15.4 Engine Compressors.

1. A bypass engine LP compressor.

A. supplies less air than is required for combustion.

B. supplies more air than is required for combustion.

C. supplies only the required quantity for combustion.

Ans.- supplies more air than is required for combustion.

Explanation. By definition the bypass duct sends air around the combustion chamber.

2. How does a dual axial flow compressor improve the efficiency of a turbojet engine?.

A. The velocity of the air entering the combustion chamber is increased.

B. More turbine wheels can be used.

C. Higher compression ratios can be obtained.

Ans.- Higher compression ratios can be obtained.

Explanation. Jeppesen A&P Powerplant Textbook 3-13.

3. In a reverse flow system, the last stage of an axial flow compressor is often centrifugal. This is to.

A. provide initial turning of the airflow.

B. prevent compressor surge.

C. increase the temperature rise.

Ans.- provide initial turning of the airflow.

Explanation. Rolls Royce The Jet engine Page 5 refers.

4. What are the two main functional components in a centrifugal compressor?.

A. Bucket and expander.

B. Impeller and diffuser.

C. Turbine and compressor.

Ans.- Impeller and diffuser.

Explanation. Jeppesen A&P Powerplant Textbook 3-13.

5. A bypass ratio of 5:1 indicates that the bypass flow is.

A. equal to 1/5 of the hot stream.

B. five times the hot stream.

C. five times the cold stream.

Ans.- five times the hot stream.

Explanation. Rolls Royce The Jet Engine page 16/17 refers.

6. The stator vanes in an axial-flow compressor.

A. direct air into the first stage rotor vanes at the proper angle.

B. convert velocity energy into pressure energy.

C. convert pressure energy onto velocity energy.

Ans.- convert velocity energy into pressure energy.

Explanation. Rolls Royce The Jet Engine page 25 refers.

7. What units in a gas turbine engine aid in stabilisation of the compressor during low thrust engine operations?.

A. Bleed air valves.

B. Stator vanes.

C. Inlet guide vanes.

Ans.- Bleed air valves.

Explanation. Rolls Royce The Jet Engine page 31 refers.

8. What purpose do the diffuser vanes of a centrifugal compressor serve?.

A. To convert pressure energy into kinetic energy.

B. To increase the air velocity.

C. To convert kinetic energy into pressure energy.

Ans.- To convert kinetic energy into pressure energy.

Explanation. NIL.

9. During the high RPM range on an axial flow gas turbine engine, in what position are the variable intake guide vanes and bleed valves?.

A. At maximum swirl position, bleed valves open.

B. At minimum swirl position, bleed valves closed.

C. At maximum swirl position, bleed valves closed.

Ans.- At minimum swirl position, bleed valves closed.

Explanation. Rolls Royce The Jet Engine page 29-31 refers.

10. What is the purpose of the diffuser section in a turbine engine?.

A. To convert pressure to velocity.

B. To reduce pressure and increase velocity.

C. To increase pressure and reduce velocity.

Ans.- To increase pressure and reduce velocity.

Explanation. Jeppesen A&P Powerplant Textbook 3-20.

11. The fan speed of a twin spool axial compressor engine is the same as the.

A. low pressure compressor.

B. forward turbine wheel.

C. high pressure compressor.

Ans.- low pressure compressor.

Explanation. Jeppesen A&P Powerplant Textbook 3-18.

12. Bleed valves are normally spring loaded to the.

A. closed position.

B. open position.

C. mid-position.

Ans.- open position.

Explanation. Rolls Royce The Jet Engine Page 31 refers.

13. What is the function of the stator vane assembly at the discharge end of a typical axial flow compressor?.

A. To increase air swirling motion into the combustion chambers.

B. To direct the flow of gases into the combustion chambers.

C. To straighten airflow to eliminate turbulence.

Ans.- To straighten airflow to eliminate turbulence.

Explanation. Jeppesen A&P Powerplant Textbook 3-17.

14. In a turbine engine with a dual spool compressor, the low speed compressor.

A. always turns at the same speed as the high speed compressor.

B. seeks its own best operating speed.

C. is connected directly to the high speed compressor.

Ans.- seeks its own best operating speed.

Explanation. NIL.

