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Ejection seat assembly
SEAT CONTROL SYSTEM

Aviation Structural Mechanic E2 - How airplanes are built and how to maintain them
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rocket around the pitch axis, which changes the PRESSURE-ACTUATED 0.3-SECOND DE- thrust/cg relationship and applies a correcting LAY INITIATOR.— The 0.3-second initiator is moment. located on the rear right side of the seat above YAW THRUSTER.— To achieve safe separa- the harness release actuator. The 0.3-second tion of multicrew seat trajectories, a yaw thruster initiator is a pressure-actuated device with a conventional firing piston secured in the cocked is used on each seat to provide a controlled, lateral-angle dispersion from the aircraft’s position by a shear pin. Gas pressure from the direction of flight. Two types of yaw thrusters are rocket catapult actuates the initiator, which fires into the inlet port of the harness release actuator. used on the forward and aft seats, with location always on the inboard side of each seat. A low yaw thruster, producing approximately a 10.4 pound-second impulse for 0.1 second, is installed on each forward seat, and a high yaw thruster, producing approximately a 21.0 pound-second impulse for 0.1 second, is installed on each aft seat. The yaw thruster is ignited by high-pressure gas ported from the top of the rocket catapult. To provide proper yaw rotational impulse for each seat installation, the yaw thruster is mounted to provide a predetermined moment arm about the center of gravity of the seat/crew member system. The mounting bracket for each thruster incorporates a boss that, when combined with a fixed stop permanently mounted on each guide rail, will prevent incorrect installation. The right and left seats are yawed to produce changes in the trajectory paths. Each of the four crew member seats will be separated from the others at parachute full-open condition under nominal lateral center-of-gravity conditions. YAW VANE.— To assist in providing the proper yaw rotation at higher airspeeds, an aerodynamic yaw vane is installed on the out- HARNESS RELEASE ACTUATOR.— The actuator is mounted on the rear right side of the seat. The actuator contains a piston and rod that are actuated by a 0.3-second delay initiator firing into the inlet port. Gas pressure exits from the outlet port to actuate the man/seat separator rocket. The piston rod, which extends below the actuator, is connected to the harness release bell crank. The bell crank initiates simultaneous automatic actuation of each component of the harness release system to cause man/seat separa- tion during seat ejection. If the lap belts and shoulder harness assemblies fail to release automatically, the crew member can actuate the harness release handle to release the assemblies. The handle is also useful for routine removal and installation of the parachute and survival kit. The following components are connected to the multiple arm bell crank: harness release actuator piston rod, survival kit retaining pins, inertia reel straps retaining pin cable, harness release handle cable, and bell crank return spring. The actuator also actuates the firing control disconnect actuating arm. board, lower aft side of each seat. The yaw vane MAN/SEAT SEPARATOR ROCKET.— The deploys just as the seat leaves the guide rails and separator rocket is mounted on the aft inboard presents a drag area of 1/2 square foot to yaw side of the headrest area of each seat. The the seat approximately 20 degrees. At this separator rocket is used to separate the crew position, the vane is blanked by the man/seat member from the seat and drive the seat into a structure, and becomes ineffective in creating any divergent trajectory. Pressure from the harness further increase in the degree of rotation. release actuator outlet port is used to initiate the Harness Release and Seat Separation The harness release system provides automatic release of the shoulder harness and lap belts during the ejection sequence. The survival kit and shoulder harness are locked in the seat by three retaining pins, two through the survival kit lugs and one through the shoulder harness inertia reel strap lugs. Automatic release from the seat during the ejection sequence is accomplished by the harness release actuator, using a pressure- actuated 0.3-second delay initiator. Gas pressure, which exits from the outlet port of the harness release actuator, is used to actuate the man/seat separator rocket in the seat separation subsystem. 6-6 separator rocket. The separator rocket nozzle is oriented to direct the exhaust plume forward, up, and away from the crew member. Aircraft-Attached Ejection Seat Components The following ejection seat related com- ponents are located on the aircraft structure and remain in the aircraft when the seat is removed for maintenance. GUIDE RAILS.— Two guide rails are located on each canted bulkhead behind each crew member. Each set of guide rails is machined from aluminum extrusions. Each outboard rail has a







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