Combustion ChambersAircraft & Engines — DGCA CPL practice questions

All 5 questions — Combustion Chambers

Aircraft & Engines · DGCA CPL. The correct option is marked on each.

1. Q1. The proportion of combustion chamber air actually burned with fuel (primary air) is about:

   • A.20%✓
   • B.40%
   • C.60%
   • D.100%

   Why: Primary ~20% burns; secondary ~20% anchors the flame; tertiary ~60% cools the flame tube and dilutes the gas for the turbine.

2. Q2. The most modern and efficient combustion chamber design is the:

   • A.Multiple can
   • B.Tubo-annular (can-annular)
   • C.Annular✓
   • D.Reverse-flow can

   Why: The single ring-shaped annular chamber gives the best combustion efficiency, temperature distribution and a shorter engine.

3. Q3. Tertiary air cools the combustion gases from a peak of roughly 2000°C to a turbine-entry temperature of:

   • A.100-300°C
   • B.500-700°C
   • C.1000-1500°C✓
   • D.1800-1900°C

   Why: The film of tertiary air protects the flame-tube walls then mixes in, bringing gas temperature down to what the turbine can survive.

4. Q4. An engine can only be relit in flight:

   • A.At any altitude and speed
   • B.Within a specific relight envelope of altitude and airspeed✓
   • C.Below 10,000 ft only
   • D.With the APU running

   Why: Outside the relight envelope the airflow may be too fast or the air too thin to support ignition.

5. Q5. Swirl vanes at the front of the flame tube serve to:

   • A.Cool the casing
   • B.Create a vortex that stabilises the flame✓
   • C.Filter the fuel
   • D.Increase exhaust velocity

   Why: The swirling primary air creates a stable, anchored flame that stays alight across the operating range.