外流活门/安全释压活门
1 Introduction
The aft outflow valve controls the air flow out of the airplane fuselage. The valve is below the fuselage near the aft entry door. When ground unpressurized, the outflow valve moves full open.
The forward outflow valve is located at the forward left side of the forward cargo compartment, in the E/E compartment. The forward outflow valve is a component of the cargo heating system and does not affect the cabin pressurization control system. This is assured by an electrical circuit that closes the forward outflow valve whenever the cabin pressurization outflow valve is nearly closed. There is a limit switch installed in each actuator of the cabin pressurization outflow valve. The forward outflow valve will close when the cabin pressurization outflow valve is within 0.5 degrees of closed and will open when the pressurization outflow valve opens approximately 4.5 degrees. An electrical circuit also closes the forward outflow valve any time the cabin air recirculation fan is operating.
Two safety relief valves acting independently of each other and all other systems prevent the cabin-to-ambient pressure differential from exceeding 8.50 psi. The safety relief valves are installed under the fuselage approximately below the aft right service door. One safety relief valve is installed on each side of the outflow valve.
The pressure and relief valve is a spring-loaded flapper valve. The valve will open when the ambient pressure is approximately 1.0 psi more than the cabin pressure. This relief valve is located on the aft right side of the aircraft above the upper safety relief valve .
2 Ref: AMM21-31 AMM21-32
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