beaver production. <A> Both the question, and this answer, are largely opinion based. <S> The PA-23 designation includes both the Apache and Aztec, so any answer should really include both the B95 Travel Air and B95-55 Baron. <S> The Apache and Travel Air had similar performance capabilities, and so did the Aztec and Baron, so that is not a factor. <S> Maintenance and reliability can be factors, but difficult to quantify. <S> Piper built 2047 <S> PA-23 Apaches and 4930 PA-23 <S> Aztecs, while Beechcraft built only 720 Travel Airs and 3,651 Barons. <S> So the popularity of the PA-23 in general, and "in the bush" probably has a lot to do with the fact it was put into production first, and was also cheaper to buy. <A> This is right at the edge of recollection for me, but my memories of Australian, Pacific & SE Asian general aviation in the 60s & 70s are that the Apache was largely reviled as underpowered & not suitable for even slightly marginal conditions or use. <S> It was never spoken of highly by pilots. <S> I remember them as having a much more luxurious interior to Pipers & Cessnas. <S> It's possible they were better soundproofed. <S> The Aztecs, on the other hand, were everywhere. <S> Government departments, flying schools, charter operations, 3rd level transport, aerial survey, mail delivery, inter-island services, you name it. <S> They were sturdy & sufficiently well-powered enough to deal with short, unpleasant airstrips regularly, while carrying maximum loads. <S> They were reliable, & usually well-liked by pilots & operators. <S> This niche was (sort of) shared with the slightly larger mid-sized 4xx Cessna twins & Britten Norman Islanders, but I recall few Barons. <A> Setting aside how do these two planes fly, it is enough to see how do they stand on the ground. <S> It does not look possible to drive over meadows with a car that has bottom that low and the wheels that tiny, so how could you land, take off? <S> Also, the propeller is so low that seems ready to dig into the first mole hole on the way. <S> I think they both clearly require some prepared strip. <S> See the Beaver for comparison below ( source ). <S> I think these two aircraft in the question are not a real bush planes, none of them.
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While the PA-23 was used more in the bush, neither aircraft can really be considered a "Bush Plane". The Beechcraft (in the above markets) was almost certainly more expensive to buy, more expensive to maintain, somewhat fragile, & considered a nicer, more up-market aircraft.
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Why do flaps retract? Why do flaps retract? I know, it might seem obvious at first, because of drag, but instead of retracting the flaps, can't they just make the flaps flexible enough to get into a reduced drag position, and act like an extended wing? Maybe there is a reason we should look into this technology, since it could really help out in terms of climb rate. Or, was this already looked at, but engineers decided something was wrong about it, and threw the idea away? And by the way most of the answers involved automatic retraction of the flaps, even though I never said anything about making the flaps being automatic. Just a disclaimer. <Q> Flaps retract in order to reduce wing area. <S> This has several advantages when flying fast: <S> The higher wing loading (weight per lift-producing area) reduces gust loads. <S> When hit by a vertical gust, the angle of attack increases suddenly, and so does lift. <S> If this happens at high speed (more precisely: At high dynamic pressure), the lift increase might overstress the wing. <S> A reduced area will only produce so much extra lift before the wing stalls, which limits the extra lift from gusts. <S> Less exposed area also means less friction drag. <S> Your flexible flap proposal would still leave both sides of the flap exposed, adding more surface for friction drag. <S> Put another way, the higher wing loading shifts <S> the lift coefficient up which generally improves L/D at high speed. <S> Retraction closes the gaps between wing and flap sections. <S> While those gaps are important to maximize the lift coefficient for the lowest possible landing speed, they increase drag at all lift coefficients. <S> The retraction mechanism is heavy and increases maintenance cost, but it is worth it. <A> e.g. during take off and landing required lift is much higher than maintaining a constant altitude at cruising speed (the high drag during landing also helps to reduce speed), so the flaps are extended during take off and landing. <S> If the flap is flexible so that it will adjust automatically to the minimum drag position <S> then the pilot will not have control over the lift generated. <S> Even though there are other ways of controlling the lift and drag, using flaps is one of the fastest way, which gives much better control to the pilot. <S> Flaps are necessary to control the airplane efficiently during take off, landing, turbulence, bad weather and several other situations. <A> Plain flaps are as you suggest, just sections of the trailing edge that can be turned down. <S> That helps slow the plane for landing and gives a little extra lift, but for a plane to fly slowly and safely you need as much wing area as possible. <S> So next up the scale are split flaps, which are just the underside section of the trailing edge. <S> When these lower, the upper part remains <S> so wing area is not reduced. <S> More effective still are flaps which extend backwards, actually increasing the wing area, as well as downwards. <S> Leaving these flaps extended and just raising them in level flight is not viable, as they create excessive drag and are subject to excessive aerodynamic forces when the plane tries to accelerate to cruising speed. <S> Flexible flaps are also not a viable solution, because the air at the trailing edge is always turbulent to at least some degree and movable surfaces in this position are prone to flutter, in which they vibrate rapidly up and down. <S> This leads both to undesirable handling effects and, ultimately, structural failure. <S> Flaps have to be held rigidly in place when retracted. <A> Believe it or not, "flexible" control surfaces are a secret to competition throwing gliders, where less pitch up is needed for the throw (to keep it from looping at high speeds) and more for staticly stable gliding once it slows down. <S> These uncontrolled gliders, generally made of paper, have their elevator trim as a surface that flattens at high speed and springs up when aerodynamic forces are lower. <S> On manned aircraft, there are several different flap settings a pilot may wish to use for extra lift and/or extra drag. <S> These positions must be rigidly held to control the aircraft. <S> Having them move without pilot command would be unpredictable, there for, unsafe.
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Flaps are used to control the amount of lift and drag required during flight.
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Why do the ratio of proppeler plane over jet engine seems to have change in Bucarest airport during the covid19 crisis? I live in a village very close to an (intl) airport: Bucharest "Henri Coanda" International Airport . Now, due to lock-down caused by covid pandemic, I noticed - at least today when I spent most of the time outdoors - that all planes that flew over/around our location were propeller, none of them was a jet-plane. Companies that normally operate flights on this airport: KLM, WizzAir, Alitalia, Delta, Aegean, Air France, Tarom, etc. The main types of aircraft that normally operate on this airport are: A318, ATR42/72, B737, etc. Do you have any idea why only propeller-planes these days? I don't think it's a coincidence or just an impression, so I guess there must be some logical explanation. <Q> I have no idea about Bucharest specifically, but at least in the US, many GA pilots are taking advantage of the significant reduction in airline traffic to fly into big airports <S> they're normally not welcome at. <S> And, for the most part, ATC is welcoming these GA flights because they're bored too. <A> It depends on where you are located. <S> In the US, vacation travel has dramatically dropped but not completely subsided. <S> Business travel for the road-warrior/frequent-flyer types has dramatically dropped but not completely subsided. <S> There are people who work in essential service operations that still require air travel. <S> Cargo distributed by air has not declined. <S> It may even have increased. <S> Individuals and companies that own their own aircraft are still flying. <S> Just not with quite the same frequency as before Covid 19. <S> These aircraft are typically smaller aircraft that are prop or turboprop driven. <S> Think about the complete airspace shutdown during 9/11. <S> Any military aircraft in the air was drastically more conspicuous. <S> In the current Covid 19 environment, a normally scheduled air photography, air survey, utility/pipeline inspection, Part 141 pilot training, etc. <S> flight will still go on as scheduled (depending on the company, client, and location). <S> It will just stand out like the proverbial sore thumb. <S> Case in point, the DFW area is still very busy airspace. <S> Just not as busy as before Covid 19. <S> It may still be busier than it was during the economic recessions of the past 50 years. <S> Aviation is economically driven. <S> There are fewer pilot training flights during Covid 19. <S> But, it has not stopped entirely. <S> Especially with the number of foreign airlines sending their cadet pilots to the US for training prior to the pandemic. <S> Plus, Texas has a plethora of airports (big, small, civilian, military, public, private, and mixed use). <S> Small prop and turboprop aircraft can use any and all of them except private (except by permission) and military. <S> It may be helpful to check the registration of the aircraft still flying if it is possible where you live. <S> This will give you more of an answer of why they are flying. <A> I think this is just the case for your airport because nowadays, it's actually the opposite for the big international airports. <S> But, some international airports are actually mainly regional, even though they say they're international. <S> So, that might be why. <S> Another possibility is GA planes. <S> Some international airports still accept GA flights, even big hubs like Vancouver and Chicago! <S> But, there are benefits of having propeller planes. <S> Firstly, they're more fuel-efficient, secondly, they're easier to fly in a pilots perspective, thirdly, they're easier to maintain, and much more.
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It could also be that a lack of air traffic has made any air traffic stand out.
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Is there a proper term to use when you're referring to the total number of people on an aircraft, including both the passengers and crew/pilots? I've found that often when people quote the number of passengers on an aircraft, they exclude the crew/pilots, which they'll provide separately. Is there a proper term to use when you're referring to or asking for the total number of people on the aircraft, including both the passengers and crew/pilots? <Q> CAP 419 (the UK CAA radio telephony manual, see the glossary) uses 'POB' which stands for '(total) persons on board' <A> I would answer xyz POB if asked the question. <S> It's a standard enquiry at some airports after landing, together with aircraft registration <A> <A> Souls on board. <S> Living people on board, cadavers do not count. <A> See https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap5_section_3.html which deals with emergency reporting: Table 5-3-11 DM57 (remaining fuel) OF FUEL REMAINING AND (remaining souls <S> ) SOULS ON <S> BOARDNote - N response attribute Report indicating fuel remaining (time) and number of persons on board. <S> (remaining fuel) ENDURANCE AND (persons on board) <S> PERSONS ON BOARD <S> While for VFR and IFR flight plans 'persons' is used: <S> 91.153 VFR flight plan: Information required.(a) <S> Information required. <S> Unless otherwise authorized by ATC, each person filing a VFR flight plan shall include in it the following information: (8) <S> The number of persons in the aircraft, except where that information is otherwise readily available to the FAA. <S> 91.169 <S> IFR flight plan: <S> Information required.(1) Information required under §91.153 <S> (a) of this part;
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The term "complement" is sometimes used for the total capacity of the craft, as in "it has a full complement of passengers and crew on board."
