The Ejection Site
B-52 Egress System


1. Hatches and Components
226.Escape hatches
227.Component description
2. Ejection Systems
228.Upward system
229.Downward ejection system

The B-52G aircraft is a heavy bomber equipped with six crew stations. Each crew station has its escape hatch and ejection seat. This unit contains a description of the various components that make up the B-52G egress systems. These systems include the upward ejection system, downward ejection system, and their respective escape hatches.

Figure 1. B-52 Egress System Crew Stations.

1. Hatches and Components

In this section, we will discuss the escape hatches and some of the components that make up the emergency escape system on the B-52 aircraft. We will begin with a discussion of the pilot and copilot hatches then move on to electronic warfare officer, gunner, navigator, and the radar navigator hatches. We will conclude this section with a look at a few of the components that make up the egress system.

226. Escape hatches

Each crew station has an independent ejection system that must be initiated by the crewmember. The ejection systems include an escape hatch for each ejection seat. In figure 1, you see the seat and hatch arrangement. The upper hatches have both inside and outside manual handles, while the downward hatches have only inside handles. The handles unlock, open and close the hatch. The hatch is jettisoned during the seat ejection sequence. Let's begin with a look at the pilot and copilot hatches.

Figure 2. Pilot and Copilot Escape Hatches.

Pilot and copilot escape hatches. The pilot and copilot escape hatches are situated directly above their ejection seats and the mechanism for each is identical (fig. 2). The hatches serve a dual purpose because they provide an opening for emergency seat ejection as well as a means of ground entry or exit to or from the forward crew compartment after ditching or crash landing. Opening of the hatches may be accomplished by three methods: an outside handle, an inside handle, and a thruster mechanism for jettisoning during ejection. If a hatch is opened using the inside handle, it must be closed using the same handle. This is because the handles completely disengage from the torque tubes as the hatch moves to the fully CLOSED and LOCKED position.

The hatches are hinged at the aft end with hinges that disengage when the hatches are swung open. Two jack arms at the front end and six latch hooks (three on each side) close and lock the hatch. These jack arms and latch hooks are connected to two torque tubes that run the length of the hatch. The torque tubes rotate in reverse of each other to close and lock the hatch. When the torque tubes are rotated, the jack arms, which are guided by tracks on the forward hatch well opening, draw the hatch closed and at the same time actuate the latches that extend outward to engage the latch arms. The inside and outside handles and the hatch jettison thruster are connected to the torque tubes.

Figure 3. EWO and Gunner Escape Hatches.

Electronic warfare officer (EWO) and gunner escape hatches. The EWO and gunner escape hatches (fig. 3) are similar to the pilot and copilot hatches in design and operation except that a lifter mechanism has been incorporated in the jettison mechanism. This mechanism assists in jettisoning the hatch when the hatch jettison thruster is fired. The lifter mechanism consists of a lifter, jettison assist straps, and a pushoff mechanism. The lifter is a door that rests on the outside of the hatch and is hinged at the aft end. It is held against the hatch by pushrods on the forward end. When the hatch is in the normal position, the pushrod arms engage a ball on the ends of the pushrods. The lifter mechanism is held in the normal position by the thruster. When the thruster is fired, the lifter torque shaft rotates causing the pushrod arms to rotate, pushing the pushrods outboard. At the fully rotated position, the pushrods disengage from the pushrod arms, allowing the lifter to swing free in the airstream. Jettison assist straps attached to the hatch and to the lifter stop the lifter after it has swung away from the hatch 30. These straps absorb the shock of extending the lifter and transfer the air load from the lifter to the hatch to assist in jettisoning the hatch.

Figure 4. Navigator and Radar Navigator Escape Hatches.

