Pneumatic Systems, Air Conditioning, and PressurizationAircraft & Engines — DGCA CPL practice questions
Question 1 of 5
The most common source of air for pneumatic services on a jet transport is:
All 5 questions — Pneumatic Systems, Air Conditioning, and Pressurization
Aircraft & Engines · DGCA CPL. The correct option is marked on each.
Q1. The most common source of air for pneumatic services on a jet transport is:
- A.Ram air
- B.Engine compressor bleed air✓
- C.An electric compressor
- D.Exhaust gas
Why: Hot high-pressure air is bled from the engine compressors, with valves selecting LP or HP stages depending on engine RPM.
Q2. In the bootstrap air-cycle system, the large temperature drop is produced by:
- A.A heat exchanger
- B.Rapid expansion of the air across a turbine✓
- C.Mixing with ram air
- D.A refrigerant gas
Why: After pre-cooling and re-compression, the air expands across a turbine and its temperature plummets — the turbine's work helps drive the compressor.
Q3. Cabin pressure is controlled primarily by:
- A.Varying pack output
- B.Modulating the outflow valve(s)✓
- C.The dump valve
- D.Engine RPM
Why: Packs supply a constant mass flow; closing the outflow valve raises cabin pressure (lowers cabin altitude), opening it does the reverse.
Q4. The inward relief valve protects the structure when:
- A.Cabin pressure exceeds outside pressure
- B.Outside pressure exceeds cabin pressure, e.g. in a rapid descent✓
- C.The packs fail
- D.On the ground only
Why: Outward relief prevents exceeding max differential; inward relief prevents outside pressure crushing inwards during rapid descent.
Q5. A typical maximum cabin altitude maintained in cruise is:
- A.Sea level
- B.8,000 ft or lower✓
- C.15,000 ft
- D.25,000 ft
Why: Pressurisation keeps the cabin at a safe, comfortable altitude (≤ ~8,000 ft) while the aircraft cruises far higher.