15. What units in a gas turbine engine aid in guiding the airflow during low thrust engine operations?.

A. Stator vanes.

B. Bleed air valves.

C. Inlet guide vanes.

Ans.- Inlet guide vanes.

Explanation. NIL.

16. What is one purpose of the stator blades in the compressor section?.

A. Increase the velocity of the airflow.

B. Stabilize the pressure of the airflow.

C. Control the direction of the airflow.

Ans.- Control the direction of the airflow.

Explanation. Jeppesen A&P Powerplant Textbook 3-17.

17. Compressor stall is caused by.

A. a low angle of attack airflow through the first stages of compression.

B. rapid engine deceleration.

C. a high angle of attack airflow through the first stages of compression.

Ans.- a high angle of attack airflow through the first

stages of compression.

Explanation. NIL.

18. What is used to aid in stabilization of compressor airflow?.

A. Variable guide vanes and/or compressor bleed valves.

B. Pressurization and dump valves.

C. Stator vanes and rotor vanes.

Ans.- Variable guide vanes and/or compressor bleed

valves.

Explanation. NIL.

19. What is the primary factor which controls the pressure ratio of an axial flow compressor?.

A. Compressor inlet temperature.

B. Compressor inlet pressure.

C. Number of stages in compressor.

Ans.- Number of stages in compressor.

Explanation. NIL.

20. The non-rotating axial-flow compressor airfoils in an aircraft gas turbine are known as.

A. stator vanes.

B. bleed vanes.

C. pressurization vanes.

Ans.- stator vanes.

Explanation. NIL.

21. The purpose of a bleed valve, located in the beginning stages of the compressor is to.

A. vent some of the air overboard to prevent a compressor stall.

B. control excessively high RPM to prevent a compressor stall.

C. vent high ram air pressure overboard to prevent a compressor stall.

Ans.- vent some of the air overboard to prevent a compressor stall.

Explanation. NIL.

22. During the low RPM range on an axial flow gas turbine engine, in what position are the variable intake guide vanes and bleed valves?.

A. At maximum swirl position, bleed valves open.

B. At maximum swirl position, bleed valves closed.

C. At minimum swirl position, bleed valves closed.

Ans.- At maximum swirl position, bleed valves open.

Explanation. NIL.

23. The energy changes that take place in the impeller of a centrifugal compressor are.

A. pressure decrease, velocity decrease, temperature increase.

B. pressure increase, velocity decrease, temperature increase.

C. pressure increase, velocity increase, temperature increase.

Ans.- pressure increase, velocity increase, temperature increase.

Explanation. rolls royce book page 21.

24. What is the primary advantage of an axial flow compressor over a centrifugal compressor?.

A. High frontal area.

B. Greater pressure ratio.

C. Less expensive.

Ans.- Greater pressure ratio.

Explanation. NIL.

25. Compression occurs.

A. across stators and rotors.

B. across rotors.

C. across stators.

Ans.- across stators and rotors.

Explanation. Jepperson Gas Turbine Powerplants

Page 3-24 refers.

26. Which of the following can cause fan blade shingling in a turbofan engine?.

A. Large, rapid throttle movements and FOD.

B. Engine over temperature, large, rapid throttle movements and FOD.

C. Engine overspeed and large, rapid throttle movements.

Ans.- Large, rapid throttle movements and FOD.

Explanation. NIL.

27. Severe rubbing of turbine engine compressor blades will usually cause.

A. cracking.

B. bowing.

C. galling.

Ans.- galling.

Explanation. Jeppesen A&P Powerplant Textbook 4-25.

28. Which two elements make up the axial flow compressor assembly?.

A. Rotor and stator.

B. Stator and diffuser.

C. Compressor and manifold.

Ans.- Rotor and stator.

Explanation. NIL.

29. If the RPM of an axial flow compressor remains constant, the angle of attack of the rotor blades can be changed by.

A. changing the compressor diameter.

B. changing the velocity of the airflow.

C. increasing the pressure ratio.

Ans.- changing the velocity of the airflow.

Explanation. NIL.

30. The gas turbine Compressor Pressure Ratio is.

A. Compressor inlet pressure divided by Compressor discharge pressure.

B. Mass of air bypassing the combustion system divided

by Mass of air going through the combustion system.

