T 2026 Final-Mock Exam: Aircraft Powerplant

1. Excessive cylinder head temperatures are caused by

A. The prolonged use of rich mixtures.

B. The ignition being too far retarded.

C. The ignition timing being too far advanced.

D. The prolonged use of weak mixtures.

D. The prolonged use of weak mixtures.

2. What occur when a fuel does vaporize quickly?

A. Vapor lock

B. Hard starting

C. Hung starting

D. Backfire

A. Vapor lock

3. A certain gas undergoes a process with the following conditions: initial pressure 400 kPa, initial volume 97 L, final pressure 103 kPa, and final volume 270 L. During the process enthalpy decreases by 35.6 kJ. The specific heats are constant with specific heat at constant volume to 3.58 kJ/kg deg K. Determine the specific heat at constant pressure in kJ/kg deg K.

A. 5.2

B. 6.9

C. 3.1

D. 4.2

A. 5.2

4. One reason for shrouding turbine blades is:

A. To reduce "creep" which may occur in the blades.

B. To improve efficiency and reduce vibration.

C. To enable thinner blades to be used.

D. To minimise blade end erosion.

B. To improve efficiency and reduce vibration.

5. The firing interval of a six cylinder horizontally opposed engine will be:

A. 180

B. 120

C. 60

D. 360

B. 120

6. A 1800 kg car is raised to a height of 2.5 m by hydraulic hoist. The hydraulic pump has a constant pressure of 800 kPa on its piston. How much volume in cubic meter should the pump displace to deliver the required work for lifting the car?

A. 0.015

B. 0.025

C. 0.039

D. 0.055

D. 0.055

7. Hydraulic valve tappets are used on some engines to:

A. Eliminate valve bounce.

B. Eliminate constant valve adjustment and checks.

C. Give a more positive closing action.

D. Give a more positive opening action.

B. Eliminate constant valve adjustment and checks.

8. On which strokes are both valves on a four-stroke cycle reciprocating aircraft engine closed?

A. Exaust and intake

B. Intake and compression

C. Compression and power

D. Power and exhaust

C. Compression and power

9. The length of the stroke is

A. Equal to the length of the cylinder

B. Equivalent to twice the crank throw

C. Inversely proportional to the engine power output

D. Determined by the size of the piston

B. Equivalent to twice the crank throw

10. Valve Overlap is:

A. The number of degrees of camshaft rotation during which the inlet and exhaust valves are open at the same time.

B. The number of degrees of crankshaft movement during which the inlet and exhaust valves are open at the same time.

C. The distance the piston travels while the inlet valve remains open after B.D.C.

D. The number of degrees of crankshaft rotation during which the inlet and exhaust valves are open at the same time around B.D.C.

B. The number of degrees of crankshaft movement during which the inlet and exhaust valves are open at the same time.

11. Determine the jet thrust if the mass flow of the air is 50 lbs/second, the inlet velocity is 734 ft/sec and the jet velocity is 1,300 feet/sec.

A. 878.9 lbs

B. 1,178.8 lbs

C. 978.7 lbs

D. 788.8 lbs

A. 878.9 lbs

12. With an increase in the rotational speed of a four-stroke engine the valve overlap.

A. Remains constant

B. Decreases

C. Increases up to the ground idle and thereafter decreases

D. Increases

A. Remains constant

13. The velocity when the rocket is oxidizing

A. Burnout velocity

B. Splash down velocity

C. Terminal velocity

D. Exhaust velocity

A. Burnout velocity

14. It is a non-air breathing engine that carries its own fuel and oxygen.

A. Rocket

B. Ramjet

C. Pulsejet

D. GTE

A. Rocket

15. A Carnot power cycle operates on 2 lb of air between the limits of 70°F and 500°F. The pressure of isothermal expansion is 400 psia and at the end of isothermal expansion is 185 psig. Determine the following if R= 53.342 (ft-lbf)/(lbm-R). Find the volume at the end of isentropic expansion.

