FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsMedium
During a pressurization system inspection, a technician is asked to identify the component that primarily regulates cabin pressure by controlling the rate of air discharged overboard from the pressurized fuselage.
- ABleed air shutoff valve
- BCabin air compressor
- CSafety relief valve
- DOutflow valve
Show answer & explanationAnswer & explanation
Correct answer: D. Outflow valve
The outflow valve modulates the amount of conditioned air leaving the pressurized cabin to maintain the desired cabin pressure schedule; the cabin pressure controller signals the outflow valve to open or close as needed.
Why the other options are wrong
- A. Bleed air shutoff valves control air source to the system, not cabin pressure regulation.
- B. The compressor (or bleed air) supplies air into the cabin, it does not control outflow.
- C. The safety/relief valve only opens to prevent overpressure, it isn't the primary regulator.
Outflow Valve
A pneumatically or electrically controlled valve that regulates the rate of air leaving a pressurized cabin to maintain a scheduled cabin altitude.
- Positioned by the cabin pressure controller
- Modulates continuously during flight
- Works with a separate safety relief valve for overpressure protection
Memory trick: Outflow valve is the cabin's exhaust throttle.