drogue gun firing mechanism. This releases the spring-loaded firing pin. Firing pin movement is slowed for 0.5 second by an escapement mechanism to allow the ejection seat to clear the aircraft. After a 0.5-second delay, the firing pin activates the primary cartridge. Heat and pressure from the primary cartridge cause the secondary cartridge to fire. The gas produced by both car- tridges shears the shear pin and expels the piston from the drogue gun barrel. The drogue withdrawal line is attached to the piston. When expelled, the piston withdraws the pin from the closure flaps of the parachute container and deploys the drogue parachutes. The secondary cartridge serves as a backup system to the mechanically fired primary system. The cartridges in the time-release mechanism and manual override initiator provide gas pressure to the gas-operated secondary firing mechanism of the drogue gun. If the drogue gun primary firing mechanism fails, the gas-operated secondary firing mechanism cartridge will be fired by the secondary cartridge and the combined gas pressure will expel the piston from the drogue gun barrel to deploy the drogue parachutes. TIME-RELEASE MECHANISM.— As the ejection seat rises, the trip rod also withdraws the firing link from the TRM and releases a spring- loaded firing pin. Firing pin movement is prevented for 1.5 seconds by a barostat and g-controller. When the altitude of the seat is less than 14,500 feet and acceleration forces are less than 3 g’s, the barostat and g-controller release the firing mechanism. After the 1.5-second delay, the firing pin activates the cartridge. The gas produced by the cartridge passes to the upper body chamber and forces the shackle plunger down. This allows the scissor mechanism to open. At the same time, the gas actuates the connecting rod in the lower body and opens the inertia reel locks. Gas pressure is also provided to operate the piston to release the personnel parachute, manual override initiator, and the drogue gun secondary cartridge. SCISSOR MECHANISM.— When the TRM cartridge fires, the shackle plunger retracts into the upper body of the TRM. This action allows the movable jaw of the scissor mechanism to open and release the personnel parachute from the container. INERTIA REEL ASSEMBLY.— During the ejection sequence, gas pressure is used to fire the inertia reel cartridge. The gas pressure forces the head of the piston along the cylinder. The horizontal movement of the piston is transmitted by a threaded drive screw to rotate the ratchet wheel. The rotation of the ratchet wheel retracts the inertia reel straps and restrains the pilot in the seat. Then the locking pawl locks the spools in the retracted position. Extension of the inertia reel straps at excessive speed causes the governor pawls to rotate outward because of centrifugal force. They engage the rack on the housing, which prevents any additional extension of the straps. When the shoulder harness control handle is in the rear position, the system restrains the pilot from moving forward. With no tension applied to the inertia reel straps, the pawl will reset itself and disengage from the rack. This will allow free extension of the straps. ROCKET MOTOR INITIATOR.— During the ejection sequence, the static line connected to the drogue gun trip rod and to the rocket motor initiator is withdrawn from the aft initiator housing. When the static line is extended to approximately 72 inches, a spring-loaded plunger is unlocked. The plunger rotates the quadrant lever and removes the sear from the firing mechanism. Removal of the sear fires the cartridge in the breech. The gas produced is routed to the rocket motor firing mechanism, which ignites the rocket motor. AIRCRAFT SEAT PARACHUTE.— The drogue shackle, which contains the parachute withdrawal line and extender strap, allows the drogues to be deployed without extraction of the personnel parachute. A mechanical lock secures the parachute withdrawal line to prevent premature deployment until pilot and seat separation has occurred. The lock is released by a piston in the upper body of the time-release, mechanism. The parachute risers are routed down the forward side of the parachute container. Quick- release fittings are located on the end of the risers and connect to the pilot’s torso harness. The inertia reel straps are routed from the inertia reel, through the parachute riser roller fittings, and are secured in the inertia reel locks. SEAT BUCKET SUPPORTED COMPONENTS The seat bucket supports several components on the lower portion of the ejection seat. The operation of these components is discussed in the following paragraphs. 6-37