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).

have moved sufficiently to seat the shutoff valve and stop flow through the regulator. The inflated seal then fills the gap between the canopy frame and the mating aircraft structure, preventing loss of cockpit pressure. If pressure downstream of the regulator in-creases to 6 to 8 psi above the regulated pressure, additional bellows movement causes the relief valve stem to unseat the ball in the seat to vent the excess pressure through the relief/ vent port. The check valve prevents loss of pressure from the inflatable seal should the air supply to the system fail. When the canopy is unlocked, the regulator plunger is depressed. The plunger moves the bellows seat toward the relief valve stem to close the shutoff valve and unseat the ball, venting downsteam pressure through the relief/ vent port. The components of the canopy seal system are discussed in the following paragraphs.