Navigator and radar navigator escape hatches. In figure 1, you see that the navigator and radar navigator escape hatches are located directly below the downward ejection seats. The hatches (fig. 4) are closed normally; their main purpose is to provide an opening for the downward ejection seats during an emergency. An emergency escape hatch jettison handle, which is located in the forward inboard corner of the escape hatch well, provides an alternate means of jettisoning the escape hatch for bailout if the normal system fails to operate. When jettisoning takes place, gas pressure from the arming initiator fires the hatch jettison thruster. Gas expansion in the thruster causes the thruster shaft to extend. The thruster shaft is connected to the torque tube by a thruster extension and the actuator arm (fig. 5). One side of the thruster extension contacts a lug on the lock cam. The thruster extension is slotted so that as the thruster shaft. extends, the thruster extension first rotates the lock cam. When the lock cam has rotated far enough to unlock the mechanism, the thruster extension picks up the pin through the actuator arm causing it to rotate. A lug on the actuator arm bears against the lock arm causing the torque tubes to rotate and open the forward end of the hatch into the slipstream where the hatch is carried free of the aircraft. A hydraulic damper is incorporated in the mechanism in such a manner that the shock produced by the thruster is reduced. Also, a lifter mechanism assists in jettisoning the hatch when the hatch jettison thruster is fired. The jettison assist straps stop the lifter after it has swung approximately 25 away from the hatch.

Figure 5. Thruster Extention and Actuator Arm.

Escape hatch warning system. The hatch warning system is a 24-volt DC electrical warning system that receives power from the pilot auxiliary circuit breaker panel. All six escape hatches are included in the system. The forward entry door and rear access door are connected also to this circuit. The power circuit is so arranged that an amber warning light on the pilot instrument panel comes on when one or more of the hatches are open.

Each escape hatch is equipped with a microswitch that is part of the hatch warning circuit. These switches are spring-loaded to the closed position and close the circuit to the pilot instrument panel warning light that comes on when any hatch is not closed and locked. The switch is actuated by the lockpin in the escape hatch locking mechanism. The hatch position warning circuit informs the pilot and copilot of a hatch that is not closed and locked.

227. Component description

Now let's take a look at some of the components that make up the escape system. This listing is not intended to be all inclusive. It only covers those areas that are unique to the B-52.

Thrusters. A thruster is a device that derives its energy from an explosive cartridge contained within the unit. When ballistic gas pressure is applied to the inlet port, the firing pin shear pin is sheared and the firing pin is propelled against the cartridge. As the cartridge fires, the burning propellant produces ballistic gas pressure that moves an integral piston and imparts a thrust to an attached load.

Control column stowage thruster. The control column stowage thruster is a cartridge-actuated device that releases the stowage spring to move the control column forward so that it will not interfere with the seat ejections Two of these thrusters are used in the aircraft one for the pilot ejection system and one for the copilot system. The pilot control column stowage thruster is located in the control column disconnect mechanism below the pilot side panel. The copilot control column stowage thruster is located under the copilot side panel.

Fire control support stowage thruster. The gunner's fire control support stowage thruster is a cartridge-actuated device that stows the gunner fire control support during the seat ejection sequence. The thruster is located aft of the gunner's instrumenent panel.

Figure 6. Table Storage Thrusters.

When the thruster is fired, the latching mechanism that holds the fire control support in the extended position is released, allowing the thruster to pull the support to the stowed position.

Table stowage thrusters. The radar navigator and navigator use table stowage thrusters (fig. 6) to stow their work tables automatically during the seat ejection sequence. The thrusters are located below the instrument panel and between the two tables. Each thruster is gas fired by a table stowage thruster initiator which is fired by gas expansion from the arming initiator. Slip joints on the aft end of the thrusters allow the tables to be stowed manually by pushing them forward.

Leg guard thruster. The downward ejection seats leg guards are rotated by a thruster attached to the bottom of the seat bucket and to a linkage attached to the leg guard torque robe. The thruster is fired by gas expansion from the arming initiator. The force of the thruster acts on the leg guard torque tube, rotating the leg guards to the ejection position.

Catapults. The ejection seat catapult is a three-tube telescoping ejection mechanism powered by an explosive charge. The catapult is made up of an outer tube, an intermediate tube, and an inner tube that contains the explosive charge. The inner tube has a trunnion which attaches to the ejectable rails and the outer tube has a trunion which attaches to the fixed seat rails. The intermediate tube serves to increase the effective stroke of the catapult and thus cushion the acceleration force. The catapult is fired by an initiator in the ejection system after the proper sequence of events has taken place. Upon ignition of the explosive charge, the catapult extends and ejects the attached seat.