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For general aviation small aircraft flying VFR under 10,000 feet, can I use my phone GPS for navigation in the US? For general aviation small aircraft flying VFR under 10,000 feet, can I use my phone GPS for navigation in the US? So no onboard GPS (which are expensive), no VOR/DME, of course there is always dead reckoning and pilotage. <Q> Can you do it? <S> Sure. <S> It is recommendable? <S> That depends. <S> If you are planning to use it as your primary source of navigation, then I would say definitely no. <S> There's a reason they are expensive. <S> The same cannot be said for your phone GPS. <S> But, if you remain aware of your position by other means (visually recognising landmarks and cross referencing them with aeronautical charts) then sure, you can use your phone GPS as an additional source of navigational information. <S> Just keep in mind that if the GPS suddenly fails, you should be able to continue the flight normally. <S> If you can't, then it means you are trusting the GPS more than you should. <A> A handheld (or yoke-mounted) GPS such as the Garmin 76S <S> (very ancient now) is very inexpensive and quite useful for VFR navigation, especially for choosing the right heading to end up where you want to go despite crosswinds, and for estimating ETA. <S> For seeing airspace boundaries or having quick access to the location of nearby airports in case of an in-flight problem, something fancier like the IFly700 (also ancient now) is more practical and still not expensive. <S> These days programs similar to what is available on the IFly700 can be run on inexpensive tablets. <S> Using something like one of these options as an inexpensive independent tool in addition to your phone would give you a substantial amount of redundancy and help support a "yes" answer to your question. <S> You may find it most practical to rely mainly on your phone while keeping the other device stashed away somewhere where you can reach it easily if the phone stops working for some reason, or you may find it advantageous to keep the other device powered up and running in addition to your phone. <S> I've even used two devices at the same time while flying a hang glider, which seems like complete overkill, but there were definite advantages to being able to see two screens displaying different sets of information at the same time without pushing any buttons to switch back and forth. <S> You may find this ASE question to be related/ <S> helpful-- <S> Why might a moving map Android app consistently record altitude off by 120 feet? . <S> You may have better luck finding information about good apps to run on your phone for in-flight navigation as well as for saving a record of your flight-- <S> and there are many-- in various sport pilot discussion forums, perhaps the EAA forum, etc. <S> Answers to your present question will likely focus on "is it a good idea to navigate this way?". <A> The answer is yes you can use your phone for navigation, if you remain VFR in VMC in the US National Airspace Space. <S> You just must continue to maintain visual reference to the ground and be able to abide by airspace rules (don’t bust any controlled airspaces like A,B,C, or D, SUAs, etc.). <S> There are no navigational equipment requirements for your aircraft other than to have an operational magnetic compass. <S> Your other equipment dictated in Title 14 Part 91.205(b) are more for general flight than they are for navigation. <S> That being said, you should not use your phone as your primary means of navigation in any scenario. <S> Instead, rely on your piloting skills as primary and the phone as back up. <S> Have a navigation plan. <S> Make a navigation log. <S> Have well defined landmarks and visual reference points along your route. <S> Have a calibrated compass and compass deviation card as well as an accurate clock with hours, minutes, and seconds. <S> Be able to do compass turns and timed turns. <S> Have an accurate/updated sectional chart, a plotter, and an E6b (electronic or manual). <S> Etc. <S> Smart phones, tablets, and apps have come a long way in recent times. <S> The GPS receivers can get an amazing amount of accuracy for what they are. <S> You don’t even need a WiFi or cellular data signal depending on the app you use. <S> I have been able to track my flight as a commercial passenger or my hiking, biking, or driving in foreign countries without an internet signal. <S> But, don’t rely on them in the air when it matters. <S> I’ve had my phones shut down after the ambient temperature reached 104°F (40°C) on bike rides. <S> I have had my tablets shut down on cool days in the C172 with the windows open just because they spent the entire cross country trip in direct sunlight in my lap. <S> Good old paper and a manual E6b don’t suffer from these drawbacks.
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Aviation GPS units are designed to be used on aircraft, they are reliable and have airspace maps.
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Why did some Spitfire variants have their wings clipped? Some Spitfire variants have clipped wingtips instead of the round, elliptical wingtip. The reason for this is to increase the roll rate and low-altitude performance. My question is: How would clipping the wings of an aircraft increase its low altitude performance? <Q> It would increase the roll rate, and it would increase the maximum possible airspeed at lower altitudes. <S> Generally speaking, decreasing the wing loading doesn't help to maximize the achievable airspeed unless an aircraft is near its service ceiling. <A> It apparently increased the roll rate of the aircraft and made a more optimal design for low altitude operations and ‘air-to-mud’ work happening more and more near the end of the war. <S> The cropped wing Spits were often paired with superchargers equipped with cropped impellers optimized for lower altitude flight, though this was not always the case. <S> It also improved manufacturability over elliptical wing Spits. <A> As Pierre Henri Clostermann says in his "Grand Cirque": Spitfire V: nickname:clipped,cropped,clapped Clipped = tip of clipped wings Advantage:increased speed and lateral maneuverability. <S> wings reduced by about one meter. <S> Disadvantages: this reduces the bearing surface and increases the marginal vortices cropped <S> the RR Merlin's compressor rotates faster, and increases the intake pressure ... <S> This has the effect of increasing the amount of air entering the engine, while the displacement remains the same. <S> The Merlin of these series (around 40) gives around 1,650 CV at ground level, while the XX series (approx.) <S> Of the classic Spitfire Mk. <S> V give only 1,200 (below 10 000m) <S> The downside is that is that an inflated engine is less reliable and it lasts less time <S> Other disadvantages: that at 3500 m=50 cv and the guns have only 60 shells each against 145 in the Spitfire IX! <S> Clapped=literally rotten personal appreciation of the time ... of the pilots !!!
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At low altitudes, increasing the wing loading by reducing the wing area often increases the maximum achievable airspeed, by reducing profile drag.
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Why is this airplane flying in circles randomly? This G650 has been flying around for over an hour now. Is this somebody with a mechanical problem who is burning fuel before returning to their airport of origin? <Q> What you observed is probably a Gulfstream production test flight, either an initial or a snag clearance flight, or possibly a Customer Acceptance from Savannah Air Center, which is a completion center across the ramp from Gulfstream. <S> (I think they have a test operation in Wichita), but production flights are far more common. <S> The manufacturer will have designated test areas by agreement with the appropriate ATC units, with specific boundaries, and they will flight plan into the test area for production test flights (aircraft coming off the line) where a Functional Test Procedure, usually taking several hours to complete, is performed. <S> The ATC clearance will be to maneuver anywhere within the test borders, with a block altitude clearance they are free to operate within, until they need to go higher or lower for different tests and request a new block. <S> The pilot flying will be steering this way and that pretty much randomly, within the test area borders, while the other pilot performs systems tests, and the two of them will do a number of flight tests where they operate the airplane to, but not beyond, it's certification margins (things like stalls, engine shutdown/relights, yaw damper function, anti-ice tests, those sorts of things). <S> The airplane will return with or without snags, and the plane will get snags cleared, and go back out for another flight to check the snagged items. <S> On a corporate aircraft it'll then go on to a Completion Center (usually a separate company selected by the buyer for high dollar corporate a/c) for the interior. <S> Once the completion Center is done the interior, the customer or a customer's agent is taken on a Customer Acceptance flight before accepting the a/c. <S> They will go through the cabin to make sure everything is perfect in the cabin, both fit and system wise, getting it fully cold-soaked to make sure valves don't freeze, and subject to pressurization changes that can make interior panel joints open up (and I mean perfect - the slightest flaws in panel fits will be snagged). <A> The fact that it's near Savannah and tracking within a confined airspace, I'm fairly certain this is a flight test being carried out by Gulfstream. <A> I would second what John K said, it’s most likely a GAC factory flight test or demonstration flight. <S> Also with the airplane identified as GLF6 and, most likely going be the call sign “Gulf Test six” <S> would pretty much confirm that suspicion. <S> You will also see similar flights down to Brunswick Golden Isles airport (KBQK), as Gulfstream does a lot of flight test work down there as well.
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It could be possibly an experimental test flight if Gulfstream runs experimental flying from Savannah
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When does ATC contact the pilot for a frequency change? Usually, when the aircraft enters a new flight information region for example, ATC will ask the pilot to enter a new frequency. I'm curious about when they do. Is there a rule about it (in an IFR situation)? I assume it may be different between EASA and FAA regulations. Thank you. <Q> The entire sky and all airports are divided into ATC areas of responsibility. <S> Whenever a flight moves from one area of responsibility to another, the pilot needs to change frequency to talk to the next controller. <S> A flight can only be under the control of one single ATC unit at any one time, which usually equates to being on one single radio frequency. <S> When under ATC control, pilots do not change frequencies unless instructed to do so. <S> For the en-route phase, airspace is divided into sectors, defined as three dimensional areas. <S> Each sector will typically have its own dedicated frequency, although sectors can be combined in which case several sectors may operate on the same frequency. <S> On the ground, depending on the size of the airport, there can be multiple different frequencies. <S> It is common to have one tower frequency per runway, and then one frequency for the taxiways - or possible several, if the airport is large and complex. <S> ATC will instruct the pilot to change to the next frequency at the latest when the flight enters the new area of responsibility, and often a minute or two before that. <S> At that point, the flight will already have been coordinated between the controllers, so the controller of the downstream area of responsibility knows it's coming. <S> Specific rules for transfer of communication is agreed between adjacent ATC units in letters of agreement. <S> An example from Copenhagen: AIP Denmark EK <S> AD 2 - EKCH - AREA OF RESPONSIBILITY <S> Each color depicts an area of responsibility, and (this is a bit simplified but) essentially one specific frequency that pilots should be on when they are within that area. <S> You can see that each runway (roughly) has one frequency, and the apron area where aircraft park has another. <S> In the air, it can look something like this: <S> AIP Denmark EK <S> ENR 6.2 - 3 <S> The dashed lines indicate borders between areas of responsibility, and the bold text indicates the frequency to use in that area. <S> Again, the controller will instruct the pilot to change to the next frequency when crossing from one area to another. <S> Further reading <A> The controller will request the pilot changes frequency either when the controller is ready for them to do so: <S> G-ABCD, Contact Anytown Control 123.000 <S> Or, they can request change at a particular moment, for example: <S> G-ABCD, at Waypoint Contact Anytown Control 123.000 or <S> G-ABCD, when passing FL100 contact Anytown Control 123.00 <S> That's it really - there isn't some huge preamble or discussion. <A> In IFR flight the ATC controller will not tell the pilot to change frequencies until he has coordinated with the next sector. <S> The next controller must check for conflicts before he can accept a new aircraft to his sector. <S> More and more this is done through Controller–pilot data link communications (CPDL) text messaging and no radio call is needed to tell the pilot to change frequencies.
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When taxiing from one area to another, the controller will instruct the pilot to change to the next frequency.
