DGCA & EASA Module 15 : Part-7 Engine Exhaust Section Question
DGCA & EASA Module 15 : Part-7 Engine Exhaust Section Question-Answer
1. The function of the exhaust cone assembly of a turbine engine is to.
A. swirl and collect the exhaust gases into a single exhaust jet.
B. collect the exhaust gases and act as a noise suppressor.
C. straighten and collect the exhaust gases into a solid exhaust jet.
Ans : straighten and collect the exhaust gases into a solid exhaust jet.
Explanation: Jeppesen A&P Powerplant Textbook 3-20.
2. A nozzle is 'choked' when the gas flow or air flow at the throat is.
A. sonic.
B. subsonic.
C. supersonic.
Ans : sonic.
Explanation: Rolls Royce The Jet Engine page 14; refers.
3. The struts on the exhaust cone.
A. straighten the gas flow only.
B. support the exhaust cone and straighten the gas flow.
C. support the exhaust cone only.
Ans : support the exhaust cone and straighten the gas flow.
Explanation: NIL.
4. A nozzle is 'choked' when the engine inlet airflow is.
A. subsonic.
B. supersonic.
C. subsonic or supersonic.
Ans : subsonic or supersonic.
Explanation: NIL.
5. What is the maximum practical angle through which the gas flow can be turned during thrust reversal?.
A. 180°.
B. 50°.
C. 135°.
Ans : 135°.
Explanation: Rolls Royce The Jet Engine page 160 refers.
6. A supersonic duct is.
A. convergent then divergent along its length.
B. divergent then convergent along its length.
C. a convergent duct that is choked at the largest end at mach 1.
Ans : convergent then divergent along its length.
Explanation: Visualise the exhaust nozzle of the space shuttle booster rockets.
7. Noise from the jet wake when untreated by suppression is.
A. high frequency, high decibel.
B. low frequency, low decibel.
C. low frequency, high decibel.
Ans : low frequency, high decibel.
Explanation: Jepperson Gas Turbine Powerplants Page 3-57 refers.
8. Hot spots on the tail cone of a turbine engine are possible indicators of a malfunctioning fuel nozzle or.
A. a faulty igniter plug.
B. an improperly positioned tail cone.
C. a faulty combustion chamber.
Ans : a faulty combustion chamber.
Explanation: NIL.
9. An exhaust cone placed aft of the turbine in a jet engine will cause the pressure in the first part of the exhaust duct to.
A. increase and the velocity to decrease.
B. decrease and the velocity to increase.
C. increase and the velocity to increase.
Ans : increase and the velocity to decrease.
Explanation: Jeppesen A&P Powerplant Textbook 3-30.
10. A convergent-divergent nozzle.
A. requires the aircraft to be travelling at supersonic speeds.
B. makes maximum use of pressure thrust.
C. produces a type of thrust known as kinetic thrust.
Ans : makes maximum use of pressure thrust.
Explanation: NIL.
11. The velocity of supersonic air as it flows through a divergent nozzle.
A. decreases.
B. increases.
C. is inversely proportional to the temperature.
Ans : increases.
Explanation: NIL.
12. The Jet Pipe of a gas turbine engine.
A. protects the airframe from heat damage.
B. has an inner cone to protect the rear turbine disc.
C. is convergent in shape to increase the velocity as much as possible.
Ans : protects the airframe from heat damage.
Explanation: NIL.
13. For what purpose is the propelling nozzle of a gas turbine engine designed?.
A. To increase the velocity and decrease the pressure of the gas stream leaving the nozzle.
B. To decrease the velocity and increase the pressure of the gas stream leaving the nozzle.
C. To increase the velocity and pressure of the gas stream leaving the nozzle.
Ans : To increase the velocity and decrease the pressure of the gas stream leaving the nozzle.
Explanation: NIL.
14. If the exit area of the nozzle was too large, the effect is.
A. exit velocity lower causing loss of thrust.
B. will choke at a lower gas temperature.
C. exit velocity lower, negligible effect on thrust.
Ans : exit velocity lower causing loss of thrust.
Explanation: NIL.
15. A choked nozzle.
A. increases thrust.
B. decreases thrust.
C. has no effect on the thrust.
Ans : increases thrust.
Explanation: NIL.
16. The exhaust section is designed to.
A. increase temperature, therefore increasing velocity.
B. decrease temperature, therefore decreasing pressure.
C. impart a high exit velocity to the exhaust gases.
Ans : impart a high exit velocity to the exhaust gases.
