Module 14 Propulsion 100 Important Sentences for Revision

 1. Introduction to Propulsion

1. Propulsion provides the force to move an aircraft forward.
2. Thrust is the forward force produced by an engine.
3. Jet engines accelerate air to generate thrust.
4. Piston engines produce power through combustion of fuel and air.
5. Turbine engines are used on most modern aircraft.
6. Newton’s third law explains jet propulsion: action and reaction.
7. Propulsive efficiency measures how effectively thrust is used.
8. Specific fuel consumption shows fuel used per thrust output.
9. Turbofan engines have higher efficiency than turbojets.
10. Propeller engines are more efficient at low speeds.

2. Gas Turbine Engine Principles

11. A gas turbine engine works on the Brayton cycle.
12. The main sections are intake, compressor, combustion, turbine, and exhaust.
13. Air enters the intake with minimal pressure loss.
14. The compressor increases the air pressure.
15. Combustion adds heat energy to the compressed air.
16. The turbine extracts power from hot gases.
17. The exhaust accelerates gases to produce thrust.
18. The compressor and turbine are connected by a shaft.
19. Airflow must be smooth and continuous for stable operation.
20. Engine efficiency depends on pressure ratio and temperature.

3. Engine Types

21. A turbojet produces thrust only from exhaust gases.
22. A turbofan uses a fan to move extra air for more thrust.
23. A turboprop drives a propeller through a reduction gearbox.
24. A turboshaft powers helicopters and auxiliary equipment.
25. A ramjet has no moving parts and works at high speeds.
26. A pulsejet uses intermittent combustion for thrust.
27. A rocket carries both fuel and oxidizer.
28. Bypass ratio is the ratio of fan air to core air in a turbofan.
29. High-bypass engines are quieter and more efficient.
30. Low-bypass engines are used on faster aircraft.

4. Compressors

31. Compressors increase air pressure before combustion.
32. There are two main types: axial and centrifugal.
33. Axial compressors use rotating and stationary blades.
34. Centrifugal compressors use impellers and diffusers.
35. Multi-stage compressors achieve higher pressure ratios.
36. Bleed air is taken from compressor stages for aircraft systems.
37. Surge is an unstable airflow condition in compressors.
38. Stall occurs when air separates from compressor blades.
39. Variable stator vanes help control airflow and prevent surge.
40. Inter-stage bleed valves stabilize compressor operation.

5. Combustion Section

41. The combustion chamber burns fuel with compressed air.
42. The three types are can, annular, and can-annular.
43. Fuel injectors spray fuel into the airflow.
44. Igniters provide spark during engine start.
45. Continuous combustion ensures constant thrust.
46. Air cools the liner to prevent overheating.
47. Combustion efficiency affects engine performance.
48. Uneven burning can cause vibration and damage.
49. Flameout is loss of combustion during operation.
50. Relight systems restart combustion after flameout.

6. Turbine Section

51. Turbines extract energy to drive the compressor and accessories.
52. A turbine consists of rotors and stators.
53. High-pressure turbine drives the compressor.
54. Low-pressure turbine drives the fan or propeller.
55. Turbine blades are made from high-temperature alloys.
56. Cooling air flows through blade holes to reduce heat.
57. Shrouds prevent gas leakage around blades.
58. Blade creep occurs due to prolonged high temperature.
59. Over-temperature can cause turbine failure.
60. Turbine efficiency determines overall engine performance.

7. Exhaust and Thrust Reversers

61. The exhaust nozzle accelerates gases to produce thrust.
62. Convergent nozzles are used in subsonic engines.
63. Convergent-divergent nozzles are used in supersonic engines.
64. Afterburners increase thrust by burning extra fuel in exhaust.
65. Thrust reversers help slow the aircraft after landing.
66. Bucket, cascade, and clamshell are types of reversers.
67. Thrust reversers operate hydraulically or pneumatically.
68. Deploying reversers in flight is prohibited.
69. Nozzle area affects exhaust velocity and efficiency.
70. Exhaust temperature is monitored for engine health.

8. Engine Starting and Ignition

71. Engine starting turns the compressor to begin airflow.
72. Air turbine starters use compressed air to spin the engine.
73. Electrical starters are common on small engines.
74. Ignition systems provide spark for fuel ignition.
75. There are two igniters for reliability.
76. Ignition is used only during start and relight.
77. High-energy igniters produce strong sparks.
78. Dual ignition improves reliability and redundancy.
79. Ignition exciters store energy for discharge.
80. Starter cutout occurs when the engine is self-sustaining.

9. Engine Control and Monitoring

81. FADEC means Full Authority Digital Engine Control.
82. FADEC controls fuel flow and engine parameters automatically.
83. It eliminates mechanical linkages in control systems.
84. EPR (Engine Pressure Ratio) measures engine thrust.
85. N1 and N2 represent rotational speeds of compressor spools.
86. EGT (Exhaust Gas Temperature) indicates turbine temperature.
87. Oil pressure and temperature are continuously monitored.
88. Vibration sensors detect unbalance or bearing wear.
89. Engine indicating systems use digital displays in modern aircraft.
90. Over-speed protection prevents engine damage.