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Why does the second floor of the Boeing 747 occupy only part of the plane? Why does the second floor of the Boeing 747 occupy only part of the plane, while the second floor of the Airbus a380 occupies the entire space of the plane? <Q> The basic design of the Boeing 747 was originally developed to for the US military's CX-HLS program for a large cargo aircraft. <S> One of the main requirements of the program was for cargo to be loaded from the nose, and placing the cockpit above the main cabin <S> made this possible. <S> The Lockheed <S> C-5 Galaxy was selected, but Boeing carried the same features over to the 747. <S> In the 1960s when the 747 was being developed, some believed that supersonic aircraft would be taking over the long-haul travel market. <S> The relatively short "hump" was retained not for extra passenger capacity, but so that if the passenger market dried up, they could keep producing the aircraft for the cargo market. <S> Boeing did extend the "hump" further back to add capacity on passenger versions, first on the 747-300 (and later retrofitted to a few -100 and -200 planes), and again on the 747-8I . <S> Extending the second deck all the way back would create too many major changes to the structure and aerodynamics of the airplane, essentially making it a completely new model. <S> Boeing did study a full double-deck model to compete with the A380, but opted to focus on a smaller, more fuel-efficient market with the 787 instead. <A> According to Joe Sutter, the chief designer of the 747, his team came up with the concept of a wide body as an alternative to a double decker. <S> More efficient use of the available volume, and faster emergency egress. <S> It took some selling, and several mockups, to persuade Pan Am to accept this new and radical design. <S> The 747 was initially conceived a stopgap effort in the mid 1960's, expected to be overshadowed by the 2707 SST under development. <S> As such, it was modified for use as a cargo aircraft, by moving the cockpit above the main cabin, to facilitate a front opening nose for rapid cargo load/unload. <S> The thinking was - when the 2707 came out, they could still use the 747 for cargo, where high speed wasn't required. <S> The fairing was added behind the cockpit for aerodynamics, and the extra space used for passengers. <S> Originally, Sutter's plan was to have crew quarters there, to which Juan Trippe of Pan Am replied - Hell no. <S> We're putting paying passengers there. <S> When the SST was abandoned due largely to skyrocketing fuel costs, the 747 was front and center as the first large airliner to make use of the more efficient high bypass turbofans, lowering fuel usage at a time when fuel costs had gone through the roof. <S> Why didn't they extend the upper cabin through the entire fuselage, as the A380 did? <S> The requirement for 400+ passengers from Pan Am was met by the widebody design. <S> Remember that when the 747 debuted, the typical international airliner (707, DC8) carried 150 passengers. <S> So it was already a huge leap. <S> Even more would have stretched the engineering challenges considerably, when the customer wasn't asking for that. <A> The "hump" was extended aft to improve its aerodynamics . <S> Back then a dual-deck airliner was being considered to maximize passengers, but it would have been too heavy. <S> But that was no longer the case for the A380.
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The 747's cockpit was raised for a different aviation market.
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Why does wingwalking use only biplanes? Wingwalking is an aerobatic discipline with shows such as this one .The definition of wingwalking from Wikipedia gives no other alternative than using biplanes: Wing walking is the act of moving along the wings of a biplane during flight [...] (source: Wikipedia, as of 26 February 2020 ) When searching for images on the web, I can only find biplanes , mainly stearman but also other biplanes . For me, it seems that any aircraft with high wings or parasol wings can do the job, so why do they only use biplanes? <Q> It doesn't only use biplanes, searching "wingwalking monoplane" provides these examples, of some low wing monoplane and high wing monoplane. <S> Whatever the aircraft, it has to be able to fly slowly. <S> ( source ) (not 100% about this one <S> but it looks like one Klemm aircraft) ( source )(Here one quite rare danish SAI KZ III equipped with a hatch behind the wing, allowing acrobat Palle Johnson to get out.) <S> ( source )(Jaromir Wagner, Czech wingwalker holding speed record wingwalking at 270km/h here on a Britten-Norman Islander aircraft) <A> 3 reasons: <S> The really obvious one; biplanes had the interplane structural network to hang on to when doing the wing walking. <S> It's a heck of a lot safer for the wing walker. <S> Even today, most of the wing walker acts use Stearman or Waco biplanes. <S> They generally have lower wing loadings than comparable monoplanes <S> so could fly slower. <S> They were readily available as WWI surplus in the 20s when the whole Air Circus business was getting underway. <S> Equivalent monoplanes would be new production and much more expensive to acquire. <S> So while there are/were monoplane wing walker acts, they weren't true "wing walkers". <S> The original wing walkers walked out from the fuselage to the wing tip, and the usual trick on the Jenny was to get down and hang from the wing tip protector hoop that extends down below the interplane struts. <S> It was only possible on a biplane because there was structure and wires to hang on to. <S> The monoplane acts are great stunt acts, but they aren't true wing walking acts because no, you know, walking along the wing , goes on. <S> They have a brace to let someone stand up above the fuselage, but you won't see any of them walking out along the wing to the tip without any kind of aids, as you do on a biplane. <A> I'd offer that it's due to the speed of the plane. <S> I have seen it done with mono-wing planes as well, but it's rare, as others have also mentioned. <S> The rationale for biplanes is likely twofold: <S> The additional weight in the plane or just the stress on the plane itself combined with lower airspeed means that the plane needs all the help it can get to remain airborne, especially when stunts are involved.
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Two wings means more aerodynamic lift. There's a nostalgia element to be considered, now that the style of plane is out of fashion, and has been for some time.
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Why do turbofans go faster than turboprops? Can someone explain why turboprops are less effective in terms of thrust than turbofans? But at the same time, why turboprops burn less fuel? For example, the Bombardier Q400/De Havilland Dash 8 has a fuel burn of 2.79L/seat/100km, whilst the 737 MAX 8 with the same number of engines burns 2.93L/seat/100km, but the Bombardier has a max. cruising speed of 360 knots and the Boeing plane can go up to 526-527 knots, even though it's heavier. <Q> To generate a given thrust, a turbofan accelerates less air but faster than a turboprop. <S> This means that turbofans can fly faster. <A> It’s all dependent upon what operating speeds your aircraft will be in. <S> Propellers can move a great volume of air at slow speeds but accelerate the gas to a lower exit speed than does a turbojet or a turbofan. <S> This is the principal reason that a helicopter is the most efficient means of VTOL flight out there for a heavier than air aircraft. <S> But as speeds increase, the the specific impulse drops and the propeller efficiency drops off with it. <S> At around 400-500 mph, the specific impulse of a high bypass turbofan becomes superior to the turboprop, as, while it moves less air than a turboprop, it can accelerate the smaller air mass to a much higher exit velocity. <S> This trend continues through low bypass turbofan engines, turbojets and then ramjets. <S> And as pointed out turboprops have a beta and reverse pitch range which can produce reverse thrust. <A> Turboprops are less fast because of the mechanical constrainsts at the blade tips,efficiency and noise near the speed of sound. <S> For reverse thrust <S> :yes related : <S> How does a turboprop engine keep running during thrust reversal?
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However thermodynamically it is more efficient to accelerate a greater mass of air slower, so turboprops are more efficient and that translates into lower fuel burn.
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Is optimal landing flare related to ground effect? Based on other questions it appears that a "flare" is always part of a healthy airplane landing . This question asked when a flare should be started, and I found it interesting that the accepted answer expressed it in terms of altitude. Which got me wondering: Is the need for a flare a consequence of ground effect? And the optimal flare height for a particular airplane a function of when it enters ground effect? <Q> It depends on the type of landing. <S> If you are doing a normal landing on a normal runway, the round-out and flare are required steps to put you in a position to be in level-ish flight just above the runway (the roundout), and controlling the touchdown by trading inertial energy for increased lift by pitching as you feel for the surface (the flare). <S> Ground effect has an effect on the flare phase by giving you more energy margin if the ground effect is strong. <S> So a low wing airplane with large flaps with a strong ground effect will have a lot more support from ground effect than a high wing airplane with small flaps that has weaker support from ground effect. <S> If ground effect wasn't there, it wouldn't really change how you land too much, except you may tend to carry power into the landing more, or arrive with a bit more energy by increasing the approach speed a bit. <S> In some airplanes the ground effect is much more pronounced than others (they like to float). <S> There are landings where you don't really flare at all. <S> In an extreme STOL approach, you fly to the surface already in the landing attitude, controlling descent rate with power and maybe little pitch adjustments only as required for speed corrections. <S> If the engine quits during such an approach close to the ground you are out of energy, already "flared" and will land hard and you live with that risk if you're doing that sort of thing. <S> And of course, there is no flare in aircraft carrier landings. <S> You fly a constant descent into the ocean, and the carrier's deck just gets in the way of your descent. <A> Yes , optimal flare is related to the ground effect (i.e. must take it into account), but is not a 'consequence' of it. <S> In a way, it's the opposite. <S> Flare does two things: primarily, it arrests your sink rate for a gentle touchdown, and also sets a correct attitude. <S> If the airplane has a particularly strong ground effect, this effect will reduce your sink rate and 'cushion' your landing, without you doing much. <S> There may be secondary effects though, which will require you to actively control attitude (pitch). <S> A case in point is Concorde. <S> Due to its wide-chord wing and high angle of attack on approach, it had a very strong ground effect. <S> So much so that it didn't require flare at all. <S> However, this ground effect produced a strong pitch-down moment, which required the pilot to pull the yoke in order to maintain the attitude. <S> As a result, the landing felt somewhat 'normal' for the pilot, except that the aircraft didn't pitch up and landed in the approach attitude. <A> For tricycle gear airplanes, this is typically a nose high attitude so it will make contact with the runway on its main landing gear only. <S> Critical to a good flare is arriving at the entry at the proper approach airspeed to minimize the float prior to settling onto the runway, typically Vref = 1.3*Vso + gust factor. <S> This provides just enough energy accomplish your two flare tasks prior to the airplane being exhausted of energy and settling down onto the runway. <S> Ground effect will amplify the time and distance covered during the round-out if the approach speeds are not correct, since it is reducing induced drag on the airframe, requiring longer times to exhaust the airplane of energy prior to touchdown. <S> The optimum height to begin the roundout depends upon the airplane in question, it’s approach speed, handling characteristics, etc. <S> Typically small GA aircraft will begin this process at about 10-12 ft above the runway. <S> Large transport category aircraft will begin this about 20-30 ft AGL. <S> Just prior to touchdown the airplane will be approx 1-2 ft above the ground and in the proper landing attitude, if the flare was accomplished properly.
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The flare, or roundout, is performed as a part of landing in order to accomplish two things: 1) Arrest the rate of descent on the approach and 2) place the aircraft in the proper attitude for it to gently touch down on its landing gear.
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How do propeller planes sync their propellers? While reading this question, I found that the answers did not address the point I had come for. On planes with electronic propeller synchronization, how is it actually accomplished? I know why propeller synchronization is useful but I am curious about the mechanisms behind how it works. <Q> I fly a large 4-engine turboprop. <S> It uses constant speed hydraulic props, which automatically change blade angle to maintain 1020 rpm. <S> The sync box (which I was unable to find a picture of) takes inputs from each engine's tachometer generator (where it gets the RPM signal) and a pulse generator, which is a magnetic pickup right behind the prop. <S> There is a magnet on the number 1 blade of each prop. <S> With this information, the solid state logic components inside the sync box can slightly change blade angle by sending power to the speed derivative servomotor. <S> This is different from the answer that @davidinnes provided, but I suspect that he's correct for the type of propellers <S> he's familiar with. <S> It works faster than the hydromechanical system and lessens RPM overshoots and undershoots as the prop works to get back to 100% rpm. <S> In this picture you can see syncrophasing in action. <S> The props are all slightly out of phase with each other, which reduces noise and vibration. <S> #2 and 4 look pretty close, but it's far from a perfect system. <S> You can definitely tell the difference from the cockpit when it's working well. <S> Again as @davidinnes mentioned, you can adjust the system to the change where the point of minimum (or maximum) noise is in the cabin. <S> We call it "running the buzz" up and down the tube, and it's a great way to annoy a navigator that you don't like <A> By modulating the fuel flow to the slave engine, ie the one which is to synchronise to the "master" engine, Note. <S> Limited authority of fuel modulation and not permitted in Take off or approach. <S> One writer alluded to synchrophasing to not only reduce beating bit alos reduce noise <S> , You can as I have done move the point of minimum noise around/along the cabin by small changes in phase angle. <S> Actual angle (relative position of the prop blades) depends on number of blades per engine, Easy with two engines, more than 2 ,,, its more of an art <A> I've been told that the flight engineer's position in a B-17 was such that he could look out a window and shine a strobe light at the prop blades on one side of the plane. <S> The strobe was slaved to one of the engines and the engineer could use the strobe light to tweak all the other engines into sync manually.
