FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsMedium
A technician is troubleshooting a transport-category aircraft's cabin recirculation fan, which is inoperative. What is the primary purpose of this fan within the environmental control system?
- AIt exhausts cabin air overboard through the outflow valve
- BIt pressurizes the cabin independently of the bleed air system
- CIt supplies emergency oxygen to the passenger cabin during depressurization
- DIt draws a portion of cabin air through filters and mixes it with conditioned bleed air to reduce bleed air demand
Show answer & explanationAnswer & explanation
Correct answer: D. It draws a portion of cabin air through filters and mixes it with conditioned bleed air to reduce bleed air demand
The cabin recirculation fan pulls filtered cabin air and mixes it with fresh conditioned bleed air, reducing the amount of engine bleed air required and improving fuel efficiency while maintaining air quality.
Why the other options are wrong
- A. Exhausting cabin air is the outflow valve's function, not the recirculation fan's.
- B. Cabin pressurization is provided by bleed air and controlled by the outflow valve, not the recirculation fan.
- C. Emergency oxygen is a separate system unrelated to recirculation fans.
Cabin Air Recirculation Fan
A fan in the environmental control system that recirculates filtered cabin air, mixing it with fresh bleed air to reduce bleed air demand.
- Improves fuel efficiency by reducing bleed air extraction
- Air passes through HEPA filters before recirculation
- Works alongside the air cycle machine pack for cabin conditioning
Memory trick: Recirc fan recycles cabin air like a home HVAC return duct.