SYSTEM OPERATION

aircraft structure to maintain cockpit pres- surization. The system, using cooled engine bleed air from the air-conditioning system, inflates the canopy seal in response to movement of the canopy locking linkage. The system deflates the seal when the can- opy is unlocked. There are many different types/designs of pressure-maintaining seals used on naval aircraft. The main difference between canopy seal systems is the type of canopy seal pressure regulator used, elec- trical or mechanical. The F-14 inflatable seal will be discussed in the following para- graphs. The A-6 operates in a similar man- ner, but will not be covered in detail here. Refer to maintenance manuals for specifics. SYSTEM OPERATION The canopy seal pressure regulator receives cooled engine bleed air, at approximately 80 psi, from the service air heat exchanger. When the canopy is closed and locked, the regulator plunger is released; this opens the shutoff valve. Air from the regulator inlet then flows past the check valve and shutoff valve, through the outlet port, and to the canopy inflatable seal. As air pressure in the seal increases, pressure buildup in the regulator chamber moves the bellows seat away from the flange. The interior of the bellows is vented to ambient. When pressure in the seal reaches 25±5 psi above ambient, the bellows will Figure 2-9.—Typical canopy inflatable seal (removed). 2-12