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The sync system on the P-3 also takes inputs through a potentiometer attached to the power levers, and can start increasing or decreasing blade angles if you change your power setting quickly.
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Are there any aircraft with a 4-wheel nose landing gear and a 16-wheel main landing gear? Are there any aircraft with a 4-wheel nose landing gear and a 16-wheel main landing gear? I need this to answer my review of an aircraft design project. <Q> this one has a better view of the wheels, but it's a CGI: <S> 4-wheel nose gear is rare, 16-wheel mains are more common: <S> Boeing 747 (4 trucks with 4 wheels each in 2x2 config), Avro Vulcan (main trucks with 2 axles with 4 wheels each), HP Victor (same as Vulcan), Shorts Belfast (same as Vulcan). <A> The Antonov AN-124 has 4 nose wheels and 20 mains which is close to that configuration . <S> The Antonov AN-225 is also close to being configured this way. <S> It has 4 nose wheels but has 32 mains. <S> ( source ) <A> I'd like to mention the Lockheed C-5 Galaxy , which has 4 nose wheels and 24 mains. <S> [source] <S> The large Antonovs use two two-wheel bogies for their nose gear, whereas the C-5 uses one four-wheel bogey. <S> For the mains, the Antonovs have multiple inline two-wheel bogies, whereas the C-5 has four six-wheel bogies. <S> As Moo commented while I was writing this, those distinctive six-wheel bogies can be deceptive from some angles and give the appearance of 16 main wheels.
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The Il-76: 4 main bogies with 4 wheels each, nose gear with 4 wheels.
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What are these beams sticking out of the Su-17's nose? As visible in the image above, there are these 2 beams sticking out of the Su-17's nose. One is longer and one is shorter. What are the purpose of these beams and exactly what do they do? <Q> conical nose reminded of its predecessor as much as the MiG-21, and ended with two long poles, one of which contained the very classic Pitot tube and the second a fire control calculator. <S> Source : <S> https://www.avionslegendaires.net/avion-militaire/sukhoi-su-17-20-22-fitter/ <S> Two protuberances extended the nose: a Pitot tube and above all a pole supplying measurements to an ASP-5ND fire control system Source: https://aviationsmilitaires.net/v3/kb/aircraft/show/2208/sukhoi-su-17-otan-fitter <A> Here you can see them covered while on the ground to prevent contamination: And here is a similar system on another aircraft from the same manufacturer, the Su-25: <A> Those are pitot tubes , used for measuring airspeed. <S> Two pitot tubes were used for backup purposes in case one forms ice or blocks for any reason (A380 has three). <S> This tube configuration was introduced in Su-17M after moving them from right to the left. <S> An extract from source - <S> The Su-17M also featured a number of rearrangements and tweaks. <S> One distinctive change was to move the backup pitot tube to above the left side of the engine intake, giving the aircraft a "double-pronged" appearance. <S> The positioning of the backup probe on the right side of the nose had led to minor problems with stall characteristics. <S> The parachute fairing at the base of the tail was changed to a more streamlined configuration that accommodated a single cruciform parachute, while the antenna for the Sirena system was relocated from the tailtip to just above the parachute fairing. <S> The hydraulic system of the aircraft was completely redesigned, with a dual instead of triple system. <S> I'm not sure why one is shorter than the other though.
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Those are Pitot tubes , used to measure the dynamic pressure in front of the aircraft, from which the airspeed can be calculated.
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The NASA X-57 uses 12 electric motors for takeoff. Does it need 12 control levers or just one? If the NASA X-57 uses 12 motors for takeoff, does it need 12 controllers (like throttle levers), or just one? The traditional way of engine throttle design was 1 throttle per engine, but what if you have 12 engines? Twelve levers would be unmanageable, pushing a quadrant of 12 levers forward on takeoff. I suppose that on initial setup, you would need a small dial for each prop to sync rpms. More sophisticated electronics could have a feedback loop to do this automatically. So... what about just 1 controller, and 2 or 3 backup controllers for redundancy as they are electronic and could easily be blown. I'm thinking of a 3 or 4 position selector switch to choose the active throttle, sort of like choosing between magneto 1 and magneto 2 in a typical GA aircraft. Yes, you could wire the motors up in banks of 4 and have a quadrant of 3 levers, but my specific question is: Would having just one active controllers for 12 motors be acceptable? <Q> The throttle in older airplanes directly controlled the air-fuel mixture allowed into the intake manifolds. <S> If electric motors were used, the throttles would have been attached to mechanical rheostats. <S> In the age of computer controlled engines/motors, this direct linkage is not necessary. <S> You would essentially just tell the computer how fast you would like to go. <S> The system will take care of the rest. <S> In most cases, the throttle is retained in the cockpit to provide the human pilot with a familiar interface with the computer. <S> Honestly, in an airplane, where throttle settings and changes are more stable and predictable, a knob or a couple of buttons would suffice. <S> FADEC controlled engines/motors are pretty standard now. <S> The method of inputting your desired controls in a fly-by-wire system is arbitrary. <S> It is just a matter of comfort level with the controls. <S> We might even get to the point of a true GUI cockpit one day. <S> This is not something that you would absolutely need. <S> But, it would be convenient. <S> Some very complicated aircraft like <S> the V-22 Osprey rely on the pilot not having direct control over the engine-prop systems. <S> It’s absolutely necessary for a computer system to coordinate the two engines during VTOL operation. <S> The same problem would present itself in a quad-copter large enough to carry human passengers. <S> As an aside, I vividly remember the first throttle-by-wire car our family ever owned. <S> It was a Hyundai Santa Fe. <S> Though, not difficult to drive. <S> The throttle response took some getting used to. <S> Also, modern electric cars with multiple motors have only one throttle. <A> what about just 1 throttle, and 2 or 3 backup throttles for redundancy as they are electronic and could easily be blown <S> You wouldn't need separate levers for that: just have one lever driving two or more throttle position sensors. <S> You might want separate levers for the left-side and right-side engines, so you can use differential throttle control to steer the aircraft in an emergency. <A> For a system with so many electric motors, there is an interface that converts what the pilot wants to what those motors need to accomplish to deliver it. <S> Something similar is also seen in some cars' suspensions and aerodynamics (working in tandem to keep the car under control when an inexperienced driver pushes it beyond his or her skills), and even throttle control. <S> With that said, an issue with that is what I call the "Eclipse Problem" after the throttle issues caused by the FADEC in the Eclipse 500 . <S> Main issue is not the FADEC by itself but that the Eclipse has no backup throttle control as it was designed originally to be but a testing platform for the engines. <S> And then someone bought the design and made a general aviation plane out of it.
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In the case of a multi-engine electric airplane, you would want at least two controls to account for differential thrust when desired. The need for throttles is to provide a linkage to the carburetor/throttle body in the age when everything was mechanical.
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How are turboprops and other propeller planes pressurized? I know how most turbofan jets are pressurized: But it can't be the same with turboprops, as I don't understand how propellers can take in the air. Yet, planes like Q400s can fly above 8000', all the way up and higher than FL220! Can somebody explain how this is possible? <Q> Turboprops are actually turbine engines. <S> They can produce bleed air just like turbine engines (e.g. turbofan). <S> The bleed air can be used directly to pressurize the cabin, or it can drive another turbo compressor to pressurize fresh air from the outside: Modern aircraft with supercharged piston engines simply use bleed air from a) the main engine's compressor or b) the main engine's turbo charger <S> Another solution is to drive dedicated air compressors to pressurize the cabin. <S> Typically this may be Roots blowers or centrifugal fans. <S> They are mechanically driven from the main engine(s). <S> Image source and more information on this topic: www.aircraftsystemstech.com <A> A turboprop and turbofan are not that different actually. <S> You have a turbine engine core that powers the big fan at the front or the big propeller via a gearbox (although the turbofan still gets some of its thrust from the engine core, but the turboprop does not): <S> ( image source ) <S> On the Dash-8 Q400 for example, the engines provide bleed air for pressurization: <S> The aeroplane is pressurized by engine bleed air supplied to and distributed by the air-conditioning system. <S> Pressure is maintained and controlled by the cabin pressure control system which governs the rate of outflow from the pressurized areas (Figure 12.2-10) of the aeroplane. <S> An aft outflow valve primarly controls the outflow of air, and is assisted by two safety valves. <S> ( Dash-8 Q400 FCOM - Air Conditioning and Pressurization 12.2.2.1) <S> Air entering at the engine inlet is directed rearard and compressed (Figure 12.23-1). <S> Two compressors carry out compression for combustion and bleed extraction purposes. <S> Air is first ducted to the low-pressure (NL) axial compressor and then to the high pressure (NH) <S> centrifical compressor where it undergoes a seconds stage of compression. <S> ( Dash-8 Q400 FCOM - Power Plant 12.23.3.1) <S> The following image shows the bleed port in the PW150A engine as used on the Dash-8 Q400: ( image source ) <A> I was a P-3 Flight Engineer and the Allison T-56 engines had engine driven compressor's mounted on the propeller gearboxes on the inboard engines that allowed for a 30'000 ft. Ceiling. <A> Piston powered aircraft can also be pressurized, the models that are have turbo-superchargers, an exhaust driven turbine that pressurises the air going into the cylinders. <S> Some of the air from the turbos goes to the passenger cabin. <S> The level of pressure is controlled by outflow valves just like jet powered aircraft.
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A turboprop plane can be pressurized in the same way a turbofan plane can: via bleed air from the compressor stage of the turbine engine.
