The Turbine AssemblyAircraft & Engines — DGCA CPL practice questions
Question 1 of 5
Nozzle Guide Vanes (NGVs):
All 5 questions — The Turbine Assembly
Aircraft & Engines · DGCA CPL. The correct option is marked on each.
Q1. Nozzle Guide Vanes (NGVs):
- A.Rotate with the turbine disc
- B.Form convergent ducts that accelerate and direct gas onto the turbine blades✓
- C.Cool the exhaust
- D.Reverse the thrust
Why: Stationary NGVs accelerate the hot gas and aim it at the optimum angle onto the rotating turbine blades.
Q2. The gradual stretching of turbine blades under heat and centrifugal load is called:
- A.Fatigue
- B.Creep✓
- C.Shear
- D.Flutter
Why: Creep is permanent elongation over time; blades have a finite life in operating cycles because of it.
Q3. Turbine blades are commonly attached to the disc by a:
- A.Weld
- B.Fir-tree root fixing✓
- C.Single bolt
- D.Adhesive bond
Why: The fir-tree root allows thermal expansion while holding the blade against enormous centrifugal force.
Q4. Modern turbine blades survive gas hotter than their alloy's melting point because they are:
- A.Painted with ceramic
- B.Hollow and internally cooled by compressor bleed air✓
- C.Made of titanium
- D.Spinning too fast to melt
Why: Cooler compressor air flows through intricate internal passages, keeping the blade metal below its limits.
Q5. As gas passes through a turbine stage, its pressure, temperature and velocity:
- A.All increase
- B.All decrease✓
- C.Pressure rises, temperature falls
- D.Stay constant
Why: The turbine extracts energy from the gas to drive the compressor; the gas leaves with lower pressure, temperature and velocity.