Explanation: NIL.
17. Reverse thrust can only be selected when the throttle is.
A. closed.
B. 75% power position.
C. open.
Ans : closed.
Explanation: Rolls Royce The Jet Engine page 160 refers.
18. A Convergent-Divergent nozzle.
A. makes maximum use of Pressure thrust.
B. produces a type of thrust known as kinetic thrust.
C. requires the aircraft to be travelling at supersonic speeds.
Ans : makes maximum use of Pressure thrust.
Explanation: Jeppesen Gas Turbine Powerplants Page 3-49 refers.
19. On front fan engines, to obtain thrust reversal, the.
A. hot and cold streams are reversed.
B. hot stream is reversed.
C. cold stream is reversed.
Ans : cold stream is reversed.
Explanation: Rolls Royce The Jet Engine page 159 refers.
20. Exhaust noise can be reduced by.
A. lowering the vibration frequency.
B. increasing the mixing rate.
C. increasing the jet velocity.
Ans : increasing the mixing rate.
Explanation: Rolls Royce The Jet Engine page 201 refers.
21. Operating thrust reversers at low ground speeds can sometimes cause.
A. sand or other foreign object ingestion, hot gas re-ingestion.
B. hot gas re-ingestion, compressor stalls.
C. sand or other foreign object ingestion, hot gas re-ingestion, compressor stalls.
Ans : sand or other foreign object ingestion, hot gas re-ingestion, compressor stalls.
Explanation: Jeppesen A&P Technician Propulsion Textbook 6-10.
22. Thrust reversers utilizing a pneumatic actuating system, usually receive operating pressure from.
A. the engine bleed air system.
B. high pressure air reservoirs.
C. an on-board hydraulic or electrical powered compressor.
Ans : sand or other foreign object ingestion, hot gas re-ingestion, compressor stalls.
Explanation: NIL.
23. The purpose of cascade vanes in a thrust reversing system is to.
A. turn the exhaust gases forward just after exiting the exhaust nozzle.
B. form a solid blocking door in the jet exhaust path.
C. turn to a forward direction the fan and/or hot exhaust gases that have been blocked from exiting through the exhaust nozzle.
Ans : turn to a forward direction the fan and/or hot exhaust gases that have been blocked from exiting through the exhaust nozzle.
Explanation: NIL.
24. A convergent exhaust nozzle produces mainly.
A. momentum and pressure thrust.
B. momentum thrust.
C. pressure thrust.
Ans : momentum thrust.
Explanation: Rolls Royce The Jet Engine Page 218.
25. The rearward thrust capability of an engine with the thrust reverser system deployed is.
A. equal to or less than its forward capability, depending on ambient conditions and system design.
B. less than its forward capability.
C. equal to its forward capability.
Ans : less than its forward capability.
Explanation: Jeppesen A&P Technician Propulsion Textbook 6-10.
26. Which statement is generally true regarding thrust reverser systems?.
A. Engine thrust reversers on the same aircraft usually will not operate independently of each other (must all be simultaneously).
B. It is possible to move some aircraft backward on the ground using reverse thrust.
C. Mechanical blockage system design permits a deployment position aft of the exhaust nozzle only.
Ans : It is possible to move some aircraft backward on the ground using reverse thrust.
Explanation: Jeppesen A&P Technician Propulsion Textbook 6-9.
27. What is the proper operating sequence when using thrust reversers to slow an aircraft after landing?.
A. Advance thrust levers up to takeoff position as conditions require, select thrust reverse, deselect thrust reverser, retard thrust levers to ground idle.
B. Retard thrust levers to ground idle, raise thrust reverser levers as required, and retard thrust reverser levers to ground idle.
C. Select thrust reverse, advance thrust reverser levers no higher than 75% N1, and retard thrust reverser levers to idle at approximately normal taxi speed.
Ans : Retard thrust levers to ground idle, raise thrust reverser levers as required, and retard thrust reverser levers to ground idle.
Explanation: Jeppesen A&P Technician Propulsion Textbook 6-9.
28. Most exhaust system failures result from thermal fatigue cracking in the areas of stress concentration. This condition is usually caused by.
A. the high temperatures at which the exhaust system operates.
B. improper welding techniques during manufacture.
C. the drastic temperature change which is encountered at altitude.
Ans : the high temperatures at which the exhaust system operates.