Man-seat separation system. The EWO, gunner, navigator, and radar navigator ejection seats are provided with a man-seat separation system that provides positive separation of crewmembers after ejection from the aircraft. The system consists of a reel-type ballistic actuator, jackshaft, and a harness made of two nylon straps. The harness is installed in the seat under the global survival kit and parachute. The lower end of the harness is attached to the forward side of the seat bucket and the upper end is attached to the jackshaft on the back side of the seat. The jackshaft is driven by the ballistic actuator which is connected by ballistic tubing to the man-seat separation booster initiator. The booster initiator is connected to both integrated harness release initiators. When either integrated harness release initiator is fired releasing the integrated harness, gas pressure from the initiator also fires the man-seat separation booster initiator that in turn fires the cartridge in the actuator. After the integrated harness is released, the actuator rotates the jackshaft pulling the harness tight forming one side of a triangle, the other two sides form the seat bottom and seat back. As the man-seat separation harness is pulled tight, the harness throws the occupant clear of the seat.

Man-seat separation (rotary) actuator. Rotary actuators are ballistic gas pressure-actuated devices designed to forcibly separate the crewmember from the seat after ejection. When gas pressure is applied to the inlet port of the actuator, the firing pin is propelled against the cartridge. As the cartridge fires, the resulting gas pressure exerts force on the bottom of the ballscrew. Linear motion of the ballscrew causes the ballnut to rotate and wind in the webbing. As the webbing becomes taut, the crewmember is forced from the seat.

Integrated harness attachment fittings. Each of the upward ejection seats has three integrated harness attachment fittings. Two of the attachment fittings, one on each side of the seat bucket, hold the lap belts in place, and the third, just below the headrest, attaches the upper restraint to the inertia reel. The integrated harness release handle, which is located on the left side of the seat bucket, is used to manually unlock the attachment fittings. The integrated harness release pin-pull cylinder is operated by gas pressure and is located on the back of the seat bucket. This cylinder automatically releases the attachment fittings during seat ejection. The integrated harness pin-pull cylinder receives the gas pressure from two sources:

(1) The integrated harness release 0.30-second delay initiator that is initiated when the catapult is fired.

(2) The integrated harness zero delay initiator that is mechanically tripped as the ejection seat leaves the intermediate rails.

The 0.30-delay initiator is an automatic backup in the event the zero delay fails to fire.

Each attachment fitting consists of a slotted fitting and a bellcrank-type hook. When the end fitting of the harness is inserted in the slot, the hook rotates into a hole in the harness end fitting. A locking device then locks the hook in this position, attaching the harness to the attachment fitting. Pulling up on the harness release handle unlocks the attachment hooks and allows the harness fittings to pull free. Also, the left attachment fitting is equipped with a receptacle for attaching the personnel parachute lanyard, called the gold key, to the seat. Attaching the parachute lanyard or gold key to the seat results in automatic parachute deployment upon person-seat separation.

Ankle restraints. The downward ejection seats are equipped with ankle restraints that hold the occupant's ankles in place during the ejection sequence. The restraints are located on the lower forward part of the seat in such a position that the ankle restraint triggers behind each ankle cause the restraints to rotate around the ankles when touched by the legs. This action must be accomplished before pulling the ejection control handle. In their final deployed position, the restraints can rotate out but not upward. If for any reason it is decided not to complete the ejection sequence, the ankle restraints may be restored to the stowed position by rotating the ankle restraints out and down from the seat. The ankle restraints rotate to their deployed position any time the ankle restraint triggers are depressed.

Drogue parachute. The upward ejection seats are equipped with a drogue parachute that deploys immediately after the seat departs the aircraft. The deployed parachute stabilizes and decelerates the ejection seat to assist in the positive separation of the seat occupant.

