DGCA Module 15 Gas Turbine Engine, 1st Session of 2017 covered engine types, components, operations, performance, starting systems, fire protection and mixed type questions.
DGCA Module 15
1st Session of 2017
1. What is flame stabilization in a gas turbine engine.
A) Helps maintain combustion during engine start only
B) Ensures steady flame during various power settings
C) Increases the velocity of exhaust gases
Answer
2. An impulse turbine works on the principle of.
A) Only pressure drop
B) Only velocity drop
C) Pressure and velocity changes
Answer
3. What is the function of a tail cone in a jet engine.
A) To mount the exhaust nozzle
B) To cool the exhaust gases
C) To reduce turbulence and assist smooth flow
Answer
4. Bearing fitting as per Treager guidelines ensures.
A) Over-tight fit
B) Proper clearance and alignment
C) Lubrication is not required
Answer
5. What does a scavenge pump do in a gas turbine engine.
A) Scavenges used oil from bearing chambers
B) Supplies fuel
C) Cools the exhaust
Answer
6. A thrust reverser is used for.
A) Enhancing cruise speed
B) Reversing the fan airflow to assist deceleration
C) Boosting take-off thrust
Answer
7. Water injection in gas turbine engines is done at.
A) Exhaust cone
B) Combustion chamber only
C) Compressor inlet, diffuser and combustion chamber
Answer
8. A disadvantage of water injection is.
A) Increase in NOx emission
B) Reduces engine thrust
C) Risk of corrosion and compressor blade damage
Answer
9. In an afterburner, pressure ratio.
A) Always increases
B) Always decreases
C) Can increase or decrease based on design
Answer
10. Engine preservation is done to.
A) Increase airflow
B) Maintain engine condition during storage
C) Improve combustion and airflow
Answer
11. Engine cowlings are designed to.
A) Protect internal components and improve aerodynamics
B) Store lubrication oil
C) Serve as firewalls
Answer
12. APU connected directly to load compressor or gas generator means.
A) APU can drive accessories directly
B) APU works only during flight
C) APU functions as a main engine
Answer
13. The starter-generator in a turbine engine connects to.
A) Directly to combustion chamber
B) Reduction gear and load compressor
C) Turbine exit
Answer
14. Free turbine means.
A) Turbine connected to engine core
B) Not connected to any shaft
C) Turbine driving propeller or gearbox independently
Answer
15. The number of bearings in a GTE depends on.
A) Engine thrust only
B) Length and weight of the engine
C) Fuel type
Answer
16. Noise reduction (acoustic treatment) in GTE is used to.
A) Increase engine performance
B) Reduce structural fatigue
C) Minimize environmental and cabin noise
Answer
17. Ignition system using Treager transformer is used for.
A) Low energy discharge
B) Continuous combustion
C) High-energy ignition
Answer
18. Exhaust collector or cone is made of.
A) Rubber
B) High-temperature resistant material
C) Plastic
Answer
19. A disadvantage of air turbine starter is.
A) Requires high-pressure air supply
B) Increases engine thrust
C) Reduces torque
Answer
20. Air impingement starter operates by.
A) Electrical impulse
B) Hydraulic power for engine start emergency
C) High-pressure air directed onto turbine blades
Answer
21. Reverse flow engine layout allows.
A) Shorter engine length and compact design
B) More afterburner space
C) Higher fan bypass ratio
Answer
22. Bearings in a GTE are used to.
A) Support and reduce friction for rotating parts
B) Transmit fuel
C) Measure temperature
Answer
23. In turboprop engines, thrust measurement is done by.
A) Counting RPM
B) Method of torque sensors or shaft rotation
C) Fuel flow rate and shaft rotation
Answer
24. A disadvantage of water-methanol thrust augmentation is.
A) Improves fuel economy
B) Creates thermal stress and corrosion
C) Reduces turbine temperature
Answer
25. Function of fuel oil heat exchanger is to.
A) Cool fuel
B) Increase fuel viscosity
C) Prevent ice by heating fuel using oil
Answer
26. Oil heat sensing using electrically heated Wheatstone bridge detects.
A) Fuel pressure
B) Lubrication oil contamination
C) Oil temperature
Answer
27. Last chance filter in a lubrication system is used.
A) Before oil tank
B) At oil pump
C) Just before oil reaches engine bearings
Answer
28. Seals in turbine engines are used to.
A) Prevent oil leakage and contamination
B) Increase temperature
C) Allow fuel mixing
Answer
29. Engine pressure ratio is defined as.
A) Ratio of intake pressure to exhaust pressure
B) Ratio of turbine to fan speed
C) Ratio of exhaust to intake pressure
Answer
30. Combustion chamber drain points are installed to.
A) Drain unburnt fuel or accumulated fluid
B) Drain lubricating oil
C) Release compressed air