Explanation: NIL.
29. Thrust reversal on a high bypass engine is achieved by.
A. blocker doors.
B. clamshell configuration.
C. bucket type doors.
Ans : blocker doors.
Explanation: RR Page 160 figure.15-2 refers but see also Jeppesen Aircraft Gas Turbine Powerplant Page 3-50.
30. If damage is found to the reverse thrust cascade vanes and they need replacing, you can.
A. replace damaged vanes with 45 degree vanes.
B. only replace vanes with new ones that have the correct part as the originals removed.
C. interchange the cascade vanes as they are interchangeable.
Ans : only replace vanes with new ones that have the correct part as the originals removed.
Explanation: Cascade vane segments are NOT interchangeable, they all direct air at different angles.
31. When should thrust reversers be used?.
A. At low RPM and low forward speed.
B. At high RPM and high forward speed.
C. At high RPM and low forward speed.
Ans : At low RPM and low forward speed.
Explanation: Thrust reversers cannot be actuated if the throttles are set above idle and they can only be used on the ground.
32. If the area of the nozzle was too large the effect is.
A. will 'choke' at mach 1.
B. exit velocity lower causing loss of the thrust.
C. exit velocity lower, negligible effect on thrust.
Ans : exit velocity lower causing loss of the thrust.
Explanation: Jeppesen Aircraft Gas Turbine Powerplant page 2-20 and others.
33. Lobe type exhaust noise suppressors are made from.
A. heat resistant alloy.
B. composite Material.
C. steel.
Ans : heat resistant alloy.
Explanation: Rolls Royce The Jet Engine Page 205 refers.
34. What indication does the pilot receive that thrust reversers have deployed?.
A. An audible warning.
B. A sequence of lights.
C. A feeling of rapid deceleration.
Ans : A sequence of lights.
Explanation: Boeing 757/767 use the word 'rev' in amber for unlocked and green for deployed on the upper EICAS screen.
35. What angle are the exhaust gasses turned through in a clamshell type thrust reverser?.
A. 180 degrees.
B. 135 degrees.
C. 45 degrees.
Ans : 135 degrees.
Explanation: Turned through 135 degrees is 45 degrees forward, the maximum a thrust reverser of any sort turns the air forward.
36. The purpose of a propelling nozzle is to.
A. increase the velocity of the air and increase thrust.
B. decrease the velocity of the exhaust to increase static pressure.
C. direct the air onto the turbines.
Ans : increase the velocity of the air and increase thrust.
Explanation: The convergence of the propelling nozzle in a subsonic pure jet engine is set so that max speed is just below Mach 1.
37. If a thrust reverser is deployed at lower than normal landing speed.
A. exhaust gases can be ingested into the engine.
B. the thrust reverser will be ineffective.
C. if the EGT gets too high the thrust reverser will automatically restow.
Ans : exhaust gases can be ingested into the engine.
Explanation: Exhaust gas ingestion is a problem for thrust reverser systems when stationary or very slow.
38. The size of the exhaust section is dictated by.
A. cone or diffuser size and location.
B. size of engine only.
C. size and location of the engine.
Ans : size and location of the engine.
Explanation: The exhaust section is of a certain diameter and can be of different lengths depending on the location of the engine within the fuselage or wing root (IE English Electric Lightning).
39. On a Clamshell door type thrust reverser. The Clamshell doors redirect the exhaust gas stream.
A. 0 degrees to the thrust line.
B. 45 degrees to the thrust line.
C. 90 degrees to the thrust line.
Ans : 45 degrees to the thrust line.
Explanation: 45 degrees to the thrust line is an alternative to 'turned through 135 degrees'.
40. Normal gas turbine engine's exhaust duct is.
A. divergent.
B. convergent/divergent.
C. convergent.
Ans : convergent.
Explanation: The exhaust nozzle consists of a parallel duct then the propelling nozzle which is always convergent.
41. As the air flows out at the outflow of a choked nozzle.
A. velocity increases and pressure decreases.
B. velocity and pressure decrease.
C. velocity decreases and pressure increases.
Ans : velocity decreases and pressure increases.
Explanation: A choked nozzle has a shock wave in it and air is at Mach 1. After the shock the air must be decreased in speed and pressure is rising.Click Here For : DGCA & EASA Module 15 : Part-8 Engine's Bearings and Seals Question
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