Introduction to Gas Turbine EnginesAircraft & Engines — DGCA CPL practice questions
Question 1 of 5
The gas turbine engine operates on the:
All 5 questions — Introduction to Gas Turbine Engines
Aircraft & Engines · DGCA CPL. The correct option is marked on each.
Q1. The gas turbine engine operates on the:
- A.Otto cycle (constant volume)
- B.Brayton cycle (constant pressure)✓
- C.Carnot cycle
- D.Diesel cycle
Why: Combustion in a gas turbine occurs at nearly constant pressure (Brayton cycle), continuously — unlike the piston engine's constant-volume Otto cycle.
Q2. A divergent duct in subsonic flow:
- A.Speeds the air up and raises pressure
- B.Slows the air down and raises pressure✓
- C.Slows the air down and lowers pressure
- D.Has no effect
Why: Widening duct → velocity converts to pressure; used in subsonic intakes and after the compressor. Convergent ducts do the opposite.
Q3. In a turbo-prop engine, thrust comes approximately:
- A.90% from the propeller, 10% residual jet thrust✓
- B.50% propeller, 50% jet
- C.10% propeller, 90% jet
- D.Entirely from the jet
Why: The turbine extracts most of the gas energy to drive the propeller; total output is measured in Equivalent Shaft Horsepower (ESHP).
Q4. By-pass ratio is the ratio of:
- A.Hot stream mass flow to cold stream mass flow
- B.Cold (by-pass) stream mass flow to hot (core) stream mass flow✓
- C.Fan diameter to core diameter
- D.Thrust to weight
Why: BPR = air ducted around the core ÷ air through the core. High-BPR fans (5:1+) are quieter and more fuel-efficient at subsonic speeds.
Q5. The maximum temperature in a gas turbine is limited by:
- A.The fuel's octane rating
- B.The metallurgical limits of the nozzle guide vanes and turbine blades✓
- C.The compressor RPM
- D.The intake design
Why: Hotter combustion means better efficiency, but the NGVs and turbine blades set the metallurgical ceiling.