Answer
31. Fire detection systems in turbine engines use.
A) Infrared sensors and continuous loop detectors
B) Water level indicators
C) Oxygen detectors
Answer
32. Jet calibration analyzer is used for.
A) Measuring fuel octane rating
B) Monitoring and analyzing engine fuel flow and performance
C) Checking exhaust emissions
Answer
33. The primary reason turbine blades are fir-tree rooted is to.
A) Prevent axial movement and distribute stress
B) Improve airflow at high speeds
C) Allow faster replacement during overhaul
Answer
34. Which material is commonly used in high-pressure turbine blades due to its creep resistance.
A) Titanium alloy
B) Nickel super alloy
C) Stainless steel
Answer
35. The primary cause of compressor stall is.
A) High EGT
B) Excessive turbine back pressure
C) Disruption of airflow over compressor blades
Answer
36. A can-annular combustor design.
A) Uses one large combustion chamber
B) Uses multiple flame tubes in a ring, sharing air passages
C) Prevents turbine cooling
Answer
37. What is the effect of increasing altitude on engine performance without reheat.
A) Thrust increases
B) EGT increases
C) Thrust decreases
Answer
38. Intercooling in multi-spool compressors is used to.
A) Increase compressor mass
B) Reduce temperature between stages
C) Increase turbine temperature
Answer
39. The purpose of labyrinth seals in gas turbine engines is to.
A) Prevent oil leakage and air mixing
B) Control exhaust gas flow
C) Absorb vibration
Answer
40. The advantage of wide-chord fan blades is.
A) Lower cost
B) Reduced rotational inertia
C) Improved damage tolerance and airflow efficiency
Answer
41. Creep in turbine blades primarily occurs due to.
A) Prolonged high-temperature stress
B) Corrosion
C) Fatigue at high RPM
Answer
42. The swirl vanes in the combustion chamber are responsible for.
A) Directing airflow straight through
B) Creating turbulence for better fuel-air mixing
C) Preventing vortex formation
Answer
43. The first indication of hot start during engine start is.
A) Low RPM
B) Flameout
C) Rapid EGT rise
Answer
44. If the engine experiences compressor surge, the immediate action is to.
A) Increase throttle
B) Activate fuel dump
C) Reduce power/throttle immediately
Answer
45. The working principle of an axial compressor is based on.
A) Conversion of velocity to pressure in stages
B) Expansion in convergent duct
C) Centrifugal acceleration
Answer
46. In FADEC-controlled engines, fuel flow is adjusted based on.
A) Throttle lever angle
B) Oil temperature
C) EGT only
Answer
47. Flame-out during flight can occur due to.
A) High oil pressure
B) Fuel pump surge
C) Crosswind ingestion
Answer
48. The purpose of the EEC in a FADEC system is to.
A) Manually control RPM
B) Electronically manage engine parameters
C) Over-speed the engine
Answer
49. Turbine clearance control system primarily affects.
A) Thrust reversers
B) Oil flow
C) Blade tip clearance
Answer
50. The jet pipe pressure ratio influences.
A) Compressor stability
B) Airflow through fan
C) Thrust output
Answer
51. The EGT sensor is usually located.
A) Before the combustion chamber
B) Between HP and LP turbines
C) After the last turbine stage
Answer
52. Dual-spool engines are more efficient because they.
A) Have fewer moving parts
B) Allow independent operation of LP and HP compressors
C) Operate on ram effect only
Answer
53. A convergent-divergent nozzle is mainly used in.
A) Afterburning engines for supersonic flow acceleration
B) Turbojets operating at subsonic speed
C) Bypass duct of turbofan engines
Answer
54. Bleed air from the engine is used for all except.
A) Cabin pressurization
B) Engine anti-ice
C) Increasing thrust
Answer
55. The LP turbine drives the.
A) Starter motor
B) Fan and LP compressor
C) High-pressure compressor
Answer
56. Stator vanes in axial compressors.
A) Diffuse and direct airflow to rotor blades
B) Diffuse and accelerate airflow to rotor blades
C) Compress air directly
Answer
57. Ceramic coatings on turbine blades are primarily used to.
A) Provide lubrication
B) Increase structural strength
C) Resist high-temperature oxidation
Answer
58. Which of the following contributes most to thrust in a turbofan engine.
A) Core exhaust gases
B) Bypass air from the fan
C) Combustion heat
Answer
59. The purpose of a diffuser in a gas turbine is to.
A) Increase air velocity
B) Decrease air pressure
C) Reduce air velocity and increase pressure
Answer
60. N1 and N2 in a turbofan engine refer to.
A) Fan and gearbox speeds
B) LP and HP spool speeds respectively
C) Two different sensors
Answer
61. Inlet guide vanes are primarily used to.
A) Direct air at proper angle into the first compressor stage
B) Reduce engine RPM
