Electrically Actuated Canopy Pressure Seal Regulator Valve

Electrically Actuated Canopy Seal An electrically actuated canopy pressure seal system is shown in figure 2-11. This type of system is controlled by a pressure regulator and dump valve assembly, which consists of a pressure regulator, a solenoid poppet shutoff and vent valve, and a relief valve. Electrically Actuated Canopy Pressure Seal Regulator Valve The canopy pressure seal regulator valve controls the pressurizing and depressurizing of the canopy seal, depending upon the canopy position. The pressure regulator consists of a spring-loaded diaphragm, which controls a poppet valve to admit the correct air pressure to the canopy seal. An adjustment screw is provided at the top of the regulator housing to adjust the output of air pressure. The shutoff and dump valve consists of a solenoid-operated poppet valve, which is spring- loaded to the closed position. When the solenoid is energized (fig. 2-11, view A), the dump valve closes the vent port and opens the regulator shutoff to permit inflation of the canopy seal. The outlet pressure is maintained at approximately 20 psi by the pressure regulator. When the solenoid is de-energized by the opening of the canopy (fig. 2-11, view B), the dump valve opens the vent port, closes the regulator shutoff to stop the flow of supply air, and dumps the pressure in the canopy seal over- board through the vent line. The relief valve feature of the pressure regulator prevents seal pressure from becoming excessive during rapid altitude changes by venting the seal pressure over- board when the pressure reaches a maximum of 22 psi (fig. 2-11, view C). In case of an electrical failure, the reg- ulator valve is spring-loaded in the dump position. Ground Test Connections Most canopy pressure seal systems have ground test connections that are used to ground test the system and to pressurize the system during carrier deck storage. The Figure 2-12.—Cabin air pressure test panel. ground test connections (fig. 2-12) are usually located on the cabin air pressure test panel. One connection is used for ground test, and the other, which is normally the seal vent, is used for ground pressurization of the canopy seal. MAINTENANCE Maintenance of the canopy system consists of servicing, troubleshooting, and removal and installation of components. The applicable air- craft maintenance instructions manual (MIM) furnishes such information as proper procedure, manpower requirements, materials lists, tool and equipment lists, quality assurance instructions, and maintenance-level instructions for the disposi- tion of defective parts. Servicing Servicing is limited to cleaning the canopy seal, ground inflating the canopy seal, and periodic inspections for visible defects, dirt, and foreign material accumulations. All major components of the system are self-sustaining and require no general servicing between overhaul periods for normal operation. When pressurized aircraft are stowed on the carrier flight deck without canopy covers, the canopy seal should be inflated externally to protect the cabin area. Ground pressurization of the canopy seal is accomplished by attaching an external air source to the canopy seal vent and ground pressurization connection 2-15