10. Fuel, Oil, and Fire Systems

91. The fuel system delivers fuel from tanks to the combustion chamber.
92. Fuel pumps supply pressurized fuel to the injectors.
93. Filters remove contamination from the fuel.
94. Fuel control units meter correct fuel flow.
95. Oil systems lubricate and cool engine components.
96. Scavenge pumps return oil to the tank.
97. Chip detectors indicate metal particles in oil.
98. Fire detection systems use loops or sensors.
99. Fire extinguishing systems use halon or clean agent bottles.
100. Regular inspection ensures reliable engine operation and safety.

 

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Module 14 Propulsion Final Practice Exam (24 Questions 30 Mints)

Module - 14 (Propulsion)

Final Practice Exam Test

  

 

1. What is the primary cause of engine vibrations?
   1.   Excessive fuel flow
   2.   Uneven airflow through the engine
   3.   Imbalance in the engine's rotating components
2. How does the engine’s variable nozzle assist in managing performance?
   1.   By increasing the engine’s thrust output
   2.   By adjusting the exhaust gas flow for optimal engine efficiency
   3.   By controlling the temperature of the exhaust gases
3. What happens when a jet engine experiences a flameout?
   1.   The engine’s fuel supply is interrupted, causing the engine to stop producing thrust
   2.   The engine overheats, causing the turbine to fail
   3.   The engine produces excessive thrust
4. What is the main purpose of a centrifugal compressor in a jet engine?
   1.   To increase the temperature of the incoming air
   2.   To increase the pressure of the incoming air before it enters the combustion chamber
   3.   To reduce the speed of the exhaust gases
5. What is a characteristic of a high bypass ratio turbofan engine?
   1.   It is more suitable for supersonic flight
   2.   It produces more noise than a low bypass ratio turbofan
   3.   A larger proportion of air bypasses the engine core for increased efficiency
6. What is the role of the engine’s oil filter?
   1.   To assist in combustion
   2.   To monitor fuel pressure
   3.   To prevent contamination in the engine oil
7. What is the primary advantage of using a turbofan engine over a turbojet engine?
   1.   Higher speed
   2.   Greater fuel efficiency
   3.   Smaller size
8. What is the purpose of the variable stator blades in a jet engine?
   1.   To increase the airflow into the engine
   2.   To reduce the temperature of the exhaust gases
   3.   To control the airflow to the turbine
9. What is the function of the engine’s thrust rating system?
   1.   To provide thrust limits based on engine conditions
   2.   To monitor fuel consumption during flight
   3.   To control the speed of the propeller
10. What type of engine is commonly used in commercial airliners?
    1.   Piston engine
    2.   Turbojet engine
    3.   Turbofan engine
11. What is the purpose of the engine's oil system?
    1.   To lubricate the engine's moving parts and keep it cool
    2.   To assist in combustion
    3.   To provide power to the accessories
12. What type of engine is typically used in supersonic aircraft?
    1.   Turboprop engine
    2.   Turbofan engine
    3.   Turbojet engine
13. In a jet engine, which component is responsible for extracting energy from the exhaust gases?
    
    1.   Fan
    2.   Turbine
    3.   Compressor
14. What is the function of the thrust reverser in a jet engine?
    1.   To improve fuel efficiency during cruise
    2.   To redirect exhaust gases forward to reduce the aircraft’s speed during landing
    3.   To increase thrust during takeoff
15. What is the function of the bleed air system in a jet engine?
    1.   To supply compressed air for air conditioning, cabin pressure, and anti-icing
    2.   To increase the engine’s exhaust velocity
    3.   To cool the engine
16. What does "N1" refer to in a turbofan engine?
    1.   The speed of the turbine
    2.   The speed of the compressor
    3.   The speed of the fan
17. What is the function of the engine’s power turbine in a turboprop engine?
    1.   To increase fuel efficiency
    2.   To drive the propeller
    3.   To cool the engine
18. What is the purpose of the FADEC system in modern jet engines?
    
    1.   To manage engine performance and optimize fuel efficiency automatically
    2.   To monitor the temperature of exhaust gases
    3.   To cool the engine during operation
19. What is a key feature of a low-bypass turbofan engine?
    1.   It is more suitable for supersonic flight
    2.   It has a larger proportion of air bypassing the engine core
    3.   It has a smaller fan that produces less thrust
20. What is the typical operational range for a turbofan engine?
    
    1.   Low speeds and high altitudes
    2.   High speeds and low altitudes
    3.   Moderate speeds and moderate altitudes
21. What is a common cause of engine stall?
    
    1.   Rapid changes in airspeed or altitude
    2.   Excessive fuel supply
    3.   Insufficient air intake or compressor failure
22. In a turbofan engine, what is the function of the fan?
    1.   To compress the incoming air for combustion
    2.   To create thrust by accelerating air around the core
    3.   To provide power to the turbine
23. What type of engine is commonly used in small general aviation aircraft??
    
    1.   Turbojet engine
    2.   Turbofan engine
    3.   Turboprop engine
24. What is the primary function of a jet engine?
    
    1.   To generate lift for the aircraft
    2.   To produce thrust by expelling exhaust gases at high velocity
    3.   To convert fuel into mechanical power for propulsion

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