BAROSTATIC RELEASE UNIT (BRU).-

When the RH multipurpose initiator cartridge fires during ejection, gas pressure from the cartridge enters the piston housing and moves the piston upwards, rupturing the frangible disc and allowing the pawl to pivot clear of the rack assembly slotted end. When the altitude is such that the barostat is not restraining the mechanism, the rack assembly will rise under the action of its spring, the rate of ascent being governed by the delay mechanism. After the delay has elapsed, the rack disengages from the gear train and the firing pin rises rapidly to strike the cartridge. If the cartridge has not previously been fired electrically by the sequencer, the gas produced by the cartridge passes out of the BRU to operate the upperand lower-harness locks and the secondary cartridge in the parachute deployment rocket motor.

DROGUE DEPLOYMENT CATAPULT.-

During ejection, the drogue deployment catapult fires and ejects the drogue and canister. As the drogue deploys, the bridle breaks out of the frangible container and detaches from the channels on the main beams. The drogue stabilizes and decelerates the seat. In the high-altitude mode, the seat descends rapidly on the drogue to a predetermined altitude. The drogue bridle releases then operate, the personnel parachute deploys, and the occupant separates from the seat. In all other modes, the upper and lower drogue bridle releases operate after a short predetermined delay, as the personnel parachute deploys and seat/man separation occurs.

The impulse cartridge is fired by an electrical signal from the sequencer. Gas from the cartridge propels the telescopic piston upwards, shearing the end cap rivets. Continued movement of the piston thrusts the canister upwards, shearing the rivets in the threaded ring and propelling the canister and drogue assembly away from the seat. The bridle is pulled from its frangible container and out of the channels on the seat's main beams. As the bridle reaches full extension, inertia causes the canister to fly clear, and the drogue is extracted and deployed to stabilize and decelerate the seat.

MULTIPURPOSE INITIATOR.- When ejection is initiated, the catapult ballistic latches operate to retain both multipurpose initiator lanyard spigots. As the seat moves up the guide rails, the static lanyard spigots break the shear pins and the lanyards pay out from the housings. When the lanyards become taut, the upper fittings withdraw the firing pins against spring pressure until the wedge-shaped disconnect devices separate. The firing pins move rapidly upward under spring pressure to fire the cartridges. The gas generated passes to the underside of the piston heads on the start switch plungers. The plungers move up, shearing the shear pins, until the goldplated portions of the plungers complete an electrical connection in the switch assemblies. Sequencer timing then commences.

Gas from the cartridges also passes out of the units to the barostatic release unit (RH side only), the pitot deployment mechanisms, and the underseat rocket motor.

PITOT ASSEMBLY.- When the pitot assembly is installed on the seat beam, the inboard static pressure connector connects to a void in the seat beam. The sequencer is installed on the forward face of both pitot assemblies and connects to the dynamic and forward static pressure connectors.

On ejection, gas pressure from the impulse cartridges in the multipurpose initiators enters the body and operates the lower piston. Movement of the lower piston pushes the pitot arm locking plunger out of engagement with the hole in the body, and at the same time, opens a gas passage to the upper piston. The upper piston moves outward to move the pitot arm to the deployed position. The pitot arm locking plunger engages with the second hole in the body and locks the pitot arm in the deployed position.

RH AND LH BALLISTIC MANIFOLDS.-

Pulling the ejection control handle withdraws the handle from its housing and both sears from the seat initiator firing mechanisms to fire both impulse cartridges (fig. 5-31).

Gas pressure from the RH initiator cartridge withdraws the pin puller, freeing the emergency harness restraint release linkage (figs. 5-32 and 5-33). RH gas pressure also passes to the following:

1. The shoulder harness reel to initiate harness retraction.

2. The thermal batteries.

3. The 0.75-second (forward seat) delay cartridge-actuated initiator mounted on the LH ballistic manifold.

4. The 0.30-second (aft seat) delay cartridge-

Figure ^{5-31.-Seat initiator.} actuated initiator mounted on the RH ballistic manifold.

Figure 5-32.-Forward ejection seat gas flow diagram. 5-31

Figure 5-33.-Aft ejection seat gas flow diagram.

Gas pressure from the LH impulse cartridge passes to the following:

1. The thermal batteries.

2. The 0.75-second (forward seat) or 0.30second (aft seat) delay cartridge-actuated initiator mounted on the LH ballistic manifold, which passes gas to the LH inlet of the catapult manifold valve to initiate the catapult.

THERMAL BATTERIES.- To provide system redundancy, each battery is initiated independently by a manifold-mounted, gasoperated firing mechanism. Both firing mechanisms are initiated by gas pressure from the seat initiator cartridges.