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Can anybody give an example about Clearance Expiry Time? Clearance content is included: callsign, flight path, clearance border(destination aerodrome, available report point, controlled airspace border), flight level along the route or for a specific part of the route, etc. and end time of clearance or clearance expiry time . Can you give an example of a clearance expiry time? How does it end, is there any specific time that is notified by air traffic controller to pilot to pass some specific point? How is it said? can you give me a clearance example? <Q> This is most commonly seen when starting your flight plan from a pilot controlled airfield. <S> You can not start your IFR flight plan until you are in controlled airspace. <S> At a controlled airfield, you would have to “hold <S> /wait for release”. <S> You can not leave the ground one second past that time unless you call ATC for a new time. <S> If you do not leave the ground, you must contact ATC <S> ASAP.This is mainly an issue at fields where radio reception between ATC and aircraft at that field is spotty or nonexistent. <S> You are to then follow your clearance instructions into controlled airspace. <S> Once you are within both radio reception and controlled airspace, you must either contact ATC, land as soon as practicable within Class G, E, or D (with clearance) airspace, or follow the Radio Inoperative procedures outlined in FAR 91.185. <S> Contact ATC immediately upon landing. <S> You can not deviate from this. <S> Remember, IFR can only be flown in controlled (A,B,C,D or E) airspace. <S> Only there can ATC provide the required separation necessary for IFR flight. <S> Although VFR Flight Following follows similar rules, VFR Flight Plans do not. <S> Do not mistake this for the Expect Further Clearance time that you would get in flight. <A> The current version of the AIM says: Clearance Void Times: <S> A pilot may receive a clearance, when operating from an airport without a control tower, which contains a provision for the clearance to be void if not airborne by a specific time. <S> A pilot who does not depart prior to the clearance void time must advise ATC as soon as possible of their intentions. <S> ATC will normally advise the pilot of the time allotted to notify ATC that the aircraft did not depart prior to the clearance void time. <S> This time cannot exceed 30 minutes. <S> Failure of an aircraft to contact ATC within 30 minutes after the clearance void time will result in the aircraft being considered overdue and search and rescue procedures initiated. <S> EXAMPLE− Clearance void if not off by (clearance void time) <S> and, if required, if not off by (clearance void time) advise (facility) not later than (time) of intentions. <S> Let's say you're using a GCO or telephone to contact an ARTCC for your clearance out in a low-population area with little infrastructure making it impossible to contact ATC from the ground via standard radio equipment. <S> After you receive your clearance, you will hang up the call or change frequencies and break contact with ATC. <S> Due to the break in communication, they will end your IFR clearance by assigning a void time in case you don't get airborne as soon as expected. <S> If you delay beyond your void time, you would need to call and get a new clearance that you would expect to have issued with a new void time. <S> The void time is short enough that the implied intention is for the aircraft to receive the clearance while stopped at the runway's hold short line already prepared for takeoff. <A> Clearance expire times are very common in non-radar environments such as on Oceanic Tracks. <S> ”CLIMB TO REACH <S> FL370 <S> BY 1325Z, REPORT LEVEL”
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At an uncontrolled airfield, you would have from the time of activation until the end time of clearance or clearance expiry time to takeoff and have wheels up.
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Which is more efficient: a jet engine or a rocket-powered engine? Knowing that rocket powered engines have higher speeds than jet engines, it raises the question: are jet engines more efficient than rocket powered engines? This is of course in terms of fuel consumption per distance traveled, as I am curious whether a rocket engine allows an airplane to travel a distance more quickly compared to a jet engine when consuming the same amount of fuel. <Q> Jet engines are far more efficient. <S> The metric to compare them is ' Thrust-specific fuel consumption ', i.e. the amount of fuel used to produce one unit of thrust. <S> Fuel consumption per distance traveled is proportional to this. <S> A few figures from that page: Rocket engine: Space Shuttle main engine, 225 g <S> /kN.s <S> Jet engine in afterburner: <S> EJ-200: 48 g/kN.s <S> Jet engine, dry: <S> CF-6: <S> 17 g <S> /kN.s <S> So a rocket uses ~10 times as much fuel to produce the same thrust. <S> During and after World War 2, there was some interest in rocket-engined aircraft. <S> The Me-163 saw service in the Luftwaffe. <S> The interest continued for a decade or so, until jet engines with afterburners were developed. <S> One exponent of that interest was the Saunders-Roe SR-53 , a short-range interceptor with both a jet engine and a rocket. <S> It was developed in response to an RAF requirement for an aircraft that could take off and get to high altitudes very quickly; more quickly than could be attained with the jet engines of the day. <S> Jet: <S> Armstrong Siddeley Viper, 1640 lb thrust. <S> Rocket: De Havilland Spectre, 8000 lb thrust. <S> Fuel carried: jet: 500 lbs rocket: 10,500 lbs <S> Endurance: <S> jet: 45 minutes rocket: up to 7 minutes <S> speed: <S> jet: 180 kts rocket: accelerate to Mach 2 once <S> , then the fuel ran out (source: mostly 'British experimental jet aircraft', Barrie Hygate.) <S> It was superseded by the EE. <S> Lightning , which had 2 afterburning jets. <S> It had 4 times the range despite carrying less fuel and more payload. <A> The key to why an air-breathing jet engine is "more efficient" is that it doesn't need to carry oxidizer, it can just use the atmosphere. <S> Carrying oxidizer is very heavy, which will severely impact the range and speed of the aircraft. <A> "Ballpark" figures for an 8000 mile trip Atlas ICBM vs 747 jet airliner: Atlas ICBM: 8000 lbs delivered using 75 tons of RP-1/225 tons LOX = 27 lbs/ton total propellant, or 108 lbs/ton on a hydrocarbon fuel basis. <S> 747 airliner: 150,000 lbs passengers and luggage using 150 tons fuel = 1000 lbs/ton and a softer landing. <S> Biggest disadvantage of the rocket is having to carry it own oxidizer, as 1 lb kerosene requires more than 3 lbs of oxygen for combustion. <S> Not using a wing also greatly reduces efficiency. <S> The winged jet is around 40 times more efficient for this application.
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Even if you add afterburning, a jet is more efficient.
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Is it possible to use US-made engines in Russian made air-frames? Suppose, someone buys 300 Pratt & Whitney engines from the USA and 150 Mig-35 air frames from Russia. Then, they use their in-house expertise to fit those engines to those air-frames. What challenges would have to be faced by the user? <Q> Or on some occasions, the airframe is first licensed or reverse engineered, after which, experience and expertise is gained to enable the re-engine effort. <S> China is notable in this area due their Russian lineage of airframes and a long lasting desire for western engines, and a mixed relationship with both. <S> India is in a similar position <S> but I'm not aware of any such attempts. <S> Notable examples: Y-8-F600(Antonov An-12 clone) with PW engine , failed Sabre II(Mig-21 derivative) with GE or PW engines ), failed. <S> Shenyang J-11(license production Su-27 derivative) with Shenyang WS-10 engine (reverse engineered CFM56 derivative) , successful. <A> We're not on law.stackexchange.com, but from what I can tell, the legal consequences would be limited to losing some benefits from warranty/support agreements. <S> There is no reason to do this. <S> The engines on modern Russian fighters are quite good and among their selling points. <S> You'd be concerned with upgrading their avionics - which are, of course, one of the most tightly-controlled export items - not their already excellent flying qualities. <S> This is not possible. <S> For airliners or other pylon-engine configuration aircraft, re-engining is easy. <S> For fighters with internal engines, it's not. <S> The airframe is built around the engines, with special ring frames that allow room for the engine while carrying through the wing loads. <S> The engines are not geometrically compatible. <S> None of P&W turbofans that could suffice to power a MiG-35 would fit in it. <S> TL;DR version: <S> To paraphrase the old joke, you want a fighter that flies like a Flanker, sneaks like a Raptor, shoots like a Rafale, and maintains like a Gripen... not the other way around. <S> The MiG-35 is Russia's "low" component, similar to the F-16 in the US arsenal - lower cost, lower maintenance, high but not best achievable performance, and in its case also good improvised airfield capability. <S> As part of that, it's a mid-size airframe, with smaller than average engines, optimized for efficiency and durability. <S> However, it's not the best possible engine for the MiG-35. <S> The latest version of its own engine , the VK-10M, offers more thrust than the GE-414, has vectored thrust versions, and is a perfect fit for the frame. <S> If you want the best, you'd want a custom engine, like an enlarged higher-bypass version of <S> the EJ-200 (that's doable). <S> But, then, if you want the very best, you'd probably start with the Su-35 or the F-35. <S> The MiG-35 is a workhorse. <A> If the question is not limited to specific airframes, the Irkut MC21 airliner is planned to have two engine options : Pratt & Whitney <S> PW1400G (American) and Aviadvigatel <S> PD-14 (Russian). <S> So the answer is <S> Yes, if you include airliners; you can even order them from the factory that way. <S> First deliveries were scheduled for this year : I suppose that may be subject to change. <S> (there were also plans to give the Sukhoi Superjet a P&W engine option; these seem to have fallen by the wayside at the moment)
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Re-engine an existing airframe is such a complex undertaking, in a way that so much R&D is required that the entire aircraft ends up being reverse engineered to make it work. The only US-built engine that could both fit and power the MiG-35 is the GE-414, after some modifications.
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Does the FAA generally consider a door opening in an unpressurized cabin during flight to be an emergency? Sometimes doors pop open on older training aircraft during flight. I've read some indications from poorly-documented sources suggesting that this is considered an emergency, but it doesn't appear to be addressed in any flight manuals, the AIM, or the FARs. Is there any publication from the FAA that indicates a stance on the issue as it pertains to it being considered an emergency or not? <Q> A door popping open is not an emergency in itself, it has to cause a threat to the safety of the flight or those on the ground to be an emergency. <S> I've had doors pop open in a light aircraft in flight and it has been a non-event every time, I didn't mention it to ATC as there was no reason to <S> , I just told maintenance once I was on the ground. <S> Regs generally don't get that specific, what is life threatening on one airplane may be a non-event in another. <S> The POH and airplane specific training is typically where emergency events are specified. <A> A door popping open in a GA aircraft is not considered an emergency. <S> I have not seen it in the FAR/AIM. <S> I don’t have a POH in front of me. <S> If memory serves me correctly, the POH for a 2015 and later Piper Archer has this event listed under the category of Abnormal Procedures. <S> There is a separate category for Emergency Procedures. <S> Although the checklists are less than official documents confirming this event’s status, they definitely point to it not being an emergency. <S> Like the previous poster, I have had doors open during flight. <S> It has always been a non-event. <S> The doors tend to be designed with the hinges positioned on the leading edge of the door. <S> This keeps the door from flying fully open in the aircraft’s slipstreams. <S> One instructor actually demonstrated the effects of alternately opening the doors on a Cessna 172 to induce yaw. <S> You have to apply a considerable bit of force to swing the door fully open at 90 knots. <S> Conversely, only half of the Robinson and Loach helicopters I have flown have had the removable doors in place. <S> And, most of the smaller skydiving planes in which I have flown have been unmodified, regular GA planes with the seats removed. <S> Some of them had the right door removed, also, and were still able to achieve 17,000 feet. <A> It really depends on the aircraft. <S> In most certified light piston training aircraft <S> it's a non-event as described in other answers. <S> In the Lancair 320/360 and Legacy which have forward-hinged canopies instead of side doors, and have much higher wing / tail loading than the typical trainers, it can be quite deadly. <S> Beyond the pilot distraction factor, the aircraft becomes difficult to control due to the disrupted airflow over the tail and oscillations of the canopy angle, forward visibility is substantially reduced, and the pilot has to take some actions that are not necessarily intuitive ( increase speed, do not try to land immediately, do not try to close the canopy, go to altitude to practice handling, then go to a very long runway and touch down at much higher speed than normal). <S> https://www.lancairowners.com/sites/www.lancairowners.com/files/wp-content/uploads/Legacy-Canopy-Safety-Issue-27-April-2014.pdf <S> I'm not sure whether a certified aircraft with a similar characteristic would be approved; perhaps with a reliable warming system to prevent takeoff with the canopy improperly latched.
