Free UK Part-66 Module 15 Gas Turbine Engine B1.1 Practice Questions

Sample Practice Questions

Try these 10 sample questions from the UK Part-66 Module 15 Gas Turbine Engine B1.1 practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1Which thermodynamic cycle describes the ideal operation of an aircraft gas turbine?

   1. A.Otto cycle
   2. B.Brayton cycleCorrect answer: B
   3. C.Diesel cycle
   4. D.Rankine cycle

   Explanation: The FAA handbook states: "The Brayton cycle is the name given to the thermodynamic cycle of a gas turbine engine to produce thrust." It models continuous-flow gas-turbine operation rather than reciprocating combustion or steam power.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 1, p. 1-58

2. 2What is the principal aerodynamic objective of a gas-turbine inlet?

   1. A.Create maximum swirl before the compressor
   2. B.Deliver air with minimum energy loss and turbulenceCorrect answer: B
   3. C.Raise exhaust velocity before combustion
   4. D.Reduce inlet pressure to promote fuel atomisation

   Explanation: The FAA handbook states: "The air entrance is designed to conduct incoming air to the compressor with a minimum energy loss" Inlet losses reduce the useful pressure available to the compressor.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 1, p. 1-37

3. 3Why must turbine nozzle-vane mounting arrangements accommodate thermal expansion?

   1. A.To prevent distortion during temperature changesCorrect answer: A
   2. B.To eliminate the need for nozzle cooling
   3. C.To let the nozzle rotate with the turbine disc
   4. D.To increase the turbine shaft's rotational speed

   Explanation: The FAA handbook states: "the nozzle vanes must be constructed to allow thermal expansion. Otherwise, there would be severe distortion or warping" Mounting must allow expansion instead of restraining the hot vanes and causing distortion.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 1, p. 1-47

4. 4Which main-shaft bearing can carry both radial and axial thrust loads?

   1. A.A straight cylindrical roller bearing
   2. B.A plain radial sleeve without thrust faces
   3. C.A deep-groove ball bearingCorrect answer: C
   4. D.A floating labyrinth seal

   Explanation: The FAA handbook states: "one deep groove ball bearing (thrust and radial loads) and one straight roller bearing (radial load only)" The ball bearing locates the shaft axially as well as supporting radial load; the straight roller bearing permits axial freedom.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 1, p. 1-52

5. 5Where is most oil stored in a dry-sump turbine lubrication system?

   1. A.In an external oil tankCorrect answer: A
   2. B.In the individual bearing sumps
   3. C.In an integral accessory-case reservoir
   4. D.In the main rotor shaft's hollow interior

   Explanation: The FAA handbook states: "dry-sump engines utilize an external tank mounted on the engine or somewhere in the aircraft structure near the engine" The external reservoir distinguishes the dry-sump arrangement from oil storage in the engine proper.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 6, p. 6-20

6. 6Why is compressor rotation established before fuel is introduced during a turbine-engine start?

   1. A.To drain all oil from the bearing cavities
   2. B.To heat the fuel above its flash point externally
   3. C.To establish airflow capable of supporting combustionCorrect answer: C
   4. D.To prevent any pressure rise in the combustion section

   Explanation: The FAA handbook states: "there must be sufficient airflow through the engine to support combustion before the air-fuel mixture is ignited." Starting airflow is a necessary combustion condition; fuel must not precede adequate cranking airflow.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 5, p. 5-8

7. 7How can water injection restore some thrust lost on a hot day?

   1. A.By reducing inlet temperature and increasing air densityCorrect answer: A
   2. B.By raising gas temperature ahead of the first turbine
   3. C.By decreasing the density of the compressor inlet air
   4. D.By reducing mass flow while holding inlet temperature fixed

   Explanation: The FAA handbook states: "This lowers the air temperature and increases air density." Water injection counters the hot-day reduction in air density.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 2, p. 2-40

8. 8What does the freewheeling unit do if a helicopter's engine slows below the rotor drive speed?

   1. A.Locks the rotor to the stopped engine
   2. B.Disengages the engine so the rotor can continue turningCorrect answer: B
   3. C.Reverses the direction of the power turbine
   4. D.Shuts the rotor transmission oil supply

   Explanation: The FAA handbook states: "The freewheeling unit automatically disengages the engine from the main rotor when engine revolutions per minute (rpm) is less than main rotor rpm." The overrunning clutch prevents the slowing engine from dragging down the rotor.

   Reference: FAA Helicopter Flying Handbook — Chapter 4, p. 4-6

9. 9How are thermal switches connected in the fire-warning arrangement described by the FAA?

   1. A.In parallel so any heated switch can complete the warning circuitCorrect answer: A
   2. B.In series so every switch must close before warning occurs
   3. C.In parallel so the warning only works if all switches are open
   4. D.In series so a single open switch completes the warning circuit

   Explanation: The FAA handbook states: "They are connected in parallel with each other, but in series with the indicator lights" Parallel sensors permit any one closed switch to energise the common warning circuit.

   Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 9, p. 9-2

10. 10Why must the applicable preservation procedure be selected for the planned period of turbine-engine inactivity?

    1. A.Required treatment depends partly on the storage duration.Correct answer: A
    2. B.Every turbine uses one identical procedure for all storage periods.
    3. C.Oil and fuel systems always require identical preservatives.
    4. D.Engine rotation permissions are independent of preservation method.

    Explanation: The FAA handbook states: "The procedures for preserving and depreserving gas turbine engines vary depending upon the length of inactivity" Duration is one factor in selecting the treatment, along with preservative type and rotation restrictions.

    Reference: FAA Aviation Maintenance Technician Handbook—Powerplant — Chapter 8, p. 8-22