C) Direct air to Provide torque
Answer
62. A reverse flow combustor is beneficial because it.
A) Shortens engine length
B) Increases turbine entry temperature
C) Requires no cooling
Answer
63. A typical axial compressor blade failure is due to.
A) Fuel contamination
B) Oil starvation
C) Foreign object damage (FOD)
Answer
64. Which engine has the highest bypass ratio.
A) Turbojet
B) High bypass turbofan
C) Low bypass turbofan
Answer
65. FADEC prevents engine overspeed by.
A) Using hydraulic stops
B) Electrically controlling fuel supply and VSV
C) Operating bleed valves
Answer
66. High engine vibration at idle may indicate.
A) Fan imbalance
B) Improper fuel control
C) Blade tip erosion
Answer
67. A high EGT during start usually indicates.
A) Low oil pressure
B) Weak igniter
C) Hot start or over-fuelling
Answer
68. Variable stator vanes help in.
A) Directing turbine gas
B) Maintaining compressor stall margin
C) Reducing bypass airflow
Answer
69. Compressor wash is carried out to.
A) Remove metallic debris
B) Cool down the engine
C) Remove salt and soot deposits to improve efficiency
Answer
70. The flame holder in an afterburner is used to.
A) Stabilize flame at subsonic conditions in supersonic flow
B) Stop the flame at subsonic conditions in supersonic flow
C) Mix air and fuel
Answer
71. Spool-up time refers to.
A) The time taken to ignite fuel
B) The time engine takes to reach max RPM from idle
C) Shutdown duration
Answer
72. Turbine cooling air is sourced from.
A) LP turbine exhaust
B) Combustion gas
C) Compressor bleed air
Answer
73. The function of the igniter plug is to.
A) Mix fuel and air
B) Create a continuous spark
C) Provide spark to initiate combustion
Answer
74. In a dual spool engine, the HP turbine.
A) Drives the fan
B) Drives the HP compressor
C) Is not connected to any component
Answer
75. A “hung start” is best described as.
A) EGT exceeds limit
B) Engine RPM stabilizes below idle and fails to accelerate
C) Flameout during spool-up fails to accelerate
Answer
76. The by-pass ratio is defined as.
A) Fan flow / core flow
B) Core mass flow / fan mass flow
C) Turbine mass flow / total flow
Answer
77. High turbine inlet temperature is managed by.
A) Slowing fuel supply
B) Bleed valve control
C) Blade cooling and material selection
Answer
78. Active clearance control uses.
A) Thermocouples control turbine case temperature
B) Fan air or compressor bleed to control turbine case temperature
C) Magnetic sensor
Answer
79. Turboprop engines use propellers to generate.
A) More than 80% thrust
B) Less than 50% thrust
C) All thrust from jet
Answer
80. During engine start, the starter motor is disengaged when:
A) N2 reaches self-sustaining speed
B) EGT stabilizes
C) Fuel flow is complete
Answer
81. Compressor bleed valves are used during start-up to.
A) Increase airflow
B) Prevent compressor surge
C) Reduce noise and Increase airflow
Answer
82. What component meters fuel to the combustion chamber in a FADEC engine.
A) Manual fuel lever
B) Fuel control unit
C) Fuel metering valve
Answer
83. A typical EEC failure results in.
A) Complete shutdown
B) Automatic reversion to manual control or alternate mode
C) Increased vibration and automatic control manual or alternate mode
Answer
84. Engine pressure ratio (EPR) is calculated using.
A) Compressor inlet pressure / turbine inlet pressure
B) Exhaust pressure / intake pressure
C) Fan pressure / core pressure
Answer
85. Which inspection method is used for blade root cracks.
A) Visual
B) Ultrasonic
C) Fluorescent penetrant inspection
Answer
86. Sudden engine flameout at altitude can be caused by.
A) Volcanic ash ingestion
B) Compressor fouling
C) High humidity
Answer
87. The primary failure risk in a turbine disk is due to.
A) High-cycle fatigue from RPM fluctuations
B) corrosion and faults
C) Fuel impurities
Answer
88. Ram air in turbofan engines contributes to.
A) Engine cooling and pressurization system
B) EGT increase
B) Engine cooling and Turbine rotation
Answer
89. The function of the pressure ratio transmitter is to.
A) Regulate N1
B) Compare engine inlet and exhaust pressures
C) Open bleed valves and exhaust velocity
Answer
90. Which gas turbine component experiences the highest thermal stress.
A) HP turbine blades
B) Combustion liner
C) Fan casing
Answer
91. Fan blade-out containment systems are designed to.
A) Increase thrust and Reduce EGT
B) Catch broken blades and prevent fuselage damage
C) Both
Answer
92. The purpose of variable nozzle area in afterburners is to.
A) Maintain correct back pressure during reheat operation
B) Allow cooling during reheat operation
C) Bypass hot gases
Answer
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