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Opening the door (or in some cases, the tail) does not seem to adversely affect performance enough to classify it as an emergency. I've never seen a FAA or other country authority publication saying it was an emergency. On the checklists for three different aircraft models from my former flight school, it was also listed under Abnormal.
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Is it possible to have an angle of incidence for a vertical stabilizer? horizontal surfaces in airplane have small angle of incidence in general, Is it possible to have an angle of incidence for a vertical stabilizer?Please help me to find it. Thanks!! <Q> Some vertical stabilizers will have a slight angle of incidence to counter left turning tendencies. <S> Older model Cessna 172s and 150/2s have <S> a little metal trim tab that can only be adjusted by manually bending it from the outside. <S> This will serve to adjust the vertical airfoil chord line angle in the aircraft slipstream or relative wind. <S> The degree of incidence will be manufacturer and model specific. <A> Yes, but the term "incidence" normally only applies to horizontal surfaces. <S> With a fin it's usually called "fin offset" and is very common on single engine tractor aircraft. <S> The offset helps align the fin into the spiraling airstream coming off the prop so that a counteracting rudder input isn't required (or at least a smaller input is required) to counteract the offset slipstream trying to push the tail to the side. <S> It's usually 2 or 3 degrees to the left for an engine turning clockwise from the cockpit where the flow at the fin leading edge is coming from the left, or to the right for an engine that turns counterclockwise. <S> It's very common but not universal. <S> Some airplanes just use a fixed trim tab on the rudder to passively do the same thing, or both a tab and an offset fin. <S> They also often have the engine offset several degrees on the mount, to the right on a clockwise engine. <S> Look at single engine airplanes from above and it becomes quite apparent how the engine/prop is crooked as well as the fin being angled to the side, like the plane got into a fender bender accident and just drove off like that. <S> Makes you wonder how the dang things fly straight in the first place. <A> I'm no expert, but Wikipedia helps. <S> [source] Since the vertical stabiliser is on a different geometric plane, there can't be an angle of incidence as there is with the wings.
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The angle of incidence is the angle between the chord line and a reference line on the fuselage.
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Why don't ailerons affect pitch? Why don't ailerons affect pitch, or do they? I'm told spoilers can affect pitch if not placed in the right spot. On a classic standard wing configuration, why don't ailerons affect pitch as they are at the trailing edge and would create a moment around the spar which I'm told it usually located at 25% chordin ultralights. <Q> Two reasons: Because they don't have a very long moment arm. <A> This isn't specific to ultralights, but more generic to airplanes. <S> They could, but ailerons don't have the torque to change the direction of the aircraft like the elevators would. <S> The center of pitch change would be a line that goes through the aircraft similar to the position of the wings. <S> The elevators being further away from the center of the aircraft can push more. <S> Designers purposely only have the elevators move for this reason. <S> The ailerons move in opposite directions when the move to induce roll. <S> The center of roll would be roughly the center of the fuselage from head to tail. <S> The ailerons are positioned away from this point to increase their torque. <S> I hope this helps. <A> When de Havilland developed the first Cirrus-engined Moth in the mid 1920s, they included differential movement of the ailerons. <S> The common problem they faced was was that when turning and inadvertently approaching a stall, moving the inner aileron down to pull out of the turn would actually encourage tip stall at that moment. <S> So the aileron being lowered moved by only a small amount, while that being raised moved more authoritatively. <S> Overall this did create a small pitch-up moment but it was minimal and did not adversely affect handling. <S> de Havilland used it extensively afterwards, I don't know about other designers.
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Because their movement works in opposite directions to each other, any pitching moment one side might cause is cancelled out by a pitching moment going the other way from the aileron on the other wing.
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Do we need to know the true track to a VOR? An aircraft can lock onto the location of a VOR and we can see the QDM (magnetic bearing to the station) to the VOR. If this is the case, do we still need to know the true track of that route? And if so, why? By extension, if we essentially have all we need to get to the VOR in the aircraft, why do we need to know about QTE (true bearing from the station)? NB: I have no experience in flying a navigation flight <Q> Presuming of course that your airplane has a magnetic compass to fly that bearing, there is simply no reason to convert to true. <A> You don't get either and you don't need it. <S> The VOR signal gives you a radial to the station. <S> This is normally referenced to magnetic north, because that's what you have on board¹, but it might have been last aligned twenty years ago and so might be a couple of degrees off as the magnetic declination slowly changes over time. <S> It does not matter what it is anyway. <S> The instrument works so that you select the desired radial and it shows you how far (in degrees) you are to the left or right. <S> You align yourself roughly in reference to the magnetic compass and then you steer right if the needle is on the right or moving to the right too fast and steer left if the needle is on the left or moving left too fast, until you manage to centre the needle. <S> At that point your heading is something that depends on wind and the misalignment of the VOR. <S> But you know you are following the radial that defines whatever airway or procedure you are flying <S> and that's what you needed. <S> Note that when the VOR is re-aligned, all the charted procedures have to be updated to the new radials <S> , so they don't want to do it that often. <S> Having the radials off by a degree or two is not a problem, because the heading does not match the radial due to wind in practice anyway and updating all the maps is a lot of work. <S> ¹ <S> A gyrocompass is only self-aligning when moving slowly, so while they can be used on ships, on aircraft the heading indicator is always slaved to the magnetic compass. <S> You can now get true track from GPS, but then you don't really need VOR anyway. <S> VORs exist for aircraft that don't have GPS or their GPS failed. <A> The radials extending from the VOR are normally based on local magnetic variation (the compass rose around the VOR on the chart is angled off true by the amount of local variation so that the 360 deg Radial is pointing to the magnetic pole). <S> The VOR gives no bearing information relative to the airplane; it only tells you that you are somewhere along, or to one side of, a selected radial extending from the VOR, regardless of which direction the airplane is pointed. <S> But since the radial represents a magnetic track, you fly magnetic headings to orient yourself and and stay on the radial <S> you're on as you fly toward or away from the VOR. <S> Except.... if you are in the Canadian Arctic, in an area called the Northern Domestic Airspace (the Northwest Territories and Nunavut more or less), the compass is useless because the magnetic pole is right in the middle of it, and everything, airway tracks, runways, VOR compass roses (the few that are up there), are oriented to true. <S> In that case you fly true headings and tracks, and if you are tracking to the Cambridge Bay VOR , it's radials are also true, and heading information has to come from a directional gyro that is aligned to true heading, and your compass becomes a nice instrument panel ornament. <A> You do not need the true bearing to the station in order to navigate to it. <S> However, if you don't have a GPS or other NAV equipment on board, you need some way to estimate your groundspeed, and knowing the true bearing can help you do that. <S> Winds aloft forecasts are given with reference to true north, so if you know your own track relative to true north and your wind correction angle, you can deduce your groundspeed with it. <S> You can check this against your resulting calculation of time to the VOR station to confirm it. <S> All of this is important so that you don't run out of fuel. <S> Luckily, having a GPS on board, or even a DME, or even another VOR radio, will allow you to do redundant groundspeed calculations without all the math or winds aloft tables.
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The short answer is no, you don't need the true bearing to the station if you have magnetic bearing.
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When was the first THS (Trimmable horizontal stabilizer) used and on what aircraft? When was the first THS (Trimmable horizontal stabilizer) used and on what aircraft? Has any UL or GA trimmable stabilizer? <Q> If the question is understood to encompass any form of horizontal stabilizer which may be adjusted in flight (with or without a separate movable elevator), then the answer would appear to be Sir George Cayley's 1849 full-sized glider which briefly took flight-- see http://www.flyingmachines.org/cayl.html . <S> The Wright brothers also used all-moving horizontal surfaces on their early gliders and airplanes, but located in front, as canards. <S> However, a comment has clarified that the question is meant to only encompass a horizontal stabilizer which may be adjusted for trimming the aircraft, with an attached elevator for pitch control inputs. <S> Naturally, all these aircraft featured an elevator attached to the adjustable horizontal stabilizer. <S> The same source says that many old Waco biplanes used the same feature. <S> In this photo of a 1936 Waco biplane , the slot associated with the adjustable horizontal stabilizer is clearly visible. <A> It would appear to be the Boeing 707/720 , followed by the DC-8. <S> Lots of GA airplanes derive pitch trim and static stability from the stab surface, that is operated manually by a screw jack driven by the trim wheel, and only use elevator for maneuvering inputs (having no trim tab, it just trails when hands off). <S> Significant ones that come to mind are the Cessna 180 /85 family, the Piper Cub /Super <S> Cub/Pawnee family, and the Mooney M20 family. <S> Modern airliners with trimmable stabs and hydraulic controls use a particular geometry in the elevator control linkage (or by software if FBW) at the control linkage interface between the horizontal stab and and vertical stab that always keeps the elevator actuator linkage neutral position aligned with the stabilizer chord line, so the surfaces are always hydraulically maintained in stab chord alignment in the absence of a control input. <S> The result is the trimmable surface becomes the entire stab/elevator unit, not just the stabilizer. <S> As well the control stick neutral position in the cockpit <S> never changes, which takes getting used to when transitioning from an airplane with a elevator tab for trim, where the elevator stick position changes with trim. <A> It was first used on Spitfire in October/November 1944 to test out the idea, and was then to be used on the 1943-designed Miles M52. <S> The M52 was going to be a jet-powered supersonic aircraft and would have been the world's first supersonic aircraft. <S> It's not well-known because the design was given to Bell as they started design of the rocket -powered X-1, followed by the British government cancelling the project.
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According to page 9 of the book "Aces Wild" by Al Blackburn ( see this Googlebooks link ), the first use of an in-flight-adjustable horizontal stabilizer was in 1929 by Clarence Gilbert Taylor in his B-2 "Chummy", which eventually evolved into the Taylor Cub and then the Piper Cub, all of which used the same stabilizer trim system.
