FAA Commercial Pilot Airplane (CAX)Aircraft SystemsMedium
What is the primary function of the outflow valve in an aircraft cabin pressurization system?
- AIt regulates the amount of bleed air entering the cabin from the turbocharger or engine compressor
- BIt limits manifold pressure to prevent engine overboost during climb
- CIt automatically extends the landing gear if cabin pressure is lost
- DIt controls the rate at which conditioned air exits the cabin, thereby maintaining the desired cabin pressure differential
Show answer & explanationAnswer & explanation
Correct answer: D. It controls the rate at which conditioned air exits the cabin, thereby maintaining the desired cabin pressure differential
The outflow valve, typically controlled by a cabin pressure controller, modulates how quickly air leaves the cabin. By restricting or allowing outflow, it sets the cabin pressure differential and rate of cabin altitude change, working opposite to the air inflow from the compressor/turbocharger.
Why the other options are wrong
- A. Regulating incoming bleed air is a different function performed by inflow/bleed valves, not the outflow valve.
- B. Manifold pressure limiting is a turbocharger wastegate function, not pressurization.
- C. Gear extension is unrelated to pressurization system components.
Outflow Valve
A cabin pressurization component that controls the rate air leaves the cabin, setting cabin pressure differential and cabin altitude.
- Works with inflow (bleed) air to balance cabin pressure
- Usually electronically or pneumatically controlled
- Malfunction can cause rapid decompression or overpressurization
Memory trick: Air comes in from the engine, leaves through the outflow door.