Module 16 Piston Engine 100 Important Sentences for Revision

 1. Basic Engine Principles

1. A piston engine converts chemical energy into mechanical power.
2. It works on the Otto cycle for spark ignition engines.
3. The four strokes are intake, compression, power, and exhaust.
4. In the intake stroke, the piston moves down drawing in air-fuel mixture.
5. In the compression stroke, the mixture is compressed.
6. The spark plug ignites the mixture near top dead center.
7. The power stroke forces the piston down.
8. The exhaust stroke expels burnt gases.
9. The crankshaft converts linear motion to rotary motion.
10. Engine power depends on displacement and compression ratio.

2. Engine Construction

11. The cylinder head contains valves and spark plugs.
12. The cylinder barrel guides piston movement.
13. The piston transfers gas pressure to the connecting rod.
14. The connecting rod links the piston to the crankshaft.
15. The crankshaft converts reciprocating motion into rotation.
16. Bearings support rotating parts and reduce friction.
17. The camshaft controls valve timing.
18. Pushrods and rocker arms open and close valves.
19. Valve springs ensure proper valve seating.
20. The crankcase houses and supports all major components.

3. Engine Types and Configurations

21. Engines may be inline, opposed, radial, or V-type.
22. Opposed engines are common in light aircraft.
23. Radial engines have cylinders arranged around a crankcase.
24. V-type engines have two banks of cylinders forming a “V” shape.
25. Inline engines are compact and used in smaller aircraft.
26. Radial engines offer good cooling and power-to-weight ratio.
27. Opposed engines are smooth and balanced in operation.
28. Multibank engines improve power output.
29. Turbocharged engines use exhaust gases to increase power.
30. Supercharged engines use mechanical compressors for power boost.

4. Engine Operating Cycles

31. A two-stroke engine completes one cycle in two strokes.
32. A four-stroke engine completes one cycle in four strokes.
33. Four-stroke engines are more fuel-efficient.
34. Two-stroke engines are lighter and simpler.
35. Compression ratio affects efficiency and power.
36. Higher compression ratios increase performance.
37. Detonation occurs when mixture burns uncontrollably.
38. Pre-ignition happens before spark ignition.
39. Both detonation and pre-ignition can damage the engine.
40. Proper fuel grade prevents detonation.

5. Induction and Fuel Systems

41. The induction system delivers air or fuel-air mixture to cylinders.
42. The carburetor mixes air and fuel in correct proportion.
43. Mixture control adjusts fuel flow for altitude changes.
44. Float-type carburetors are common in piston aircraft.
45. Pressure carburetors prevent icing and fuel starvation.
46. Fuel-injection systems deliver fuel directly into intake ports.
47. Fuel injection provides better fuel distribution.
48. Turbochargers use exhaust gases to drive a compressor.
49. Superchargers are driven mechanically by the engine.
50. Induction icing can occur in moist, cold conditions.

6. Ignition System

51. The ignition system provides spark for combustion.
52. Each cylinder has two spark plugs for redundancy.
53. Magnetos generate electrical energy independently.
54. Dual ignition improves reliability and efficiency.
55. The magneto uses rotating magnets to induce current.
56. The distributor sends high voltage to each spark plug.
57. Ignition timing affects engine performance.
58. Early timing can cause knocking.
59. Late timing reduces power and increases heat.
60. Spark plug fouling occurs from lead or carbon deposits.

7. Lubrication System

61. The lubrication system reduces friction and cools parts.
62. Piston engines use either dry sump or wet sump lubrication.
63. In a dry sump, oil is stored in an external tank.
64. Scavenge pumps return oil from the crankcase to the tank.
65. Wet sump systems store oil in the crankcase.
66. Oil coolers maintain correct operating temperature.
67. Filters remove dirt and metal particles.
68. Pressure relief valves prevent excessive oil pressure.
69. Oil viscosity affects flow and lubrication quality.
70. Regular oil checks ensure safe operation.

8. Cooling System

71. Air-cooled engines use fins to dissipate heat.
72. Liquid-cooled engines use coolant circulated through jackets.
73. Baffles direct airflow around cylinders in air-cooled engines.
74. Overheating can cause detonation or piston seizure.
75. Cooling is essential for maintaining performance.
76. Cylinder head temperature is a key indication of cooling efficiency.
77. Oil also assists in cooling internal parts.
78. Proper cowling ensures efficient airflow.
79. Temperature gauges monitor engine heat levels.
80. Poor cooling reduces engine life.

9. Exhaust and Supercharging

81. The exhaust system removes combustion gases.
82. Exhaust manifolds collect gases from cylinders.
83. Mufflers reduce noise and back pressure.
84. Turbochargers increase intake air pressure.
85. Wastegates control turbocharger boost pressure.
86. Superchargers use engine power to compress intake air.
87. Boost pressure must be controlled to prevent damage.
88. Exhaust gas temperature indicates engine performance.
89. Turbo lag occurs due to delayed response of the turbine.
90. Proper maintenance prevents cracks in exhaust systems.

10. Engine Operation and Maintenance

91. Engine start requires correct fuel mixture and ignition.
92. Warm-up allows oil to circulate before high power use.
93. Lean mixture improves fuel economy in cruise.
94. Rich mixture provides cooling during high power.
95. Power checks verify engine performance before flight.
96. Vibration indicates imbalance or misfire.
97. Compression testing checks cylinder sealing.
98. Spark plug inspection ensures proper ignition.
99. Engine overhaul restores components to serviceable condition.
100. Proper operation and maintenance ensure reliability and safety.