On pilot and copilot seats, the drogue parachute pack is supported above the headrest by tubular arms that are attached to the ejectable rails. The parachute support is held in position by a latch assembly that is actuated by a pin-pull cylinder. During the seat ejection sequence, the ballistically actuated pin-pull cylinder releases the spring-loaded parachute support that extends and rotates away from the seat as the seat moves up the rails and departs the aircraft. The parachute support arms rotate aft and lock in trail position at the limit of the restraining straps. The drogue parachute ripcord is pulled to deploy the parachute as the support rotates to the trail position.

On EWO and gunner seats, the drogue parachute pack is stowed between the drag panel and underside of the seat bucket. The pack is attached to the seat bucket by a latch mechanism. As the arming levers are rotated up, the drag panel is released and allowed to drop down. During initial ejection from the aircraft, gravity and catapult induced acceleration cause the drag panel to rotate downward to the limit of the restraint cables. The sliding plate extends from the drag panel and pulls the parachute bridle lines from their stowage pouches. As the seat and ejectable rails are unlatched from the intermediate rails and continue their upward travel, the static line, which is attached to the intermediate rails, releases the latch securing the drogue parachute to the bottom of the seat bucket. The drogue parachute is pulled away from the seat by the static line until the bridle lines become taut. At this point, the static line pulls the parachute pack away from the parachute and deployment of the parachute is accomplished.

Chapter 2. Ejection Systems

In this section we will take a look at the ejection systems. We will start with a description of the upward system. Then we will move on to the upward ejection seats. Next we will discuss the sequence of events during an ejection. Once we have finished with the upward system, we will move on to the downward system.

228. Upward system

The upward ejection system provides emergency escape provisions for the pilot, copilot, electronic warfare officer (EWO), and gunner by upward ejection of their seats. Each seat has its own ejection system consisting of the seat and the escape hatch, which is located directly overhead. There are no connections between the ejection systems, therefore, each crewmember must initiate ejection individually. Operation, once initiated, is fully automatic. Operation of the seats is similar except that the EWO and gunner seats face aft and contain no control column stowage facilities. The gunner fire control support is stowed automatically and in the same manner as the pilot and copilot control columns. Ejection of the seats and escape hatches is initiated by a series of ballistic devices and linkages incorporated in the seat. Each seat is the catapult type equipped with arming levers and triggers.

Figure 7. Upward Ejection Seat.

Upward ejection seat description. In figure 7, you see that the upward ejection seats are bucket-type seats located under the upward ejection escape hatches. A seat consists of the seat bucket (item 1 ), three seat positioning actuators (item 2), the ejectable rails (item 3), the fixed rails (item 4), and telescoping intermediate rails (item 5). The seat bucket is equipped with an inertia reel, a survival kit (item 6), adjustable armrests (item 7), headrest (item 8), catapult trigger (item 9), unlocking lever (item 10), arming lever (item 11 ), leg support (or drag panel on EWO and gunner seats) (item 12), provisions for use of an integrated harness, and a drogue parachute (item 13). The pilot and copilot seats are provided also with a drogue parachute support (item 14) that aids in deployment of the parachute. The seat is provided with a personnel parachute (item 15) and a manual opening safety belt (item 16). The armrests on each side of the seat are adjustable up and down to allow freedom of movement of the occupant and easy access to the seat. The ejection controls are located on the forward end of the armrests. They consist of the unlocking lever, a loop-type arming lever, and the catapult firing trigger. The controls have a dual capability; that is, either right or left hand controls will arm the seat and fire the catapult. Three attaching fittings (item 17) are provided for use of the integrated harness, one located on each side of the seat bucket and one just below the headrest. The leg support (or drag panel), is hinged on the lower forward edge of the seat bucket in such a manner that it can be folded back when not in use and is automatically extended when the seat is armed. The seat bucket is attached to the ejectable rails by three seat positioning actuators which allow the seat bucket to be adjusted up and down, fore and aft, and tilted. The telescoping intermediate rails and the fixed rails guide the ejectable rails and seat upward when ejected from the aircraft. All tube runs in the upward ejection system are made up of sections of plastic metal-armored flexible tube.

