FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsMedium
A technician is testing the cabin pressurization system of a transport-category aircraft and observes that the pressurization controller automatically repositions the outflow valve as the aircraft climbs. What is the primary function of the pressurization controller?
- ASupply conditioned bleed air to the cabin distribution manifold
- BDetect rapid decompression and sound the master warning
- CPrevent structural damage by limiting maximum differential pressure only
- DMaintain a preset cabin altitude schedule relative to aircraft altitude
Show answer & explanationAnswer & explanation
Correct answer: D. Maintain a preset cabin altitude schedule relative to aircraft altitude
The pressurization controller schedules cabin altitude as a function of aircraft altitude and modulates the outflow valve to follow that schedule, keeping cabin altitude lower than actual flight altitude for passenger comfort.
Why the other options are wrong
- A. Bleed air conditioning is handled by the air conditioning packs, not the pressurization controller.
- B. Decompression warnings come from a separate cabin altitude warning system.
- C. Differential pressure limiting is the job of the positive pressure relief (safety) valve, not the controller.
Cabin Pressurization Controller
A system that automatically schedules cabin altitude versus aircraft altitude and commands the outflow valve position to maintain that schedule.
- Follows a preset cabin altitude-vs-aircraft altitude schedule
- Signals outflow valve motor to adjust cabin pressure
- Separate from safety and negative pressure relief valves
Memory trick: The controller is the conductor, keeping the cabin's 'altitude orchestra' in schedule.