MIL-DTL-9479E (USAF)
3.2.10 Ejection rails. A set of ejection rails and rollers (or slide blocks) shall be furnished with
the seat assembly. The rails shall be designed to be installed parallel to the seat back and shall be
sufficiently rigid to prevent deflection which would cause binding of the rollers (or slide blocks) or
allow the rollers to jump the rails. The rails and rollers (or slide blocks) shall be designed to
provide maximum guided catapult stroke in the aircraft during ejection. The ejection rails and
rollers (or slide blocks) shall be such that the friction produced between the rails and rollers (or
slide blocks), as a result of the airload on the seat during ejection, will be held to a minimum.
Provisions shall be made to prevent foreign objects from becoming lodged between the rollers (or
slide blocks) and the rails, consistent with ease of seat installation. The rails and rollers (or slide
blocks) shall retain the seat and crewman combination under all ditching and crash loads (see
4.4.1 a, 4.5.1).
3.2.11 Personal restraint subsystem. The seat system shall incorporate a personal restraint
subsystem that will provide full upper and lower torso restraint and control, and shall not decrease
crew member efficiency nor cause more than a minimum of restriction to movement during
normal flight. The restraint attachments shall be designed to provide sufficient structural integrity
for positive crew member protection without injury under all conditions of emergency ejection,
ditching, and crash impact. Torso restraint shall be provided through use of an integrated torso
harness. The torso harness shall include provisions for attaching personal parachute risers and the
survival kit. Depending upon system design, it may also contain provisions for attaching lap
straps from the seat in lieu of using a separate lap belt assembly. In cases where lap straps are
used, the attachment to the torso harness shall be designed to prevent any movement or
submarining of the seat occupant because of ejection, ditching, or crash accelerations (see 4.5.1,
4.5.6.11).
3.2.11.1 Upper torso restraint. The seat system shall incorporate an inertia reel mechanism
conforming to MIL-R-8236, with additional requirements for powered retraction. The manual
inertia lock reel control shall be located on the left side of the seat assembly with easy access by
the seat occupant. The inertia reel mechanism shall include powered retraction provisions to
automatically position and restrain the seat occupant against the backrest of the seat as a pre-
ejection function. The powered retraction provisions shall be capable of positioning the seat
occupant through 0 to 18 inches of travel and taking a load up to 300 pounds within 0.3 seconds
maximum at 70°F (0.4 seconds maximum at -65°F). The reel-in velocity shall be limited to a
mean of 9 feet per second with a standard deviation of 1 foot per second. The maximum total
load applied to the seat occupant after the reel has positioned the occupant shall not exceed 100
pounds (see 4.5.1, 4.5.6.11).
3.2.11.2 Inertia reel strap bearing point. The inertia reel strap shall be located so that, when in
the fully restrained position, no compression loads will be transferred to the seat occupant's spinal
column. This shall be based upon a 95th-percentile sitting shoulder height (see 4.5.1, 4.5.6.11).
3.2.11.3 Lower torso restraint. The seat system shall incorporate provisions for lower torso
restraint through the use of either a lap belt assembly or lap straps that attach from the seat
assembly to the torso harness. In either case, the seat attachment points shall be located on a line
in the side view which is 45° to the seat bucket bottom and through the seat reference point (this
line is shown in figure 1 labeled as the "Lap Strap Attachment Line"). In systems designed to
incorporate lap straps, the survival kit retention straps shall be permanently attached to the lap
straps so that the survival kit actuator handle is clear for easy access by the crew member at all
times during parachute descent prior to kit actuation (see 4.5.1, 4.5.6.11).
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