Operation. Ejection of the seats and escape hatches is initiated by a series of ballistic devices and linkages incorporated in the seat. Each seat is the catapult type equipped with arming levers and triggers.

When the arming levers are rotated to the up position, the pilot or copilot control column or gunner fire control support is stowed, the shoulder harness is locked, the hatch is jettisoned, and the ejection seat is armed. On pilot and copilot seats, the leg support is released also and the drogue parachute support is unlatched and extends upward. On EWO and gunner seats, the drag panel located under the seat releases and drops down. The occupant must still pull the trigger located on either the right or left armrest before the catapult is fired and ejection occurs. As the catapult is fired, a time-delay initiator is ballistically fired, also. This delay initiator, together with a zero delay initiator that is mechanically tripped as the ejection seat leaves the intermediate rails, releases the occupant from the seat after it has cleared the aircraft. Also, as the pilot or copilot ejection seat leaves the aircraft, the drogue parachute support rotates away from the seat and the drogue parachute is deployed. As the EWO or gunner seat accelerates up the rails, the drag panel rotates downward and the drogue parachute is deployed as the seat leaves the aircraft. A man-seat separation system is provided also on the EWO and gunner seats to give positive separation of the seat occupant after ejection from the aircraft.

The hatches are equipped with inside and outside handles for manual operation. Each hatch is provided with a warning switch that causes an amber light on the pilot instrument panel to come on when the hatch is not closed and locked properly.

Figure 8. Pilot and Copilot Ejection Sequence.

Pilot and copilot ejection sequence. The upward ejection systems are basically the same. The hatches are jettisoned when the arming levers are rotated, and the seats eject when the triggers are squeezed. Refer to figure 8 as we discuss the ejection sequence.

To begin the ejection sequence, raise both armrests to the up position and rotate either or both arming levers. The arming levers are interconnected, therefore, rotating one will rotate the other.

Rotating the arming levers fires an M3 arming initiator, locks the inertia reel, releases the leg support, and exposes the left or right trigger. Gas pressure from the M3A2 arming initiator fires the M5A2 hatch jettison booster initiator and control column stowage thruster which stows the control column. Gas pressure from the M5A2 booster initiator fires the M1A2 hatch jettison thruster, which, in turn, jettisons the hatch. As the hatch is jettisoned, the M3A2 catapult safety pin-pull initiator is fired by means of a telescoping linkage.

Gas expansion from the catapult safety pin-pull initiator operates the catapult safety pin-pull cylinder and fires the drogue parachute support arm release initiator. Operation of the catapult safety pin-pull cylinder retracts the safety pin from the M3A2 catapult initiator, thus arming seat. If the catapult safety pin-pull initiator fails to fire when the hatch is jettisoned, pulling the manual safety pin-pull lever operates the safety pin-pull cylinder manually. Gas expansion from the drogue parachute support arm release initiator operates the drogue parachute support arm release pin-pull cylinder retracting latch mechanism that allows the support arms to extend and rotate away from the seat. The parachute support will not rotate away from the seat until the seat is ejected.

The next action that the crewmember must take is to squeeze the left or right trigger. The motion of the trigger linkage fires the catapult initiator sending gas presswe to fire the M3A1 catapult and the 0.30-second delay M26 integrated harness release delay initiator. Firing of the catapult causes the seat, ejectable rails, and intermediate rails to move up the fixed rails.

The drogue parachute support moves away from the seat as the seat moves upward through the hatch opening. As the parachute support moves away from the seat, the drogue parachute lanyard is pulled from the drogue parachute pack thus allowing the pack to be mined inside out by spring force resulting in parachute deployment. The drogue parachute support rotates away from the seat until the restraint straps become taut.

As the latch mechanisms in the ejectable rails move past the top of the fixed rails, the latches are tripped thus disengaging the ejectable rails from the intermediate rails. The intermediate rails contact the snubbers mounted on the fixed rails which prevent the intermediate rails from moving upward with the seat and ejectable rails.