A. 3.56 cu ft

B. 15.67 cu ft

C. 4.36 cu ft

D. 2.83 cu ft

B. 15.67 cu ft

16. The degrees of rotation to complete a full cycle on a nine cylinder engine will be:

A. 180

B. 360

C. 720

D. 80

C. 720

17. Engine ignition system belongs to ATA Chapter ___________.

A. 73

B. 74

C. 75

D. 76

B. 74

18. In a gas turbine engine:

A. Ram pressure is maximum at the start of the take off run.

B. Ram pressure is unaffected by airspeed.

C. Thrust is unaffected by the aircraft's forward speed.

D. Thrust is maximum and ram pressure at minimum at the start of the take off run.

D. Thrust is maximum and ram pressure at minimum at the start of the take off run.

19. Consider a rocket engine. The combustion chamber pressure and temperature are 20 atm and 3,279 deg K respectively. The area of the rocket exit is designed so that the exit pressure exactly equals ambient pressure at a standard altitude of 30 km, where the ambient pressure is 0.01174 atm. For the gas mixture of the fuels, assume that the specific heat ratio is 1.31. The gas constant as 519.6 J/kd-deg K. Calculate the exit Mach number.

A. 5.58

B. 5.77

C. 4.58

D. 3.35

A. 5.58

20. A Carnot cycle operates between the temperature limits of 610 K and 400 K. If the entropy of the low temperature reservoir increases 3.45 kJ/K, determine the work of the cycle.

A. 72450 kJ

B. 534.36 ft-lbf

C. 724.5 kJ

D. 53436.36 ft-lbf

C. 724.5 kJ

21. The turbine blade design in such way that it allows the distribution of the workload throughout the length of the blade.

A. Impulse-reaction

B. Impulse

C. Reaction

D. No reaction

A. Impulse-reaction

22. What is the specific heat ratio of a gas if the ratio of the specific heat at constant pressure and specific gas constant R is 2.357?

A. 1.1

B. 1.42

C. 1.74

D. 1.3

C. 1.74

23. A 1.0 kg steel (Cp = 0.75 kJ/kg-K) rivel cools from 700 K and 400 K upon being installed in a riveted structure. The entropy change in kJ/K of this rivet is:

A. 0.114

B. -0.295

C. 0.346

D. -0.419

D. -0.419

24. Brake Horsepower is:

A. Theoretical power in the cylinder.

B. Useful power at the propeller.

C. Power lost in the engine.

D. Power required to slow the aircraft down.

B. Useful power at the propeller.

25. On aircraft that utilize a constant-speed propeller, its main function

A. Maintain optimum propeller efficiency.

B. Prevent exposure and corrosion of the pitch changing mechanism.

C. Maintain the proper blade angle for certain power setting.

D. Increase the flow of cooling air to the engine nacelle.

A. Maintain optimum propeller efficiency.

26. The effect on the temperature and pressure of the gases as they pass across the turbine is

A. Both their temperature and pressure increase.

B. Both their temperature and pressure decrease.

C. Their temperature increases and their pressure falls.

D. Their temperature decreases and their pressure rises.

B. Both their temperature and pressure decrease.

27. The five events of a four-stroke cycle engine in the order of their occurrence are

A. Intake, compression, ignition, power, exhaust

B. Intake, power, ignition, compression, exhaust

C. Intake, power, compression, ignition, exhaust

D. Intake, ignition, compression, power, exhaust

A. Intake, compression, ignition, power, exhaust

28. A Carnot engine receives 205 kJ of heat from a hot reservoir at 320 deg C and rejects 60 kJ of heat. Calculate the temperature of the cold reservoir.

A. -101.03 C

B. 373.03 K

C. -532.03 F

D. 432.03 R

A. -101.03 C

29. The purpose of the crankcase breather is to

A. Maintain the pressure in the oil tank at atmospheric pressure

B. Prevent distortion of the crankcase

C. Prevent pressure building up inside the crankcase

D. Ease the task of the oil scraper ring

C. Prevent pressure building up inside the crankcase

30. Which is not a cause if the engine is torching?

A. Improper use of mixture control when starting

B. Overpriming

C. Poor ignition

D. Underpriming

D. Underpriming

31. Consider a 1200-kg car cruising steadily on a level road at 90 kph. Now the car starts climbing a hill that is sloped 30 deg upwards from the horizontal. If the velocity of the car is to remain constant during climbing, determine the additional power that must be delivered by the engine.

A. 170 kW

B. 200 kW

C. 197 kW

D. 147 kW

D. 147 kW

32. What is the efficiency of an Otto cycle with a compression ratio of 6:1 the gas is air.

A. 0.512

B. 0.867

C. 0.456

D. 0.765

A. 0.512

33. In a normally aspirated engine, exhaust back pressure:

A. Decreases as an aircraft climbs and thereby reduces the rate of decline of the engine power output.

B. Increases as an aircraft climbs and thereby reduces the engine power output.

C. Is affected by the power lever position.

D. Decreases as an aircraft descends and thereby improves the engine power output.

A. Decreases as an aircraft climbs and thereby reduces the rate of decline of the engine power output.

34. When after burning the jet pipe will:

A. Close to allow for the decreased volume of gas

B. Open to allow for the increased volume of gas.

C. Remain the same

D. Remain the same until the temperature reaches 1700 deg C then open.

B. Open to allow for the increased volume of gas.

35. On a four cylinder engine with a total volume of 9600cc, bore area of 100 cm^2 and a crank throw of 10cm, what would the Compression Ratio be?

