aft to rotate the actuating mechanism bell crank(s) that fires the initiator(s). M99 INITIATOR ACTUATING MECH- ANISM.— The actuating mechanism is located between the guide rails, and is attached to the upper section of each canted bulkhead, behind each crew member’s seat. The actuating mechan- ism for the forward seats have dual bell cranks (striker plates) and clevises to actuate the two M99 initiators installed on each side of the actuating mechanism. Since each aft seat requires one M99 initiator for the ejection sequence, the actuating mechanism is a single bell crank and clevis arrangement. During the seat ejection sequence, the seat-mounted firing rods are moved aft to rotate the actuating mechanism bell crank(s) and clevis(es) to fire the M99 initiator(s). Refer to figure 6-6 while reading the follow- ing text. M53 INITIATOR.— There are thirteen M53 initiators installed in aircraft-attached ejection seat plumbing. Eleven of the M53 initiators are installed between the guide rails, and two initiators are installed at flight station (FS) 263 (one each at the INCOS tray thruster location). Each pilot and copilot location has four M53 initiators; the TACCO location has one; and the SENSO station has two. The M53 initiator is a cartridge-actuated, gas-producing device triggered by gas pressure from a remote source. The M53 initiator consists of a constant-volume cylinder with a tube connection at one end and a gas-operated firing mechanism and cartridge. In the ejection seat sequence, gas pressure from the M99 initiator(s) actuates the M53 initiators. M53 initiators characteristically serve as line-boosters in the ejection seat system to counteract rapid pressure decay caused by tubing length. PRESSURE-ACTUATED 0.3-SECOND DELAY INITIATOR.— Seven 0.3-second delay initiators are installed between the guide rails. Two 0.3-second delay initiators are installed at the pilot’s, the copilot’s, and the SENSO station; and one is installed at the TACCO station. At the pilot’s and copilot’s stations, an Mk 11 MOD 0 initiator is installed on the 0.3-second delay initiator. The 0.3-second delay initiator is a pressure-actuated device with a conventional firing piston secured in the cocked position by a shear pin. In the ejection sequence, the 0.3-second delay initiators are used as time delays in the inertia reel shoulder harness retraction, in the INCOS trays retraction, and in the group or solo ejection sequencing of crew members in the firing of the rocket catapult(s). MK 11 MOD 0 INITIATOR.— A MK 11 MOD 0 initiator is installed below the floor line directly under the rocket catapult at the pilot and copilot seat locations. Each MK 11 MOD 0 initiator is installed on the 0.3-second delay initiator, and both fire into the rocket catapult. The MK 11 MOD 0 initiator is a cartridge- actuated device triggered by gas pressure from a remote source. In the ejection sequence, the MK 11 MOD 0 initiators are used as time delays in the group-ejection (all seats) mode to allow the two aft seats to eject 0.5 second before the front seats to permit proper spacing of personnel for safe parachute deployment and landing. PLUMBING AND CHECK VALVES.— Most plumbing for the aircraft-attached ejection seat components is flexible hose-type plumbing located between the guide rails. There are a minimum of lines between the forward and aft seats and the INCOS tray thrusters. There are twenty check valves installed in aircraft-attached ejection seat components; all are located between the guide rails. In the ejection sequence, the check valves allow the correct group or solo-ejection selection to occur. INCOS TRAY THRUSTER.— At both the TACCO and SENSO locations, a thruster is installed to retract the respective INCOS trays during the seat ejection sequence. The thruster is a pressure/percussion device that employs sear pins, firing pins, and primers to ignite the main charge. In the ejection sequence, the INCOS tray is retracted at the same time that the inertia reel shoulder harness retraction occurs. EJECT MODE SELECTOR VALVE.— A selector valve is installed on each inboard guide rail in the flight station. The selector valve consists of a beam assembly with a switch and handle and the valve body. The selector valve routes high-pressure gas from the M99 initiators to the aircraft sequencing system, depending on the selected position (GROUP EJECT or SELF EJECT) of the selector valve. When the pilot’s or copilot’s selector valve handle is in the down or GROUP EJECT position, an electrical ground is completed, which causes the GROUP EJECT indicators to come on at the SENSO and TACCO instrument panels. When either selector valve handle is in the up or SELF EJECT position and the aircraft altitude is less than 15,000 feet, the altitude sensor switch cause the indicator 6-10