As the seat and ejectable rails continue to move upward on the intermediate rails, the integrated harness release zero delay initiator is fired by means of a trip attached to the intermediate rails.

Gas expansion from the M26 integrated harness release delay and the M27 zero delay initiators cause the integrated harness release pin-pull cylinder to operate, thus allowing the occupant to leave the seat.

Figure 9. EWO and Gunner Ejection Sequence.

EWO and gunner ejection sequence. To begin the ejection sequence on the EWO and gunner seats, lift both armrests to the up position and rotate either or both arming levers. These arming levers are interconnected, therefore, rotating one will rotate the other. Refer to figure 9 as we discuss the EWO and Gunner ejection sequence.

(1) Rotating the arming lever fires the M3A2 arming initiator, locks the shoulder harness inertia reel, releases the drag panel, and exposes the right or left trigger. Gas expansion from the arming initiator fires the M5A2 hatch jettison booster initiator which sends gas pressure to fire the M1A2 hatch jettison thruster, thus jettisoning the hatch. On the gunner seat, the gas expansion from the hatch jettison booster initiator also fires the M3A3 fire control support stowage thruster that, in turn, stows the fire control support. As the hatch is jettisoned, the catapult M3A2 safety pin-pull initiator is fired by means of a telescoping linkage. Gas expansion from the catapult safety pin-pull initiator operates the catapult safety pin-pull cylinder that retracts the safety pin from the M3A2 catapult initiator thus arming the seat. The catapult safety pin-pull cylinder can be operated manually by pulling the manual safety pin-pull lever.

(2) Again, the crewmember's next action is to squeeze the left or right trigger. The motion of the trigger linkage fires the catapult initiator that fires the catapult. and the 0.30-second delay integrated harness release delay initiator.

Firing of the catapult causes the seat, ejectable rails, and intermediate rails to move up the fixed rails. As the seat moves upward, the hinged drag panel rotates downwin:d, the sliding panel extends from the drag panel, and the drogue parachute bridle lines are pulled from their stowage containers. The drag panel and sliding panel rotate downward until the restraint cables become taut.

As the latch mechanisms in the ejectable rails move past the top of the fixed rails, the latches are tripped thus disengaging the ejectable rails from the intermediate rails. The intermediate rails contact the snubbers mounted on the fixed rails and this prevents the intermediate rails from moving upward with the seat and ejectable rails.

As the seat and ejectable rails continue to move upward on the intermediate rails, the drogue parachute lanyard (attached to intermediate rails) becomes taut. The lanyard then releases a latch that attaches the drogue parachute pack to the bottom of the seat. When the bridle lines become taut, the parachute lanyard pulls the parachute pack away from the drogue parachute thus deploying the parachute.

As the seat and ejectable rails move further up on the intermediate rails, the integrated harness release M27 zero delay initiator is fired by means of a trip attached to the intermediate rails.

Gas expansion from the integrated harness release M26 delay and M27 zero delay initiators fires the man-seat separation booster initiator and operates the integrated harness release pin-pull cylinder that releases the integrated harness thus allowing the occupant to leave the seat.

Gas expansion from the man-seat separation booster initiator fires the cartridge in the man-seat separation actuator, tightening the separation harness and throwing the occupant from the seat.

229. Downward ejection system

The downward ejection system provides emergency escape provisions for the navigator and radar navigator by downward ejection of their seats. It is composed of forward facing, downward ejection seats, and the respective escape hatches. Each seat has its ejection system consisting principally of the seat and the hatch immediately underneath. There is no connection between the ejection systems of the seats. Control over the ejection sequence is integral and initiative rests with the individual occupant. Once ejection is initiated, all events are automatic.

Figure 10. Downward Ejection Seats.

Downward ejection seat description. In figure 10, you see that the seats are bucket-type and roller-mounted on fixed ejection rails that allow downward ejection of the seat and occupant. The downward ejection system is provided with single motion ejection seats that require the crewmembers to perform only one operation to complete the ejection sequence. The ejection control handle, located between the occupant's legs, initiates a series of ballistic devices and mechanical linkages incorporated in the seat.