A. 7:1

B. 8:1

C. 24:1

D. 6:1

D. 6:1

36. An ideal gas with specific gas constant equal to 395.7 ft-lbf/lb deg R and a ratio of specific heats equal to 1.53, undergoes a reversible constant pressure process during which 465 BTU are added to 4.5 lb of the gas. The initial temperature is 96 deg F. Calculate the change in entropy.

A. 0.63

B. 0.97

C. 0.86

D. 0.79

D. 0.79

37. If the volume of a quantity of gas is halved during compression:

A. Its pressure is approximately doubled.

B. Its temperature remains constant.

C. Its mass is approximately doubled.

D. Its pressure is approximately halved.

A. Its pressure is approximately doubled.

38. An engine has a total volume of 2,100 cm3 and a swept volume of 1,800 cm3. Its compression ratio is:

A. 7:6

B. 6:1

C. 7:1

D. 6:7

C. 7:1

39. In a by-pass engine, the by-pass air

A. Increases the air mass flow and therefore increases the propulsive efficiency

B. Reduces the air mass flow and therefore increases the propulsive efficiency.

C. Cools the combustion chamber and therefore increases the thermal efficiency.

D. Increases the air mass flow and therefore reduces the propulsive efficiency.

A. Increases the air mass flow and therefore increases the propulsive efficiency

40. The Gas Turbine Engine uses the principle/s of

A. Expelling air at the same speed as that of the aircraft

B. Newton's Laws of Motion

C. Creating thrust equal to the weight of the aircraft

D. Newton's Third Law of Motion only

B. Newton's Laws of Motion

41. The temperature of an ideal gas remains constant while the absolute pressure changes from 103.4 kPa to 827.2 kPa. If the initial volume is 80 L, what is the final volume?

A. 0.001 cu m

B. 0.10 cu m

C. 0.01 cu m

D. 1.01 cu m

C. 0.01 cu m

42. The temperature of the gases within the cylinder of a four-stroke engine during the power stroke will

A. Decrease

B. Increase

C. Follow Charles' Law

D. Be constant

A. Decrease

43. Which of the following is not an extensive property?

A. Kinetic Energy

B. Momentum

C. Mass

D. Density

D. Density

44. Equivalent shaft horse power is described as

A. Thrust produced by the propeller minus the residual thrust produced by the turbine

B. Available horsepower on an engine

C. Thrust produced by the propeller plus the residual thrust produced by the turbine

D. Total power loss of an engine

C. Thrust produced by the propeller plus the residual thrust produced by the turbine

45. If the gear ratio is 5:24, what is the speed of the driven gear if the driving gear is rotating at 1000 RPM?

A. 4800 RPM

B. 2408 RPM

C. 180 RPM

D. 208 RPM

D. 208 RPM

46. An engine operating in Diesel Cycle with a compression ratio of 18, and a cut-off ratio of 2.69 produces 400 HP per cycle. Find the heat input in kW.

A. 496

B. 964

C. 539

D. 743

A. 496

47. The mean effective pressure of an ideal air-standard Diesel cycle can be increased by

A. Increasing the size of the intake and exhaust valve

B. Increasing the engine displacement

C. Increasing the volume of the fuel injected

D. Increasing the heat transfer into the engine cycle

B. Increasing the engine displacement

48. The power output of an internal combustion engine can be increased by:

A. Increasing the area of the cylinder.

B. Increasing the length of the stroke.

C. Increasing the engine R.P.M.

D. All of the above.

D. All of the above.

49. Find the thermal efficient of an eight-cylinder Otto engine with a compression ratio of 8 and total volume at TDC of 800 mL taking in atmospheric air at 25 deg C and 100 kPa. The maximum temperature during a cycle is 1600 deg C.

A. 56.47%

B. 89.36%

C. 73.42%

D. 65.45%

A. 56.47%

50. This parameter is constant in a reversible, adiabatic process.

A. Entropy

B. Pressure

C. Temperature

D. Volume

A. Entropy