providing redundant ignition to the catapult
As the seat catapult fires, the gas pres-
sure forces locking pistons in the catapult
tubes to disengage the locking balls, which
unlock the inner- and outer catapult tubes.
As the seat and outer catapult tubes move
upward, the pilots legs are drawn against
the front of the seat by the leg restraint
mechanism. Simultaneously, the quick-disconnect
fittings for pilot services are separated, and
a lanyard on the catapult manifold activates the
emergency oxygen bottle, IFF, and AN/URT-33
emergency radio beacon.
After approximately 16 inches of seat
travel, gas pressure is applied to the drogue
gun pistons housed in the catapult tubes.
These pistons forcibly expel the drogue para-
chute container for quick drogue parachute
deployment. The drogue parachute provides
seat stability and aids in withdrawing the main
After approximately 31 inches of seat travel,
gas pressure is ported to a thruster (pin puller),
a 3-second time-delay initiator, a multiple time-
delay (0.1- and 1.3-seconds) initiator, and the
igniters of the two seat-back rocket (SBR) motors.
The SBRs produce the thrust necessary for the seat
and pilot to attain sufficient terrain and aircraft
tail clearance to permit parachute deployment.
The necessary thrust is available even at zero
airspeed and zero altitude.
Upon ejection, the seat is stabilized by a
Directional Automatic Realignment of Trajectory
(DART) system. Two lanyards, attached to the
aircraft and feeding through tension brake
assemblies beneath the seat, counteract excessive
pitch and roll.
The post-ejection sequencing system for
deploying the Wind Oriented Rocket Deployment
(WORD) motor and drogue release mechanism
follows one of four automatic ejection modes,
depending on the aircrafts airspeed and altitude.
These modes of operation will be discussed later
in this chapter. Depending on the mode of
operation, the time-delay initiators fire, directing
gas pressure to actuate the WORD motor and
drogue release mechanism, and arm the aneroid-
Upon actuation, the WORD motor/drogue
release disconnects the WORD rocket motor.
This allows the wind resistance on the drogue
chute to withdraw the WORD motor from
the seat. When the WORD rocket motor
arming cable is withdrawn, it releases the
firing pin and ignites the rocket. Depend-
ing on the mode of operation, the aneroid-
actuated initiator fires. This activates the
personnel parachute container opener, releas-
ing the personnel parachute. The parachute
will be withdrawn by either the WORD rocket
motor, drogue parachute, or internal pilot
When the personnel parachute suspension
lines and risers become taut, a firing lanyard
attached to a ballistic spreading gun extracts
the spreading gun firing pin sear. The re-
leased firing pin strikes and activates a spread-
ing-gun ballistic charge, which expels metal
slugs in a 360-degree pattern. The slugs,
attached to parachute suspension lines, rapidly
inflate the canopy during very low-speed
ejection. During high-speed ejection, the air-
stream energy far exceeds that of the spread-
ing gun. Therefore, the gun has little effect
on parachute inflation time.
As wind resistance acts on the personnel
parachute, tension on the seat and man release
lanyards actuates the seat and man separation
initiator to produce gas pressure directed to the
guillotine. The guillotine severs both inertia reel
straps and releases the pilots upper torso.
Simultaneous actuation of seat and man separa-
tion mechanical linkage by the lanyards releases
the survival kit assembly and pilot from the
The pilot may release the survival package
in the survival kit by pulling a handle located
near his right hip. After the package drops
12 feet, a snubbing lanyard initiates inflation
of the life raft. The remainder of the survival
package drops an additional 13 feet and hangs
below the life raft to stabilize it during
Ejection Mode Sequences
The Stencel seat is equipped with a mode
sequencing system that controls four automatic