Each seat is equipped with: Ankle restraints. Leg guards. Integrated harness attachment fittings. Personnel parachute. Survival kit. Oxygen and electrical outlets for pressurized suits, headsets, and microphones.

The seat may be adjusted for crew comfort by three electrically controlled actuators that move the seat horizontally or vertically or tilt the seat fore and aft. The ejection controls consist of the leg guards and an ejection control handle located on the forward edge of the seat between the occupant's legs. A safety pin-pull handle provides the occupant with a means of manually arming the catapult initiator in case the catapult safety pin-pull cylinder does not operate during normal ejection procedure. The initiators and the pin-pull cylinder are connected by plastic, metal armored, flexible tubing. The ejection seats are equipped with a drogue parachute that deploys immediately after the seat departs the aircraft. The deployed parachute stabilizes and decelerates the ejection seat to assist in the positive separation of the seat occupant. The drogue parachute pack is supported below the seat by tubular arms which are attached to the seat back. The parachute support is held in position by a pin-pull cylinder. During the seat ejection sequence, the ballistically actuated pin-pull releases the spring-loaded parachute support and as the seat moves down the rails and departs the aircraft, the parachute support arms rotate aft and lock in trail position at the limit of the restraining straps. The drogue parachute ripcord is pulled to deploy the parachute as the support rotates to the trail position. Backup operation of the drogue parachute support release pin-pull cylinder is provided from the integrated harness release 0.3-second delay initiator.

Figure 11. Navigator, Radar Navigator Ejection Sequence.

Ejection sequence. To begin the ejection sequence on the downward seats, the crewmember must pull the ejection control handle (fig. 11). The first part of the control handle travel fires the 1Vi~31A2 arming initiator which sends gas pressure to fire the M16 leg guard thruster, MlA2 hatch jettison thruster, and M5A2 table stowage initiator. Gas expansion from the table stowage initiator fires the M3A3 .table stowage thruster, thus moving the table to the stowed position. Rotation of the leg guards locks the shoulder harness inertia reel.

As the escape hatch is jettisoned, the catapult safety pin-pull M3A2 initiator is fired by means of a link attached to the escape hatch. Gas expansion from the catapult safety pin-pull initiator operates the safety pin-pull cylinder causing it to retract the pin that acts as a safety on the catapult M3A2 initiator..If the catapult safety pin-pull initiator fails to fire when the hatch is jettisoned, pulling the safety pin-pull manual handle operates the safety pin-pull cylinder manually.

The last part of the ejection control handle movement fires the catapult initiator. Gas expansion from the catapult initiator fires the M4A1 catapult and the 0.30-second delay integrated hamess release M26 initiator. Firing of the catapult causes the seat and the ejectable rails to move downward on the fixed rails.

As the seat ejects, the drogue parachute support arm release M27 initiator is fired by means of an initiator trip, which is mounted on the fixed rails. Gas expansion from the drogue parachute support arm release initiator causes the drogue parachute support arm pin-pull cylinder to operate, thus allowing the drogue parachute support to rotate away from the seat. As the parachute support moves away from the seat, the drogue parachute lanyard is pulled from the drogue parachute pack to be turned inside out by spring force resulting in parachute deployment. The drogue parachute support rotates away from the seat until restraint straps become taut.

Gas expansion from the 0.30-second delay integrated hamess release initiator actuates the integrated harness release pin-pull cylinder and fires the man-seat separation actuator. Gas expansion from the integrated harness release initiator also acts as a backup in case the drogue parachute support arm release initiator fails to fire and releases the drogue parachute support.

Actuation of the integrated harness release pin-pull cylinder releases the integrated hamess thus allowing the occupant to leave the seat and it also actuates the gold key retention lock which positively retains the gold key in a latched position. In case the integrated hamess release pin-pull cylinder fails to actuate, there is a mechanical backup. As the drogue parachute support rotates away from the seat, the actuating rings attached to the boom restraint straps are pulled from their mechanisms that mechanically release the integrated harness. Firing of the man-seat separation actuator tightens the separation harness and throws the occupant from the seat.