SHOULDER HARNESS REEL.- The shoulder harness reel (fig. 5-8, view A) is fitted horizontally across the front faces of the main beams and serves as a center crossbeam for the main beams assembly, as well as a means of securing the upper harness. It ensures that the occupant will be brought to, and locked in, the correct posture for ejection. For normal flight operations, the shoulder harness is free to extend and retract as the occupant moves in the ejection seat. The shoulder harness control lever on the LH side of the seat bucket can be moved to the forward (locked) position, which will permit the

Figure 5-8.-View A, shoulder harness reel; view B, shoulder harness reel, sectioned view. 5-9

harness straps to retract but prevent them from extending. When in the normal unlocked state, automatic locks protect the occupant against rapid forward movement under high g-loading.

PARACHUTE DEPLOYMENT ROCKET MOTOR MK 122 MOD 0.- The parachute deployment rocket motor (PDRM) (fig. 5-9) is mounted on the LH main beam of the seat. When initiated by the sequencer, restraint release unit, or manual override (MOR) system, the PDRM extracts the personnel parachute from its stowage by means of a withdrawal line attached to the deployment sleeve.

The PDRM is a sealed unit. It consists of a cylindrical body that contains a gas-operated secondary cartridge in a breech at the lower end and a rocket with an integral gas-operated igniter cartridge in a barrel at the upper end. In a parallel connected chamber is an electrically initiated primary cartridge. A gas inlet is connected by a gas pipe to the harness release system.

Figure 5-9.-Parachute deployment rocket motor (Mk 122Mod 0).

Fitted around the rocket is a sliding stirrup, which is connected to the parachute withdrawal line and is free to slide down the rocket as it leaves the barrel.

ELECTRONIC SEQUENCER.- The NACES sequencer assembly (fig. 5-10) is composed of the sequencer, connectors to the interface with pitot static and dynamic pressure sources, and cable loom sleeving. It is mounted across the main beam assembly, below the parachute assembly. Upon activation, the sequencer determines the ejection mode and controls the functions of the drogue release, parachute deployment, and seat/man separation.