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delay “Gas Generator.” The Quickmatch ignites the delay, which in turn fires a Secondary |
Expulsion charge. This charge functions as the first, producing pressure that shears another set of |
12 pins, evenly spaced around the circumference of the flare. Once again the pressure provides an |
acceleration/deceleration force to the Drogue Housing and the Candle & Parachute Assembly. |
Attached to the Pusher Plate is the cord for the Pilot Chute. As the Pilot Chute deploys, it pulls |
the Main Chute assembly out of its housing (Parachute Insert) for Main Chute deployment. |
Attached to the Main Chute support cable is a Lanyard that runs through an internal raceway in |
the Candle and is attached to the Slider assembly in the Igniter assembly. As the main chute is |
deployed, it pulls the Lanyard with a minimum force of 40 pounds. This force shears a shear pin |
and moves the slider assembly into the firing position, cocks and releases the firing hammer and |
fires the ignition primer. During launch of the Rocket, acceleration forces of at least 17 G for |
duration of approximately one second withdrew the weight assembly of the “Zig-Zag” ignition |
safe/arm mechanism from its saving position in the slider assembly, allowing Slider movement. |
The output of the ignition primer is directed into a cavity containing boron pellets. The fire from |
the boron pellets is directed on the forward face of the flare’s illuminant Candle and also on a |
small propellant wafer which acts as an ignition booster. The Candle produces light in the near IR |
spectrum for about 180 seconds. The main parachute allows for a descent rate of approximately |
13 feet per second. |
Tabulated data: |
M257 Illumination Flare w/ M442 Fuze |
Operating temperature limits: -25 oF to +140 oF |
(-31.35 oC to +59.40 oC) |
Candle composition: Magnesium Sodium Nitrate |
Candle weight: 5.44 lb (2.47 kg) |
Illumination intensity, visible: 817.19 CP (avg.) |
infrared: 250.02 watts/sr (avg.) |
Illumination duration: 197.38 sec (avg.) |
Function time: 14.23 sec (avg.) |
Shipping and storage data: |
Storage class/SCG: 1.2 G |
DOT shipping class: A |
DOT designation: Rocket Ammunition with Illuminating Projectile |
Field Storage: Group D |
NSN: 1340-01-268-7175 |
DODIC: H183 |
UNO Serial No. |
M278 IR Flare w/ M442 Fuze |
DODIC: H154 |
UNO Serial No. |
the 7-tube launcher continues to use a laminated stack. |
experiences from the fire control is 0.06 seconds. |
minimize the heat signature of the launcher after rocket firings. |
RMS Display Unit RMS Operations Unit |
The M138 Rocket Management Subsystem (RMS) is a pilot-operated subsystem that |
interfaces with the wing stores subsystem in the helicopter. The RMS operates from power |
supplied by the aircraft and consists of one Display Unit and four Operations Units. The RMS |
enables the aircraft pilot to select and launch MK 40 or MK 66 rocket motors with the desired |
warhead/fuze combination from two or four 7- or 19-tube launchers mounted under the aircraft |
stub wings. The RMS automatically senses the quantity and type of launcher installed and |
automatically sets its firing sequence to agree with the tube numbering of the launcher on board. |
Should one or more launchers be disabled, the RMS will cause the corresponding launcher on the |
opposite side of the fuselage to become inactive to maintain in-flight stability by equalizing the |
load of unfired rockets. |
Rockets are loaded according to type (warhead/fuze) in up to five loading zones, and the types |
loaded in each zone are indicated by manually setting five 12-position thumb wheel switches on |
the Display Unit panel. The switch positions are marked with two- or three-letter descriptors that |
represent the available warhead/fuze configurations. When power is applied to the RMS, it |
automatically inventories the rounds loaded in each zone and provides the pilot with a numeric |
display of the quantities available for launching from each zone. By setting switches on the face |
of the Display Unit, the pilot can select the rocket types to be launched, set the fuzes according to |
the tactical situation, and determine the quantities of rockets to be launched in each volley. |
Rockets are then launched when the pilot or copilot/gunner squeezes the trigger switch on the |
cyclic stick. Should the trigger switch be released before the entire volley has been launched, the |
numeric display on the face of the Display Unit is immediately updated to continuously reflect the |
quantities of rockets remaining in each loading zone. Refer to TM 9-1090-207-13&P for |
additional information pertaining to RMS components. |
The primary objectives of the remotely settable fuze concept were to use very inexpensive |
components in the fuze itself, eliminate any battery required to run the electronics during the fuze |
run time, and accomplish the accuracy goals throughout the total environmental range. The |
solution was to select a resistance-capacitance technique wherein relatively inexpensive, broad- |
tolerance (+/- 20 percent) components could be used for high-volume production of relatively |
inexpensive electronic fuzes. To accurately set the capacitance-charged fuzes for the desired run |
time throughout the environmental range requires a compensating setter located in the aircraft. |
The setter, immediately prior to launching a rocket, determines the amount of energy required by |
the fuze timing capacitor for the component variations existing along with temperature effects to |
run the fuze timing circuitry for the range selected. The setter then charges the timing capacitor |
and the storage capacitor used as both the power source to run the electronics and the power |
source to initiate the pyrotechnic train through initiation of the electric detonator in the fuze |
safeing and arming device. The setter must be capable of compensating for 20 percent variations |
in component value and for variations in fuze run time due to temperature effects on individual |
fuzes. Since each fuze is unique, each fuze must receive a different amount of energy in its timing |
sequence, whether it be singles, pairs, or quads, fuzes must therefore receive different amounts of |
energy to accomplish the same set time. Therefore, just prior to firing, the individual fuze and its |
setter compose an integral subsystem which must perform its function accurately across the entire |
environmental spectrum, compensating for inherent errors in individual fuzes. |
The Display Unit is a cockpit-mounted line-replaceable unit that presents the pilot with |
controls and displays for inventorying and controlling the launching of aerial rockets. It also |
contains the power supply and other common circuits necessary for the RMS components to |
operate as a subsystem. The Display Unit transmits the electrical command signals selected by the |
pilot to the Operations Units. One Operations Unit is used for each launcher and contains the |
circuitry that sets the fuzes and the circuitry that provides the rocket motor squib firing pulses for |
the rockets loaded into the associated launcher. |
Additional description of the RMS is contained in enclosure 1. This is an early system |
description as taken from material used for training (extraneous pages have been extracted) of |
what eventually became the M138 RMS. It was originally fitted into the AH-1S model of the |
Cobra helicopter. The weight of the display unit is 6 pounds and of the operations unit is 2 |
pounds each. The NSN for the M138 RMS is 1090-01-077-8939. A variation of this system |
known as the Armament Management System was fitted into the AH-1G model of the Cobra |
helicopter. It uses two zones and was intended as an interim solution for an eventual upgrade to |
the M138 RMS. |
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