FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsHard
A technician is troubleshooting a transport-category air cycle cooling pack and notes that hot bleed air is passed through a heat exchanger, further compressed, cooled again, and then expanded through a turbine before entering the cabin. What is the primary purpose of expanding the air through this turbine?
- AIncrease air pressure for cabin pressurization
- BExtract energy from the air to produce a substantial temperature drop for cooling
- CRemove moisture from the airstream before distribution
- DRegulate cabin altitude by controlling outflow valve position
Show answer & explanationAnswer & explanation
Correct answer: B. Extract energy from the air to produce a substantial temperature drop for cooling
In an air cycle machine, expanding compressed air through the expansion turbine causes it to do work, extracting energy and dramatically lowering its temperature, which produces the cold air supplied to the cabin.
Why the other options are wrong
- A. Expansion through the turbine drops pressure, it does not increase it.
- C. Moisture removal is performed by a separate water extractor/separator downstream, not the turbine itself.
- D. Outflow valve control is a separate pressurization function unrelated to the ACM turbine.
Air Cycle Machine (ACM) Cooling Pack
A bleed-air cooling system that compresses, cools, and then expands air through a turbine to produce cold air for cabin air conditioning.
- Uses bleed air as its source
- Turbine expansion extracts energy causing a large temperature drop
- Turbine also drives the compressor and cooling fan
Memory trick: Spinning the turbine sucks the heat right out of the air, like a fan blowing away warmth.