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

Figure 2-6.- Hydraulic canopy operation.

floor. This selector valve may be operated either electrically or manually from the cockpit or the nosewheel well. Normal operation is electrical through the canopy switch on the pilot's instru-ment panel. This switch controls the selector valve whenever the engines are operating or whenever external electrical and hydraulic power is applied to the aircraft. Manual opening of the canopy is conducted using a hand pump system that pumps the canopy into position when combined hydraulic system power is not available on the aircraft. The hand pump is in the nosewheel well and can be operated either from there or from the cockpit.

When the selector valve closes, hydraulic pressure from either the combined hydraulic system or the hand pump system flows through the selector valve into the canopy close line.

Pressure in this line is delivered through a flow regulator to the rod end of the canopy actuating cylinder, causing the piston and rod to retract and close the canopy. Opening of the canopy is the reverse of the closing operation. NOTE: Maintenance of the hydraulic portion of the A-6 canopy actuation system is the responsibility of the AMH rating.