the safe-and-arm seat ejection module for use if the lanyard-operated firing mechanism of the module fails. As previously mentioned, during emergency ground egress, seat ejection, or ditching condi- tions, the canopy may be jettisoned by pulling either an internal or external canopy emergency jettison initiator handle. During emergency ground egress, without seat ejection, the explosive signal provided by the canopy jettison initiator is blocked from entering the SMDC lines of the seat ejection system by the one-way explosive transfers. Inert connectors joining the SMDC lines transfer the explosive stimuli through bulkheads, straight runs, tee connections, and 90-degree bends. Explosive manifolds, within SMDC line runs, allow output SMDC lines to be initiated from one SMDC input. This assures system redundancy by providing dual-line initiation for the canopy-separation charge. Canopy Jettison Initiators Two canopy jettison initiators enable the air- crewman to jettison the canopy during emergency conditions, without initiating seat ejection. The canopy may be jettisoned by pulling the canopy emergency jettison initiator handle on either the pilot’s or NFO’s right instrument panel. Canopy External Jettison Initiators Canopy external jettison initiators enable the ground crew to jettison the canopy during ground emergency conditions. Each initiator is manually actuated by pulling its canopy external jettison initiator handle. System and Backup Initiators The system has two system initiators and one backup initiator. One system initiator is located behind each ejection seat. These initiators are actuated by pulling the face curtain or secondary firing control handle. They provide the initial explosive signal for canopy jettison and seat ejection. The backup initiator is on the cockpit turtle deck. This initiator performs a backup function for the safe-and-arm seat ejection module. It is actuated by a lanyard attached to the canopy and the initiator sear linkage. As the canopy is jettisoned, the lanyard actuates linkage to remove the sear and fire the initiator, sending an explosive signal through a 1.1-second time delay to the safe-and-arm module. 2-8 Canopy Gas Generator The canopy gas generator is attached to the lower end of the canopy hydraulic actuator. The canopy gas generator provides high-pressure gas to the actuator, to jettison the canopy. Inert Connectors Inert connectors installed throughout SMDC line runs permit interconnection of the SMDC lines. Explosive Manifolds Explosive manifolds installed within SMDC line runs incorporate an internal explosive crossover that permits either SMDC to fire both output SMDC lines. The manifolds also provide structural support for mounting the SMDC lines to the aircraft structure. One-Way Explosive Transfers One-way explosive transfers installed within SMDC line runs provide unrestricted explosive transfer in one direction only. If an explosive signal is introduced in the opposite direction, it is blocked. SLIDING CANOPY SYSTEM Learning Objective: Recognize the opera- tion, emergency jettison procedures, and components of the sliding canopy system. An example of the sliding canopy system is found on the A-6 aircraft. The A-6 cockpit is covered by a sliding canopy powered by a canopy system consisting of the components required for normal operation and emergency jettison of the canopy. The entire system is hydraulically operated with the exception of the jettison device. The A-6 uses a pneumatic jettison concept. Hydraulic power for operation of the system is furnished by the combined (both engines) hydraulic system or the hand pump system (fig. 2-6). SYSTEM OPERATION Hydraulic flow to open or close the canopy is controlled through a canopy selector valve, which is in the nosewheel well under the cockpit