The SJU-5/ A ejection seat system (fig. 6-20) provides support for the pilot during normal flight conditions and a method of escape from the air-craft during emergency conditions. Selected seat system components are discussed in the follow-ing paragraphs and keyed to figure 6-20.

Catapult

The catapult (3) is a cartridge-actuated device that provides the initial force required to eject the seat from the aircraft. The catapult is located within the main beam assembly (6) and is attached to the bulkhead of the cockpit by two mounting lugs. The ejection seat is installed on the catapult with three pairs of slippers located on the inboard side of the main beam assembly. The main beam assembly fits into catapult guide rails located on the outboard sides of the catapult's outer barrel. The ejection seat is locked to the catapult by the top latch mechanism. The catapult consists of three major parts: the inner barrel, the intermediate barrel, and the outer barrel.

INNER BARREL.- A neck-shaped piston head, fitted with a set of expander and piston rings, is attached to the lower end of the inner barrel to provide a gas seal with the intermediate barrel. A breech is located at the upper end of the inner barrel for the primary firing mechanism and cartridge. The breech has a groove on the out-side edge into which the plunger of the top latch mechanism of the ejection seat is engaged.

INTERMEDIATE BARREL.- The inter-mediate barrel is located between the inner barrel and the outer barrel. The intermediate barrel increases the length of catapult extension. It also restrains bending loads incurred during ejection. A piston head fitted with two sets of six expander and piston rings is attached to the lower end. The piston head serves as a gas seal between the intermediate barrel and the outer barrel. A guide bushing is riveted to the upper end of the intermediate barrel to keep the inner barrel steady during extension. The guide bushing rivets are sheared by the neck-shaped piston head of the inner barrel during ejection. This allows separa-tion of the inner and intermediate barrels. Twelve pressure rings are installed on the intermediate barrel to absorb the inertia forces encountered during barrel separation.

OUTER BARREL.- The outer barrel houses the intermediate and inner barrel assemblies. Two breeches are located on the aft side to accept the auxiliary cartridges. Two guide rails are bolted on the outboard sides of the outer barrel. The lower end is used to attach the catapult to the aircraft. The upper end has a square aperture to engage the plunger of the top latch mechanism. The upper fitting is threaded for the guide bushing that retains the intermediate barrel. The guide bushing is locked in place by a dowel screw.

Figure 6-20.- Martin-Baker SJU-5/ A ejection seat.