C. Compressor discharge pressure divided by Compressor inlet pressure.

Ans.- Compressor discharge pressure divided by

Compressor inlet pressure.

Explanation. NIL.

31. An advantage of the centrifugal flow compressor is its high.

A. ram efficiency.

B. pressure rise per stage.

C. peak efficiency.

Ans.- peak efficiency.

Explanation. NIL.

32. The compression ratio of an axial flow compressor is a function of the.

A. number of compressor stages.

B. air inlet velocity.

C. rotor diameter.

Ans.- number of compressor stages.

Explanation. NIL.

33. Jet engine turbine blades removed for detailed inspection must be reinstalled in.

A. the same slot.

B. a specified slot 180°away.

C. a specified slot 90°away in the direction of rotation.

Ans.- the same slot.

Explanation. Jeppesen A&P Powerplant Textbook 4-25.

34. The procedure for removing the accumulation of dirt deposits on compressor blades is called.

A. the purging process.

B. the soak method.

C. field cleaning.

Ans.- field cleaning.

Explanation. NIL.

35. The two types of centrifugal compressor impellers are.

A. impeller and diffuser.

B. single entry and double entry.

C. rotor and stator.

Ans.- single entry and double entry.

Explanation. NIL.

36. Between each row of rotating blades in a compressor, there is a row of stationary blades which act to diffuse the air. These stationary blades are called.

A. stators.

B. rotors.

C. buckets.

Ans.- stators.

Explanation. NIL.

37. Bleed valves are.

A. closed at low RPM.

B. always slightly open.

C. closed at high RPM.

Ans.- closed at high RPM.

Explanation. Jeppesen Gas Turbine Powerplants Page 8-7 Refers.

38. Compressor field cleaning on turbine engines is performed primarily in order to.

A. prevent engine oil contamination and subsequent engine bearing wear or damage.

B. prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas path surfaces.

C. facilitate flight line inspection of engine inlet and compressor areas for defects or FOD.

Ans.- prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas path surfaces.

Explanation. NIL.

39. If the LP compressor shaft severed.

A. the LP turbine will speed up and the LP compressor will slow down.

B. the LP compressor of cruise thrust.

C. the HP compressor will slow down.

Ans.- the LP turbine will speed up and the LP compressor will slow down.

Explanation. The LP Turbine is attached to the LP compressor.

40. An advantage of a centrifugal compressor is.

A. it is dynamically balanced.

B. it is unaffected by turbulence.

C. it is robust and can stand some shock from icing-up.

Ans.- it is robust and can stand some shock from icing- up.

Explanation. Rolls Royce The Jet Engine Page 19 Refers.

41. Variable inlet guide vanes prevent.

A. compressor runaway.

B. engine flame out at high speed.

C. compressor stalling.

Ans.- compressor stalling.

Explanation. Jeppesen Gas Turbine Powerplant Page 8-1 Refers.

42. An axial flow compressor surges when.

A. later stages are stalled.

B. all stages are stalled.

C. early stages are stalled.

Ans.- all stages are stalled.

Explanation. The definition of a surge is when all stages are stalled and flow reversal occurs.

43. As a consequence of tapping air from the compressor, the TGT will.

A. fall.

B. remain constant.

C. rise.

Ans.- rise.

Explanation. When a bleed valve opens it is always accompanied by a rise in TGT of 15-30 degrees.

44. Compressor air bleeds promote the flow of air through the early stages by.

A. opening to allow air in.

B. closing.

C. opening to allow air out.

Ans.- opening to allow air out.

Explanation. Jeppesen Gas Turbine Powerplant Page 8-7 refers.

45. .Compressor blades have a reduced angle of attack at the tips.

A. to prevent turbine stall.

B. to increase the velocity.

C. to allow uniform axial velocity.

Ans.- to allow uniform axial velocity.

Explanation. Jeppesen Gas Turbine Powerplant Page 3-16 refers.

46. Compressor surge is caused by.

A. over fuelling.

B. rapid closing of the throttle.

C. prolonged engine running at high RPM.

Ans.- over fuelling.

Explanation. Jeppesen Gas Turbine Powerplant Page 3-26 refers to fuel system malfunction - over fuelling.

47. Pressure rise across a single spool axial flow compressor is in the order of.

A. four to one.

B. two to one.

C. up to fifteen to one.

Ans.- up to fifteen to one.

