emergency oxygen system is automatically activated during ejection by a lanyard connected to the cockpit floor. An oxygen/communications hose is connected to unions on the LH rear top of the lid assembly, and provides connections between the seat occupant and the aircraft and survival kit systems. RADIO LOCATOR BEACON.— A URT- 33A radio locator beacon is located in a cutout in the left thigh support. The beacon is actuated during ejection by a lanyard connected to a common anchorage point with the emergency oxygen lanyard. RUCKSACK ASSEMBLY.— The rucksack assembly is attached to the underside of the lid assembly by five fabric straps and a double cone and pin release system. The rucksack contains a life raft and the survival aids. Yellow manual deployment handles mounted on the kit enable the occupant to deploy the rucksack and contents onto a lowering line after seat/man separation. The LRU-23/P life raft inflates automatically on rucksack assembly deployment. COMPONENT OPERATION The operation of each component and subsystem is discussed in the following paragraphs. The operation of the system as a whole is discussed later in the chapter. Catapult Assembly Explosive charges are contained in an ejection gun initiator, JAU-56/A (figs. 5-3 and 5-4), and a secondary cartridge. Gas pressure from the seat firing system or the aircraft command sequencing system operates twin firing pins in the ejection gun initiator to fire the explosive charge. Gas enters the manifold valve through one or both of the inlet ports, depresses the check valves, and passes down through the vertical bore into the initiator. Gas pressure acts upon the twin firing pins in the initiator, shearing the shear pins and forcing the firing pins down to strike the percussion caps and ignite the explosive filling. The gas pressure generated within the catapult— 1. Passes to the ballistic latches to operate the pistons, which retain the multipurpose initiator static lanyards. 2. Propels the catapult piston upwards. The initial movement of the piston forces the spring-loaded top latch plunger out of the breech groove back into the barrel latch (fig. 5-4). The piston continues to rise, thrusting against the top crossbeam of the seat, the upward movement causing the shaped end of the top latch plunger to ride out of, and disengage from, the barrel latch. Further upward movement of the piston uncovers the secondary cartridge, which is fired by the pressure and heat of the initiator gas. After approximately 38 inches (965mm) of travel, the piston head strikes the guide bushing and shears the three dowel screws. After a further 4 inches (101mm) of travel, the piston separates from the barrel and moves away with the ejected seat. Main Beams Assembly The main beams assembly supports the major components of the ejection seat. The operation of the components supported by the main beams assembly is discussed in the following paragraphs. SHOULDER HARNESS CONTROL SYS- TEM.— When the ejection control handle is pulled, gas from the RH seat initiation system is piped into the breech to operate the cartridge. The gas also passes to the operating piston in the governor housing, forcing it upwards to operate the trip lever and bring the locking pawl into contact with the ratchet wheel. The gas from the impulse cartridge in the breech impinges on the end of the piston forcing it along the cylinder. Horizontal movement of the piston is transmitted via the threaded drive screw to rotate the splined shaft, spool assemblies, and ratchet wheel, which winds in the webbing straps to pull back and restrain the occupant’s shoulders. The engaged locking pawl locks the spools in the restrained position. Withdrawal of the webbing straps at excessive speed causes the two governor pawls to rotate outwards under centrifugal force and engage the teeth on the housing, preventing rotation of the splined shaft and spool assemblies and further withdrawal of the straps. This system prevents the occupant from being thrown forward on crash landing or sudden deceleration if the shoulder harness control lever is in the disengaged position. Easing of tension on the webbing straps allows the pawl springs to reassert themselves and disengage the pawls from the teeth, permitting free withdrawal of the straps again. PARACHUTE DEPLOYMENT ROCKET MOTOR.— Upon seat ejection, gas pressure from 5-26