MH-S-655 lA(USAF)
3.2. 13 Leg braces. Retractable leg braces shall be provided on the seat to laterally brace the legs on the outboard side during ejection. They shall
be located substantially as shown on Figure 1 and shall be interconnected
to move into position simultaneously. The leg braces may perform the ftm.ctions of pre-ejection controls in that the motion of raising the leg braces may be utilized to perform such functions as releasing cabin or cockpit pressure, stowing the control column, etc. The leg braces shall be faired in to eliminate the possibility of fouling the crew members personal equipment and/or clothing upon separation from the seat after ejection.
3.2.14 Ejection or emergency controls. Ejection controls shall be incorD
porated in the leg braces at the sides of the seat and in an ejection
ring to be located on the forward edge of the seat as shown in Figure 2.
To ensure that the ejection ring will be within reach of the occupant when seated in the ejection position, the design shall be such that the upper gripping surface shall automatically extend upward three inches above the edge of the seat when the leg braces are moved into the locked position.
3.2.14.1 Sequence "A" - seat bottomed prior to ejection. The first moveD ment of the leg braces shall cause the seat to move to the bottom position. When the seat has reached the bottom position, it shall then be possible to pull the leg braces into the locked position. This motion shall lock the shoulder harness take-up reel. Pulling the ejection ring shall perform the following operations: 1. Jettison the escape hatch. 2. Fire the catapult initiator which in turn fires the catapult. It shall not be possible to perform the second operation until the escape hatch has been jettisoned.
This shall be accomplished by an interconnection between the hatch and the
initiator safety pin which shall provide for the removal of the initiator safety pin when the hatch is jettisoned.
3.2.14.2 Sequence "B" - seat ejectable from any position. Movement of the leg braces into a locked position shall lock the shoulder harness take-up reel. Pulling the ejection ring shall perform the following operations:
1. Jettison the escape hatch. 2. Fire the catapult initiator which in turn fires the catapult. It shall not be possible to perform the second operation tm.til the escape hatch has been jettisoned. This shall be accomplished by an interconnection between the hatch and the initiator safety pin which shall provide for the removal of the initiator safety pin when the hatch is jettisoned.
3.2.14.3 The ejection controls shall be so designed that it shall not be possible to pull the ejection ring unless the leg braces have first been moved into the locked position. Movement of the ejection ring to accomplish firing shall be kept to a minimum, not to exceed two inches, and shall be restrained from further movement after the initiator has been fired. A maximum of 40 pounds force applied to the ejection ring shall perform the operations noted in paragraph 3.2.14.1 or paragraph 3.2.14.2.
3.2.14.4 Catapult initiator. The purpose of the initiator is to reduce the complexity of the controls between the ejection ring and the catapult. Application of .75 inches of motion to the initiator firing pin is required to fire the initiator cartridge. Firing of the initiator supplies gas
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