The Exhaust System and Thrust ReversalAircraft & Engines — DGCA CPL practice questions
Question 1 of 4
A 'choked' propelling nozzle means the exhaust gas at the nozzle exit has reached:
All 4 questions — The Exhaust System and Thrust Reversal
Aircraft & Engines · DGCA CPL. The correct option is marked on each.
Q1. A 'choked' propelling nozzle means the exhaust gas at the nozzle exit has reached:
- A.Maximum temperature
- B.The local speed of sound (Mach 1.0)✓
- C.Zero static pressure
- D.The turbine entry temperature
Why: Once choked, exit velocity can only rise by increasing gas temperature — e.g. with afterburner/reheat.
Q2. On a high by-pass turbofan, thrust reversal is achieved by:
- A.Reversing fan rotation
- B.Blocker doors redirecting the cold by-pass air forward through cascade vanes✓
- C.Clamshell doors in the hot exhaust only
- D.Variable-pitch turbine blades
Why: The cold-stream reverser blocks the fan duct and turns that air forward; the hot core flow is unaffected. Clamshell/bucket doors suit pure jets.
Q3. Thrust reversers can normally be deployed only when:
- A.Airspeed is below 80 kt
- B.Throttles are at idle and weight-on-wheels confirms the aircraft is on the ground✓
- C.The APU is running
- D.Flaps are retracted
Why: Safety interlocks require idle thrust levers plus ground (squat switch) logic before the reversers will deploy.
Q4. The exhaust cone behind the turbine serves to:
- A.Accelerate the gas to supersonic speed
- B.Smooth the gas flow and prevent turbulence✓
- C.Cool the turbine disc
- D.House the APU
Why: The cone fairs the flow off the turbine into the jet pipe; the final convergent propelling nozzle then accelerates it.