Explanation. Rolls Royce The Jet Engine page 15 refers.

48. What purpose do the diffuser vanes of a centrifugal compressor serve?.

A. To convert pressure energy into kinetic energy.

B. To increase the air velocity.

C. To convert kinetic energy into pressure energy.

Ans.- To convert kinetic energy into pressure energy.

Explanation. NIL.

49. The purpose of the rotating guide vanes on a centrifugal compressor is to.

A. direct the air smoothly into the impeller.

B. provide initial diffusing of the air.

C. prevent damage by solid objects.

Ans.- provide initial diffusing of the air.

Explanation. Rolls Royce The Jet Engine page 21

refers.

50. What is the surge margin of an axial flow compressor?.

A. The margin between the compressor working line and the surge line.

B. The margin between minimum and maximum pressure ratio obtained at constant RPM.

C. The margin between the stall condition and the surge condition.

Ans.- The margin between the compressor working line and the surge line.

Explanation. Rolls Royce The Jet Engine figure 3-14 refers. (See the 'safety margin').

51. The compression ratio of a jet engine is.

A. the compressor outlet pressure divided by the number of compressor stages.

B. the ratio between turbine pressure and compressor outlet pressure.

C. the ratio between compressor outlet pressure and compressor inlet pressure.

Ans.- the ratio between compressor outlet pressure and

compressor inlet pressure.

Explanation. The higher the ratio the more efficient

the engine.

52. Variable inlet guide vanes help to prevent.

A. compressor runaway.

B. ice build up on compressor blades.

C. compressor stalling.

Ans.- compressor stalling.

Explanation. Rolls Royce The Jet Engine page 28 refers.

53. Air through the compressor, before entering the combustion chamber, passes.

A. through divergent passage to increase the pressure.

B. through nozzles to increase the velocity.

C. through divergent passage to decrease the pressure.

Ans.- through divergent passage to increase the pressure.

Explanation. All compressor blades and stators are divergent, and all increase pressure.

54. Low mass airflow through a compressor will produce.

A. stalling of rear stages.

B. stalling of early stages.

C. no effect.

Ans.- stalling of early stages.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplant Page 3-25 refers.

55. A bleed valve.

A. relieves compressor choking at low RPM.

B. controls air intake pressure.

C. bleeds air from compressor for intake deicing.

Ans.- relieves compressor choking at low RPM.

Explanation. Rolls Royce The Jet Engine Page 29 refers.

56. If a compressor has a compression ratio of 9:1 and an intake compression of 2:1, what is the overall compression ratio?.

A. 9:1 intake compression does not add to the overall compression ratio of the system.

B. 18:1.

C. 11:1.

Ans.- 18:1.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplant Page 3-20 refers.

57. A compressor stage stalls when.

A. adiabatic temperature rise is too high.

B. compression ratio is too high.

C. smooth airflow is disrupted.

Ans.- smooth airflow is disrupted.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplant Page 3-25 refers.

58. Inlet guide vanes are fitted to.

A. control the quantity of air entering the intake.

B. guide the airflow onto the turbine rotor first stage.

C. control the angle of airflow into the compressor.

Ans.- control the angle of airflow into the compressor.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplant Page 3-24 refers.

59. Why, in an axial flow compressor is the cross sectional area of the compressor air duct reduced at each stage?.

A. To decrease the velocity of the air rising under pressure.

B. To maintain the velocity of the air under rising pressure.

C. To permit stronger, shorter blades to be used in the later stages.

Ans.- To maintain the velocity of the air under rising pressure.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplant Page 3-24 refers.

60. An abradable lining around the fan is to.

A. provide less leakage for anti-icing.

B. prevent fan blade tip rub.

C. strengthen the EPR value.

Ans.- strengthen the EPR value.

Explanation. Prevents fan blade tip losses.

61. Allowable damage on the first stage compressor blade is restricted to.

A. middle third of the blade to the outer edge.

B. outer third of the blade to the outer edge.

C. root end of the blade.

Ans.- middle third of the blade to the outer edge.

Explanation. Jeppesen Gas Turbine Powerplants Page 5-20 refers.

62. Tip speed of a centrifugal compressor can reach.

A. Mach 1.3.

B. Mach 1.0.

C. Mach 0.8.

Ans.- Mach 1.3.

