MIL-DTL-9479E (USAF)
3.4.5.2 Maintainability. The seat system shall require not more than 1 man-hour of maintenance
downtime per flight hour of the aircraft. Maintenance downtime shall be defined by aircraft type
in the acquisition specification and varies according to the aircraft affected. The ejection seat shall
be removable from fighter aircraft without requiring the removal of the aircraft canopy. The seat
system shall be designed to provide the maximum degree of accessibility to components without
removing the seat from the aircraft. Components that shall be accessible and replaceable while the
seat is installed include but are not limited to (see 4.5.1, 4.5.10):
a. Recovery parachute container.
b. Initiators.
c. Survival kit container.
3.4.5.3 Proof loads. Unless otherwise specified, the seat system shall withstand the following
proof loads without permanent deformation (see 4.5.4):
a. Front edge of seat bucket - 270 pounds downward, distributed 1.5 inches each side of
centerline.
b. Armrest - 135 pounds downward, 4 inches aft of forward edge.
c. Ejection controls - 200 pounds tension, center of gripping surface.
d. Headrest - 330 pounds aftward, distributed over 2-inch square area at center of headrest.
e. Seat back - 1,000 pounds aftward, perpendicular to surface, uniformly distributed (below
the headrest).
3.4.5.4 Ultimate loads. Unless otherwise specified, the seat system shall withstand the following
ultimate loads without fracture of materials or failure of attachments (see 4.5.4):
a. Front edge of seat bucket - 400 pounds downward, distributed 1.5 inches each side of
centerline.
b. Armrest - 200 pounds downward, 4 inches aft of forward edge.
c. Ejection controls - 300 pounds tension, center of gripping surface.
d. Headrest - 500 pounds aftward, distributed over 2-inch square area at center of headrest;
40 times the weight of the headrest assembly forward, through the cg of the headrest
assembly.
e. Seat back - 1,500 pounds aftward, perpendicular to surface, uniformly distributed (below
the headrest).
f. Restraint subsystem - 8,600 pounds forward, through the occupant cg; 20° to each side of
forward; and 1,750 pounds downward, through the occupant cg.
g. Seat system - 8,600 pounds plus 40 times the seat system weight forward and 20° to each
side of forward, respectively, through the occupant and seat system combination cg, and
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