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Is there a more specific term than 'flight line' for straight lines flown during flight? I work for a small software startup, where its just my boss and I. Prior to this job, I had no experience with aircraft. We have a client that uses our software to fly a pattern over an area, where they fly straight for a while, turn around, and fly back over an adjacent area. They do this so that they can canvas an entire area. I sketched out what this looks like below. (start) ---------------------> (turn around) )(turn around) <--------------------- ( ---------------------> (turn around) )(turn around) <--------------------- ( ------------> (and so on) My boss refers to one of these straight flights as a "flight line". When I looked up the term "flight line" though, I found that it has a few different meanings all related to where the aircraft is parked or serviced on the ground. So my question: Is there a more correct term than "flight line" that describes the patterns our client flies, which are these sets of straight lines? <Q> Although my aviation knowledge is not all encompassing, I would argue that you, your boss, and your software company may want to know your audience as well as possible. <S> The same terminology can mean different things to different segments of society. <S> For instance, uncontrolled airspace/airfield would mean something totally different to a pilot than it would mean to the media or general public. <S> A quick search of the Federal Aviation Regulations/Airmen’s Information Manual, the Pilots Handbook of Aeronautical Knowledge , and the Airplane Flying Handbook <S> only garners results describing specific areas of an airfield and the personnel working there. <S> My experience in civilian aviation and in the military is consistent with this usage. <S> Great circle route Flight path <S> Leg <S> Direct leg <S> Course <S> Direct course <S> Track <S> The term you are probably looking for is Transect pattern consisting of transect lines. <S> Someone more knowledgeable might have a better term. <A> The correct term is a Route Segment. <S> CFR 14 part 1 describes a Route Segment as a portion of a route bounded on each end by a fix or navigation aid (NAVAID). <S> If the flight is in a straight line from one point to the next, it is said to be "Direct". <S> From a common usage standpoint, DJClayworth is correct in that a "leg" is used to describe a section of a route. <S> However, a leg may contain multiple waypoints or, from a commercial operator's standpoint, an entire flight between airports. <S> I am unaware of a standard aviation term for the multiple parallel segments, but as the operation in a type of survey, I think Dan F.'s "transect" description is appropriate. <S> The term "Flight Line" is only used, to my knowledge, to refer to the parking and servicing portion of the airfield apron. <S> The term "Flying the Line" is often used to describe a pilot or crew which is actively and frequently scheduled to fly the unit's or company's sorties. <S> Hope <S> this helps. <S> (Current Active Duty USAF pilot flying for 20 years) <S> Addition - I have worked with units and contractors whose mission was ground mapping and sensing using airborne LIDAR (Light Distance and Ranging). <S> Their sortie profiles were very similar to the one you described. <S> The USDA published guidance for data collection from aerial LIDAR platforms ( https://www.fs.fed.us/pnw/pubs/pnw_gtr768.pdf ). <S> I have posted their graphic with their names for the various patterns. <A> In the world of idealized navigation, a journey consists of flying a straight line from your departure point to another location, making a turn and flying a straight line to a different point, and so on until you reach the point that is your destination. <S> Reality is a bit more complicated, but it's a useful approximation. <S> The points are called "waypoints" and the straight lines are called "legs". <S> Although your flight path is a bit different from this, the term "leg" might well apply. <A> Both terms are essentially interchangeable, and are often modified to “ground track” and “true/magnetic course” for clarity. <A> From the description of your situation, I would call the entire pattern a "grid sweep" and reffer to each line as a "grid <S> line". <S> Gotta mention <S> I have nothing to do with aviation :) <A> I have little knowledge of aviation but the idea reminds me of scanlines as they are used in computer graphics as described here: <S> https://en.wikipedia.org/wiki/Scanline_rendering Maybe scanline is a more appropriate term.
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Without delving into too much detail, the most appropriate pilot terms for the straight legs of the search grid you describe would be “track”, or “course”. When pilots, ATC, and others in the aviation field describe an aircrafts path, they use terms such as the following: Route Return route Round-robin route
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How do pilots travel from remote private airports after landing? What if you fly your own personal plane to a small private airport in the countryside that has no public transportation? I imagine that most pilots don't have a car parked at each private airport they intend on flying to. That is, of course, unless your car is small enough to fit inside your plane. If you want to go somewhere twenty miles from the airport, for example, do you just call a taxi or ask a friend in that town to pick you up in their car? <Q> You do whatever you can. <S> Sometimes you call a taxi/Uber <S> , sometimes you walk, sometimes you pack a small folding bicycle into your plane, and sometimes you borrow the airport car. <S> It's usually a scary rusted out pile of junk, but it works. <S> If you borrow it you're expected to return it promptly & with a full tank of gas. <S> It's wise to make arrangements for ground transportation before you arrive - <S> there's no guarantee that any particular option (except walking) is going to be convenient and available. <A> In my experience, in the United States, most General Aviation airports, GA sections of the airport, and Fixed Based Operators have one to a fleet of courtesy crew cars. <S> If you are a pilot being serviced by that particular facility, you are given access to a crew car. <S> The length of time you can use the car can be anywhere from one to four hours, depending on the facility. <S> The type of car can greatly vary as well. <S> I have borrowed cars as nice as brand new Infiniti sedans, Chevy Suburbans, Tahoes, Toyota Camrys and Corollas to as crappy as the POS pictured below. <S> Even at unattended airfields, there may be a car pilots can access through the local police department. <S> Check out the following... <S> CODE OF THE COURTESY CAR COURTESY CAR FINDER <S> FBO COURTESY <S> CARS <S> The best GA FBOs have even greater facilities than just a car. <S> Many have crew-rest rooms, small theaters, meeting/briefing rooms, full crew kitchens, airport golf carts, and shower facilities. <S> Some even have arraignments with local restaurants for them to provide transportation to and from the restaurant in nicer cars. <S> Same with local hotels. <S> The Class Bravo, Charlie and busier Class Delta Airports will have rental car agencies located in the FBO for overnight rentals. <S> There are many apps and websites that give details of the amenities available at each participating FBO. <S> ForeFlight is one of them that does an exceptional job. <S> The original poster is assuming that the majority of general aviation airports are accessed by public transportation. <S> In the United States, there are even major Class Bravo airports without a substantial public transportation system. <S> And, the systems that are there are predominantly not used as opposed to shuttles, taxis, and rideshare services. <S> Unfortunately, the GA portions of the airports are located away from the commercial terminals. <S> Therefore, there is not usually access to public transportation except for prearranged shuttles, taxis, and rideshare services. <S> No A/C and windows that were off their manual (not power) <S> tracks...in Texas...in August. <S> But, we were thankful to have it so that we could run into town to get a bite to eat. <A> A pilot I know used to own a folding motorcycle for such purposes; when stowed it was about the size/weight of a large suitcase <S> and I'm fairly sure (this was 30 years ago) <S> it would fit through the luggage hatch of his Cessna 172. <S> It could carry two people but at 49cc, and a two stroke engine at that, it was certainly a leisurely and perhaps fragrant way to travel. <S> Being classed as a small motorcycle/moped there were a different set of licensing rules applicable that meant one didn't have to have the class of driving license as would be required for a larger engine <S> On occasions where there was a need to transport more people they were usually going to a place where one person could use it to retrieve a larger vehicle from somewhere at the destination, though a couple of times there was a bit of shuttling to do, one pillion passenger at a time <S> It seems they're still around and look to have modern, luxury facilities, such as lights and mud flaps, compared to the one I remember: <A> Typically the FBO's courtesy car is used, but I've flown into a lot of airports that either do not have an FBO (or the FBO does not have a courtesy car), or it was after hours <S> and no one was around. <S> Sometimes you might not even have cellular service in the remote airports and they won't have a landline phone in a public area. <S> That's when you either start hiking or <S> you are glad you brought a bike along with you. <S> At my age, I'm not going to be doing much hiking... <S> Even walking from one end of the runway to the other is going to kill my old knees. <S> I can still ride a bike though and it will fit in the back of my plane. <S> I fly a 4-seater, but no one ever occupies the other 3 seats, so I have room to put a bike. <S> I have put 2 full size bikes in there once when my wife flew with me. <S> I think I had to remove the front wheels though. <S> These days though, with the electric scooters and such, that might be an option for some people. <S> Back before Hurricane Katrina, I was over at Lakefront airport in New Orleans and the FBO courtesy cars that they had at the FBO which had the military fueling contract <S> were late model Jaguars. <S> Sure, they were the 6-cylinder engines and this was when Ford owned Jag <S> , so really they were just an overpriced Ford with a Jag nameplate, but that's still a lot more than you saw at other FBOs.
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Many small airports in the US have a car (often a retired police car) available for itinerant pilots to borrow.
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Am I Required to Use the Runway Advised by a Unicom? Let's say that an uncontrolled airport's ASOS reports wind 060 @ 6 knots. The airport's unicom advisory states that Runway 22 is in use. Am I required to use Runway 22, or can I use Runway 4? <Q> You are not required, but it is advisable if there are other aircraft in the pattern. <S> My home airport often does not have anyone in the pattern and pilots that are based there will sometimes land opposite of the advised runway because their hangars are located at the other end of the runway from the FBO. <S> This means that they can either land long or do a long rollout after landing and then turn off at their hangars. <S> If they landed on the advised runway, they would having to taxi all the way back down from the FBO end of the airport or applying brakes to try to make one of the turnoffs to the taxiway. <S> You just listen on the CTAF and announce your intentions if you don't hear anyone. <S> It is probably more used when a pilot is flying back and wants to just make a long straight in approach while also ending up at his hangar with minimal wait time. <A> At uncontrolled airports landing is entirely at the pilots discretion, that includes which runway you use. <S> Advisories are just that, the decision is up to you unless a runway is actually closed. <S> Listen out on the CTAF and listen to what the other pilots are doing, if they are using 4 then use 4 too, if they are all using 22 <S> then there is probably a reason for it. <A> Uncontrolled really means pilot controlled. <S> It is up to the pilot to determine the safest runway to accomplish his/her mission. <S> If the winds are favoring a specific runway, it would be safer to land facing into the wind. <S> If there are aircraft already in the pattern, it would be safer to keep your pattern consistent to theirs. <S> If the mission for your flight is to practice crosswind or tailwind landings (just in case you have an engine out above your particular “impossible turn” altitude), take into account your personal minimums and go for it. <S> Always communicate your intentions to your fellow pilots regardless of the runway you are using. <S> And, an overhead flyover well above Traffic Pattern Altitude beforehand is recommended. <S> Keep an eye out for anyone not communicating on their radios. <A> As PIC, you are solely responsible for the safe operation of your aircraft. <S> Unicom is an advisory service meant to assist you in that goal, but unlike ATC, you are free to ignore it. <S> I read about an incident where Unicom advised an inbound pilot that a particular runway was in use based on the last aircraft they'd heard on the radio. <S> However, the winds had since shifted and there was a NORDO plane in the pattern for the opposite runway, which the Unicom operator wasn't aware of because they didn't actually have eyes on the field. <S> I don't recall how it ended (comments welcome), but you can imagine how easily that could turn deadly.
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As the other posters have said, you can use whatever runway you want, within reason.