Explanation. Jeppesen Aircraft Gas turbine

Powerplant Page 3-11.

63. What is the profile of a compressor blade?.

A. A cutout that reduces blade tip thickness.

B. The leading edge of the blade.

C. The curvature of the blade root.

Ans.- A cutout that reduces blade tip thickness.

Explanation. Jeppesen A&P Technician Propulsion Textbook 3-16.

64. The resultant velocity of air exiting an axial compressor stage depends upon.

A. aircraft forward speed.

B. compressor RPM.

C. Both of the above.

Ans.- Both of the above.

Explanation. Jeppesen Aircraft Powerplant Page 3-23 Refers.

65. What is a compressor stage?.

A. One compressor rotor and one nozzle guide vane.

B. One rotor plus one stator.

C. One Nozzle Guide Vane and one rotor.

Ans.- One rotor plus one stator.

Explanation. Rolls Royce The Jet Engine Page 25 refers.

66. If the bypass ratio is 0.7:1, the 0.7 pounds of air is.

A. fed into H.P compressor compared to 1 pound fed around it.

B. fed around the engine to 1 pound fed into H.P. compressor.

C. bypassed for every 1 pound at the intake.

Ans.- fed around the engine to 1 pound fed into H.P. compressor.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplant Page 2-9 refers.

67. Advantage of an axial flow over a centrifugal flow gas turbine engine.

A. power required for starting is less.

B. low weight.

C. high peak efficiencies.

Ans.- high peak efficiencies.

Explanation. Rolls Royce The Jet engine page 21 shows how higher compression ratios (axial flow compressors) give lower SFC. Which means higher efficiency.

68. Compressor blades reduce in length.

A. from tip to root to maintain uniform velocity in compressor.

B. from L.P to H.P section to maintain uniform velocity in compressor.

C. from root to tip to maintain correct angle of attack.

Ans.- from L.P to H.P section to maintain uniform velocity in compressor.

Explanation. Rolls Royce The Jet Engine Page 22 refers.

69. Deposit build-up on compressor blades.

A. airflow is too fast for deposits to build up.

B. will not decrease efficiency but may cause corrosion.

C. can decrease compressor efficiency and cause corrosion.

Ans.- can decrease compressor efficiency and cause corrosion.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplant page 5-4 refers.

70. The diffuser after the compressor, before the combustion chamber.

A. increases velocity, decreases pressure.

B. decreases velocity, pressure increases.

C. increases velocity, pressure remains constant.

Ans.- decreases velocity, pressure increases.

Explanation. Assuming this refers to a centrifugal compressor see figure 3-6 Rolls Royce The Jet Engine.

71. In a compressor, diffusion action takes place across.

A. rotors.

B. rotors and stators.

C. stators.

Ans.- rotors and stators.

Explanation. Stators and rotors in compressors both form divergent ducts hence they both diffuse.

72. The ring of fixed blades at the intake of an axial flow compressor are called.

A. inlet guide vanes.

B. first stage stator blades.

C. first stage diffuser blades.

Ans.- inlet guide vanes.

Explanation. The fixed IGV's precede the 1st stage rotor which is in front of the 1st stage stator.

73. What is the purpose of pressure balance seal?.

A. To ensure the location bearing is adequately loaded throughout the engine thrust range.

B. To ensure LP compressor is statically balanced.

C. To ensure HP compressor is dynamically balanced.

Ans.- To ensure the location bearing is adequately loaded throughout the engine thrust range.

Explanation. Pressure balance seals oppose the tendency of compressors to move forward.

74. The optimum air speed for entrance into the compressor is approximately.

A. same as aircraft speed.

B. Mach 0.4.

C. Mach 1.

Ans.- Mach 0.4.

Explanation. Diffusion in the intake reduces the speed to 500ft/second (about mach 0.4).

75. What is the acceptable damage on stator blades that have been blended?.

A. One third along from root to tip.

B. One third from tip to root.

C. One third chord wise.

Ans.- One third from tip to root.

Explanation. The root of the blade has tighter tolerance than the tip, and chord wise indentations are also critical so our best guess is from tip to root

76. With regard to compressor blades, which of the following is true? No damage is permissible on.

A. a shroud fillet area.

B. the lip of a blade.

C. the last third of the outboard leading edge.

Ans.- a shroud fillet area.

