MIL-DTL-9479E (USAF)
3.2.13.3 Ground safety device. The seat system shall be protected against inadvertent actuation
on the ground by a single safety device. The safety device shall positively lock all controls in the
stowed position. The linkage between ejection controls and system initiators shall be designed so
that when the controls are safetied, application of force to the linkage will not actuate the system.
Additional ground safety devices shall be provided for protection during maintenance activities,
but they shall be interconnected and located so they cannot remain installed when the aircraft is
ready for flight. Streamers on the safety devices shall be provided in accordance with drawing
67D34391 (see 4.5.1).
3.2.13.4 Canopy and hatch removal. The seat system shall include provisions for positive,
immediate removal of the aircraft canopy and hatch (see 4.5.1).
3.2.13.5 Ejection through the canopy. The ejection controls and initiation subsystem shall be
designed to permit automatic ejection of the seat assembly through the canopy in the event the
canopy jettison mechanism malfunctions. On those aircraft where ejection through the canopy is
not permitted because of hatch or canopy construction, means shall be provided to prevent firing
of the rocket catapult until the hatch or canopy has been jettisoned (see 4.5.1, 4.5.7).
3.2.13.6 Ejection sequencing subsystem. For a multi-crew aircraft requiring an ejection seat
system, an ejection sequencing subsystem shall be provided. The sequencing subsystem shall be
initiated by the command pilot as a pre-ejection function but shall not prevent the other crew
member(s) from initiating their own ejection. The sequencing subsystem shall be designed to
jettison canopies and eject the seat-man combinations in a manner to (see 4.4.2 c., 4.5.5):
a. Provide protection for personnel from the rocket-catapult heat and blast effects.
b. Ensure the escape of all crew members in minimum time (see 6.2).
c. Preclude collisions between jettisoned canopies and ejected seat-man combinations.
d. Preclude collisions between ejected seat-man combinations.
In training aircraft, the sequencing subsystem shall provide a means for the instructor pilot to
initiate the ejection for both crewmen from either ejection seat position. Particular attention shall
be directed toward ensuring minimum time between ejection initiation and separation of the last
crew member from the aircraft.
3.2.14 Actuation subsystem. All propellant-actuated devices and cartridge-actuated devices shall
conform to MIL-C-83125 and shall be approved by the procuring activity prior to installation.
The energy required for activation of mechanical or propulsion links may be transmitted either by
transmission hose, detonating transmission lines, electrical lines, or fiber-optic cable. Ballistic gas
transmission hose shall conform to the -4 configuration of MIL-H-25579. The ballistic gas
transmission hose and fittings shall provide free flow in accordance with the design schematic of
the ballistic subsystem (see 4.4.1 b., 4.5.3).
3.2.15 Propulsion subsystem. The seat system shall be provided with a propulsion subsystem
with sufficient impulse to ensure aircraft tail clearance throughout the aircraft performance
envelope and, in conjunction with the parachute recovery system, provide recovery from high
sink-rate conditions. If a rocket catapult subsystem is used, it shall conform to MIL-C-83124 and
shall be approved by the procuring activity prior to installation. The catapult action shall be
aligned within 5° of the seat assembly back angle. The thrust shall be as defined by the center-of-
gravity (cg) envelope (4.5.8).
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