MIL-S-655 lA(USAF)
3.3.3 Strength requirement. The crew ejection seat shall have sufficient strength to carry the following loads:
3.3.3.1 Personnel catapult load. A load of 4300 pounds ultimate, 2850 pounds proof shall be applied upward parallel to the centerline of the rollers and through the combined center of gravity of the seat and pilot. The load shall be applied to the safety belt and the tiedown strap. (In determining the above combined center of gravity, the center of gravity of the pilot may be considered as being nine inches from the top of the survival kit and 11.5 inches from the forward face of the parachute). If the seat is required to be bottomed prior to ejection, the seat shall be adjusted to the down (ejection) position during this test. If the seat is ejected from any position, it shall be adjusted to the high forward
position where diagonal adjustment is required.
3.3.3.2 Front edge. The seat shall withstand a load of 400 pounds ultimate,
270 pounds proof, applied to the top front edge of the seat bottom over a
length extending 1-1/2 inches to each side of the center of the seat, with
the seat bottom horizontal.
3.3.3.3 Ejection ring. The ejection ring and the connecting controls to the initiator firing pin shall withstand a load of 350 pounds ultimate.
3.3.3.4 Parachute support ledge. The parachute support ledge shall withD stand a load of 400 pounds ultimate, 270 pounds proof, distributed over an area extending four inches to either side of the center of the seat and
applied perpendicular to the upper surface of the support edge.
3.3.3.5 Leg braces. Each of the leg braces shall be capable of withstanding a side load of 500 pounds ultimate, 330 pounds proof, applied outward perpendicular to the leg brace and distributed over that portion of the leg brace that would be contacted by the leg of the crew member during ejection.
3.3.3.6 Foot retainer. A load of 275 pounds ultimate, 180 pounds proof, shall be applied upward and parallel to the center line of the rollers equally distributed over the contact surfaces of each foot retainer.
3.3.3.7 Head rest. A load of 500 pounds ultimate, 330 pounds proof, shall be applied aft in a direction parallel to the seat bottom equally
distributed over an area of 2 inches square at the center of the head rest.
3.3.3.8 Crash loads.
3.3.3.8.1 Forward. A load of 5,760 pounds ultimate, 3,840 pounds proof, shall be applied to the lap belt mou+tings on the side of the seat in a direction inclined 40 degrees up from the bottom of the seat. A load of
2,400 pounds ultimate, 1,600 pounds proof, shall be applied to the tiedown
strap, in an upward direction, perpendicular to the seat bottom (pan). A load of 3,600 pounds ultimate, 2,400 pounds proof, shall be applied to the shoulder harness take-up reel, in the unlocked extended position, in a forward direction parallel to the seat bottom over the shoulder harness support structure. These loads shall be applied simultaneously and the seat shall be adjusted to the mid-position during this test.
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