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What is the purpose of classifying fighters? Fighters are classified by generation, as explained in this answer . Given this Wikipedia sum up , some fighters are not clearly in a defined generation, especially for 4th generation subclasses. Thus people may not agree on a list of fighters that belongs to a generation. Some of the previous generation (generation 4, 4+, 4.5, 4++) are still actively produced (e.g. Rafale, F/A-18E/F) while the F-22 (definitely 5th generation) is no longer in production. Airframe designed a long time ago (e.g. the F-15, F/A-18) still receive updates that make it competitive on international market (the section about potential operator of the F/A-18 on Wikipedia give an overview for the F/A-18), even in front of 5th generation fighters ( at least in Canada for the F/A-18 and the F-35) Another capability we cannot rely on to define generation is stealth. The A-12 and more precisely its variant YF-12 was stealth supersonic aircraft with weapons (AIM-47) inside internal bays , but was not a 5th generation fighter.Moreover, since ECM can be fitted on a fighter , this fighter expose some stealth feature. Given those facts, it seems that since the 4th generation, knowing a fighter is classified as a specific generation does not provide information about its production year, its capabilities nor its competitivity in front of other nation's fighters. In short, since the 4th generation, generation does not provide reliable information about capabilities, features nor designed or production year. What information does the generation of a fighter give? How useful it is to know a fighter belongs to a specific generation? <Q> People like to classify things, to divide them into categories. <S> Categorizing allows people to get an initial broad understanding of a complicated subject more quickly. <S> It is therefore very useful for purposes such as marketing and articles aimed for people who aren't necessarily subject matter experts. <S> However, classification is necessarily a crude tool that often isn't exact, leading to confusion and arguments about where the category boundaries lie. <S> People who are subject matter experts, such as designers of a new fighter plane, or military analysts trying to determine the capabilities of a new secret aircraft produced by other countries, presumably don't spend much time wondering into which category to put a given aircraft. <S> Instead they focus their time on the details of the subject, the same details that are too much information for the person trying to get the quick grasp of the complicated subject. <S> To answer your questions specifically, knowing the generation of a fighter gives someone a rough idea of its capabilities, and allows the person to quickly compare a given fighter aircraft to other fighter aircraft. <A> To be clear, there is no “generation” classification for fighters. <S> This was a marketing gimmick cooked up by defense OEMs to move hardware and keep Congress from axing pet projects. <S> The generation thing appears in the 1990s in Lockheed Martin literature about the F-22, which at the time was in danger of being stillborne. <S> Nobody referred to the ATF program, which sired the F-22, as a fifth generation fighter. <S> It was a fighter program, albeit an advanced one. <S> Stealth, derived from the old Anglo Saxon word “stealeth” meaning to sneak up upon and overtake by surprise, is a generic term for a wide variety of technologies called Low Observable Technologies. <S> They are intended to reduce the signature of a person, vehicle or structure, by identifying all means by which they can be detected by sensors. <S> This includes visual, infrared, radar, thermal, acoustic, etc. <S> LOT technology then attempts minimize the footprint made. <S> Stealth appears to have been a media thing, similar to how Vespa mandarinia was dubbed ‘Murder Hornet’ - it sounds scary, which gets likes, clicks, airtime and column inches. <S> It’s origins go back to the 1980s and were most closely attached to leaks about the Have Blue and Senior Trend programs which developed the F-117 attack aircraft. <S> Stealth is also often associated with radar near invisibility and refer to aircraft whose shaping was derived from Pyotr Ufimsev’s research into accurately calculating RCS size. <S> The B-2 “Stealth” bomber program was originally know to the public as the Advanced Technology Bomber (ATB). <S> The term also got traction in Tom Clancy’s <S> book Red Storm Rising, which featured the deployment of a fictional “F-19 Ghostrider stealth fighter” on a future European battlefield against the Soviets. <S> In short fighters are fighters, stealthy or not. <A> As you can see from the Wikipedia chart, the fact that the definitions vary depending on the publication means it's all just a kind of a construct in the minds of the ones who created it. <S> In the end it's just a historical mental exercise with no particular applicability other than to be a useful shorthand when making a historical description of design over the years. <S> As far as a practical application goes, not much.
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Knowing the generation of a fighter is useful for people who aren't experts on the subject who need a quick broad understanding of the capabilities of historic and modern fighter aircraft, and who need to know roughly where a given aircraft fits into the large picture.
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Can tailwind produce reverse-thrust? I know that the answer will probably be no, and this question might sound silly, but I wanted to think outside of the box. If engine air intake comes from the front, and is pushed out through the back, what happens if the tailwind is so strong that the opposite happens, and the air is pushed in through the back of the engine? Will it create reverse-thrust? Is this dangerous? <Q> Only when on the ground, and at the inlet end, where a strong wind from the side and behind could influence the engine's ability to draw air in the front at low power settings. <S> Some engines have limitations or restrictions on how power is applied during takeoff in strong tail or quartering winds, because of initial flow disruptions at the front from air having to make a sharp corner into the intake, where large thrust increases could cause compressor stall/surge. <S> You might have a procedural requirement to advance power to some intermediate setting, then let it stabilize there before going the rest of the way to takeoff thrust. <S> The GE CF-34 has limitations like this, where winds above a certain speed and off angle a certain amount require a staged application of thrust. <S> For the engine, it's all coming from the front as soon as you are moving with any significant airspeed. <A> The ambient air will only move through the engine from back to front when the aircraft is on the ground. <S> Even then, the engine would have to be off for that to happen. <S> Otherwise, the thrust from the engine would be too great. <S> Even the electric or air starter should have enough torque to overcome the ambient air pressure before fuel ignition is achieved. <S> Go out to an airport ramp during a windy day. <S> Some turbine engines without inlet and exhaust covers will windmill. <S> In the air, a tailwind only adds to the forward velocity of the airplane as a whole. <S> The airplane is traveling through the airmass irrespective of the ground. <S> Think of it like a child’s balloon floating in a minivan on the highway. <S> The balloon does not know nor care that it’s doing 70-80 mph. <A> Whereas an airplane with a tailwind is moving at it's true airspeed (or EAS) plus the wind value, the airplane never actually experiences the tailwind, other than as expressed by its speed over the ground. <S> An airplane on the ground during engine start, with a tailwind, can experience a slightly elevated start temperature up through about 35% during the engine start. <S> Reverse thrust isn't blowing engine exhaust or air out the front of the engine. <S> it's the act of deflecting fan airflow out the sides of the engine. <S> Reverse thrust is a combination of drag rise around the engine nacelle, and a rise in intake drag and internal drag in the engine while the thrust is re-directed. <S> A tailwind can't duplicate that, and has no effect on thrust in cruise flight.
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Once you're in the air, there is no such thing as a tailwind as far as the airplane is concerned except insofar as tailwinds add to ground speed.
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Can the "G" and "VRB" wind conditions be combined in METARs? I have never seen the "VRB" (for wind direction variations < 60°; e.g. VRB12003KT) and "G" annotation (for gusts > 10KT wind speed difference; e.g. 12003GT30KT) being combined in a METAR. Until now I have just seen: VRB03KT (so "VRB" without gusts) 12003G30KT 090V150 (so "G" with wind direction variation > 60°) Why does this never happen? Is there a rule and is it not possible or does it just never happen? <Q> Yes, it is possible for a METAR to contain both VRB and G. VRB10G25KT is valid. <S> The reason it rarely happens is because, as wind speed increases, major variations in wind directions tend to disappear. <A> It appears approximately 150K times in our database of 85 million METARs [1] . <S> This database is built from data provided by NOAA and covers roughly 16 months. <S> [2] Here are several real examples from February 2019. <S> KBML 011110Z AUTO <S> VRB06G18KT 7SM OVC029 M16/ <S> M22 A3007 RMK AO2 T11611217KSZY 011115Z <S> AUTO <S> VRB06G11KT 10SM FEW050 BKN070 OVC110 08/ <S> M04 A3020 <S> RMK A01ENST <S> 011120Z <S> VRB13G28KT <S> CAVOK M02/M11 Q1011 <S> RMK WIND 300FT 11027G39KTLFBH 011130Z <S> AUTO 16009KT 9999 FEW042 OVC068 07/05 <S> Q0985 TEMPO <S> VRB15G30KT 3000 SHRA <S> BKN020CBLFRS <S> 011130Z <S> AUTO 20009KT 9999 <S> FEW016 BKN200 07/05 <S> Q0983 TEMPO <S> VRB15G25KT 2000 TSRA BKN010 <S> BKN018CB <S> 85% of METARs containing this pattern are marked as AUTO . <S> 11% of the time the pattern occurs after TEMPO , though it could also occur elsewhere in the METAR. <S> I did a quick, simple pattern match to obtain these numbers so they are approximate. <S> [1] - <S> This database is part of the VOCUS product suite. <S> I work for the company that makes VOCUS. <S> We use weather data to analyze risk prior to flight, and to provide post flight analysis. <S> [2] - I have an archive of an additional 201 million older METARs if anyone is really interested in numbers against a larger data set. <A> To elaborate on a previous answer, large changes in wind direction on short timescales tend to be caused by thermal updrafts passing through the area, tending to "suck" the wind toward their centers. <S> When the overall windspeed is high, the (relatively) small changes in wind velocity (speed and direction) caused by this phenomenon tend to be dwarfed by the overall prevailing wind. <S> In addition, strong wind tends to suppress thermal convection, at least near the ground. <S> On a windy day, there still can be some significant changes in wind speed, caused by turbulent "rotors" (tumbling masses of air) intermittently mixing the stronger wind aloft down to the surface, but these tend not to involve extreme changes in wind direction. <S> This intermittent turbulent mixing will be more pronounced on a sunny day (or with an unstable airmass) <S> than on a cloudy day (or with a stable airmass). <S> It is useful to know that even on a windy day, there can be some significant change in wind direction as the turbulent "rotors" make the wind speed increase and decrease, and it typically happens in a systematic way-- due to a phenomenon called the Eckman spiral , the wind aloft tends to be more westerly (in the northern hemisphere, and more southerly in the southern hemisphere) than the wind at the surface. <S> So as the wind gusts up to a stronger value, it typically "veers" in the direction that is aligned with the wind higher up. <S> This is good to know if you are a pilot-- and is absolutely essential to know if you are a racing sailor. <S> Similarly, as your aircraft rises up through the air after take-off, it will typically (in the northern hemisphere) tend to "feel" a temporary increase in apparent wind from the right (or a temporary decrease in apparent wind from the left), which may have some noticeable affect on handling. <S> And the reverse on landing. <S> And all the reverse in the southern hemisphere. <S> And all disappearing or being greatly reduced near the equator. <S> Since these effects are dependent on a marked change in wind direction with altitude, they tend to be more pronounced on a cloudy day or with a stable airmass, and less pronounced on a sunny day or with an unstable airmass, when the airmass tends to be more "churned up" by turbulent mixing. <A> It is possible as @tim-medora indicated in his answer. <S> Part of the reason this is possible is in the timeframe which each part of the wind information is gathered. <S> Wind direction and speed is averaged over two minutes while gusts are the maximum gust over the previous ten minutes. <S> Office of the Federal Meteorological Handbook - Surface Weather Observations and Reports Wind Direction. <S> The wind direction shall be determined by averaging the direction over a 2-minute period . <S> When the wind direction sensor(s) is out of service, at designated stations, the direction may be estimated by observing the wind cone or tee, movement of twigs, leaves, smoke, etc., or by facing into the wind in an unsheltered area. <S> Variable Wind Direction <S> The wind direction may be considered variable if, during the 2-minute evaluation period , the wind speed is 6 knots or less. <S> Also, the wind direction shall be considered variable if, during the 2-minute evaluation period, it varies by 60 degrees or more when the average wind speed is greater than 6 knots. <S> Wind Speed <S> The wind speed shall be determined by averaging the speed over a 2-minute period . <S> Atdesignated stations, Table 5-1 shall be used to estimate wind speeds when instruments are out of service or the wind speed is below the starting speed of the anemometer in use. <S> Wind Gust and Squall <S> The wind speed data for the most recent 10 minutes shall be examined to evaluate theoccurrence of gusts or squalls. <S> Gusts are indicated by rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls. <S> Squalls are indicated by a sudden onset of wind where the speed increases by at least 16 knots and is sustained at 22 knots or more for at least a minute. <S> The speed of a gust or a squall shall be the maximum instantaneous wind speed.
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As other answers say, yes, this is valid.
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