 

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Module 15 Gas Turbine Engine 100 Important Sentences for Revision

 1. Basic Principles

1. A gas turbine engine operates on the Brayton cycle.
2. The Brayton cycle consists of intake, compression, combustion, expansion, and exhaust.
3. Thrust is produced by accelerating a mass of air rearward.
4. Newton’s third law is the basis of jet propulsion.
5. The faster the exhaust gases, the greater the thrust.
6. The main sections of a gas turbine are intake, compressor, combustion, turbine, and exhaust.
7. Air enters through the intake with minimum pressure loss.
8. The compressor raises the air pressure.
9. The combustion section adds heat to the compressed air.
10. The turbine extracts energy from hot gases to drive the compressor.

2. Engine Components

11. The intake directs air smoothly into the compressor.
12. The compressor may be centrifugal, axial, or mixed-flow.
13. Centrifugal compressors are common in small engines.
14. Axial compressors are used in large engines for higher pressure ratios.
15. The diffuser slows down air to increase static pressure.
16. The combustion chamber burns fuel continuously.
17. The turbine converts heat energy into mechanical work.
18. The exhaust nozzle accelerates gases to produce thrust.
19. Bearings support rotating shafts.
20. Accessory gearboxes drive pumps and generators.

3. Compressor Section

21. Compressors increase air pressure and temperature.
22. Axial compressors consist of rotating and stationary blades.
23. Rotor blades accelerate the air.
24. Stator blades convert velocity into pressure.
25. Multi-stage axial compressors achieve high pressure ratios.
26. Centrifugal compressors use impeller and diffuser action.
27. Compressor efficiency affects overall engine performance.
28. Surge is a total breakdown of airflow through the compressor.
29. Stall occurs when air separates from the blade surface.
30. Variable stator vanes and bleed valves prevent stall and surge.

4. Combustion Section

31. Combustion occurs at nearly constant pressure.
32. The air-fuel ratio must be correct for complete burning.
33. There are three types of combustion chambers: can, annular, and can-annular.
34. Igniters provide spark during engine start.
35. Fuel injectors atomize and mix fuel with air.
36. The liner directs flame and protects casing from heat.
37. Cooling air flows through liner holes to reduce temperature.
38. Combustion efficiency affects thrust and fuel economy.
39. Flameout occurs when the flame is extinguished during operation.
40. Relight systems restart combustion after flameout.

5. Turbine Section

41. The turbine extracts energy from hot gases.
42. It drives the compressor and accessories.
43. A turbine consists of rotor blades and stator vanes.
44. The stator guides gas flow onto rotor blades.
45. The high-pressure turbine drives the compressor.
46. The low-pressure turbine drives the fan or propeller.
47. Turbine blades are made of nickel-based superalloys.
48. Blade cooling prevents overheating.
49. Cooling air passes through internal passages and holes.
50. Blade creep occurs from long-term high temperatures.

6. Exhaust and Thrust

51. The exhaust system directs gases rearward efficiently.
52. Thrust is created by high-velocity gas exiting the nozzle.
53. Convergent nozzles are used on subsonic engines.
54. Convergent-divergent nozzles are used for supersonic speeds.
55. Afterburners add fuel to the exhaust for extra thrust.
56. Thrust reversers help decelerate the aircraft after landing.
57. Reversers operate hydraulically or pneumatically.
58. Bucket, cascade, and clamshell are main types of reversers.
59. Reverse thrust should not be used in flight.
60. EGT (Exhaust Gas Temperature) is an important performance indicator.

7. Engine Starting and Ignition

61. Starting provides rotation for initial air compression.
62. Air turbine starters are common in large engines.
63. Electrical starters are used on small turbine engines.
64. Ignition systems provide spark for combustion start.
65. Two igniters are used for reliability and redundancy.
66. Igniters use high-voltage discharge.
67. Ignition is required during start and for relight.
68. Exciters store and discharge energy to igniters.
69. After engine self-sustains, the starter disengages.
70. Starter cutout occurs automatically after light-up.

8. Engine Control Systems

71. Engine thrust is controlled by fuel flow.
72. The fuel control unit (FCU) meters correct fuel quantity.
73. FADEC stands for Full Authority Digital Engine Control.
74. FADEC controls fuel and engine parameters electronically.
75. FADEC removes mechanical control cables.
76. Manual reversion may be used in older systems.
77. Power levers command thrust setting to FADEC.
78. Engine control prevents over-speed and over-temperature.
79. EPR (Engine Pressure Ratio) indicates engine thrust.
80. N1 and N2 show compressor spool speeds.

9. Lubrication and Fuel Systems

81. The oil system lubricates and cools engine bearings.
82. Dry sump systems are common in turbine engines.
83. Scavenge pumps return oil to the tank.
84. Filters remove dirt and metal particles.
85. Chip detectors signal metal contamination.
86. Oil coolers maintain correct temperature.
87. The fuel system delivers fuel from tanks to combustion.
88. Boost pumps supply fuel to the engine pumps.
89. Fuel filters remove contaminants.
90. The FCU meters fuel according to throttle position and conditions.

10. Fire Protection, Performance, and Maintenance

91. Fire detection systems use continuous loops or thermal sensors.
92. Overheat detection warns of rising temperature before fire.
93. Fire extinguishing systems use Halon or clean agents.
94. Engine performance is measured by EPR, N1, and fuel flow.
95. Specific fuel consumption defines fuel efficiency.
96. Vibration monitoring detects rotor imbalance.
97. Engine trend monitoring helps predict maintenance needs.
98. Borescope inspection checks internal parts.
99. Engine removal is required for major overhauls.
100. Proper maintenance ensures reliability, safety, and efficiency.

 

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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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