Explanation. Shroud fillets are critical areas whereas the outer third of the blade is less so. Unshrouded tips are also less critical than shroud fillets.

77. Identify a function of the cascade vanes in a turbojet engine compressor section.

A. To remove air swirl before the combustion chamber.

B. To direct the flow of air to strike the turbine blades at

a desired angle.

C. To decrease the velocity of air to the combustor.

Ans.- To remove air swirl before the combustion chamber.

Explanation. Jeppesen Aircraft Gas Turbine

Powerplants page 3-23 describe the axial flow compressor as 'containing sets of airfoils in cascade'. It further says that the last stage of stationary vanes, called exit guide vanes turn the airflow back to an axial direction on its way to the combustor.

78. The pressure ratio can be influenced by.

A. compressor inlet temperature.

B. number of stages in compressor.

C. compressor inlet pressure.

Ans.- number of stages in compressor.

Explanation. Compressors are rated by their pressure ratio, the more stages the greater the pressure ratio.

79. Air bleed valves are.

A. closed at low RPM.

B. open at high RPM.

C. open at low RPM.

Ans.- open at low RPM.

Explanation. Air bleed valves reduce the pressure developed in a compressor until the speed is increased towards the blade design speed.

80. The compressor case annulus is.

A. convergent.

B. divergent.

C. parallel.

Ans.- convergent.

Explanation. All axial flow compressor case annulus are convergent to maintain a constant axial velocity through the compressor.

81. If the tip clearance in a centrifugal compressor is too small.

A. there would be pressure losses through leakage.

B. there is danger of seizure.

C. aerodynamic buffeting would cause vibration.

Ans.- aerodynamic buffeting would cause vibration.

Explanation. Rolls Royce The Jet Engine page 22 para 12 refers to too small a clearance setting up aerodynamic buffet.

82. A 1st stage LP compressor blade is able to continue in service if the damage is within limits, and within the.

A. middle third of blade chord-wise.

B. outer third only.

C. root section only.

Ans.- outer third only.

Explanation. Repairs across the chord or at the root are normally prohibited, outer third is the only safe answer.

83. What is meant by a compressor stage?.

A. One rotor and one stator assembly.

B. All rotors and stators.

C. One rotor and one guide vane assembly.

Ans.- One rotor and one stator assembly.

Explanation. Para 13 page 22 of Rolls Royce the Jet Engine refers.

84. What is the normal pressure rise across each compressor stage of an axial flow compressor?.

A. 1.5:1.

B. 1.2:1.

C. 5:1.

Ans.- 1.2:1.

Explanation. Para 20 page 25 of Rolls Royce the Jet Engine refers.

85. Where does compression take place as air passes through an axial flow compressor?.

A. Rotor blades.

B. Stator Blades.

C. Rotor and Stator blades.

Ans.- Rotor and Stator blades.

Explanation. Compression occurs through all stages figure 3.9 page 25 of Rolls Royce the Jet Engine refers.

86. Nozzle Guide Vane bow is an indication of.

A. engine overspeed.

B. engine overheat.

C. engine shock loading.

Ans.- engine overheat.

Explanation. Early turbines, both blades and NGV were susceptible to 'creep' -- prolonged exposure to excessive heat.

87. A build up of foreign objects and dirt on compressor blades.

A. has a large effect on compressor efficiency and may cause corrosion.

B. has no effect on the efficiency of the compressor but may cause corrosion.

C. has no effect on compressor efficiency due to the speed of rotation.

Ans.- has a large effect on compressor efficiency and may cause corrosion.

Explanation. Compressor washes are used to reduce this problem.

88. What is the purpose of the stator vanes in the compressor section of a gas turbine engine?.

A. Increase the velocity of the airflow.

B. Control direction of the airflow.

C. Prevent compressor surge.

Ans.- Control direction of the airflow.

Explanation. Rolls Royce The Jet Engine page 22 para 13.

89. In a twin spool compressor, the LP section runs at.

A. a lower RPM than the HP spool.

B. a higher RPM than the HP spool.

C. the same RPM than the HP spool.

Ans.- a lower RPM than the HP spool.

Explanation. NIL.