Aircraft Powerplant 2019 Board Exam

  1. A certain spring, when stretched, measures 15.5 cm requiring a work of 565 joules to do it. Its free length is 5.4 cm. What is the spring constant (in kN/m)?

·       42.7

·       50.1

·       47.2

·       53.5

  1. What is the function of turbines located at the rear section of a gas‑turbine engine?

·       Increase air velocity

·       Drive the compressor section

·       Expand air pressure

·       Drive the combustion chamber

  1. What do you call the power produced by turboprop engines?

·       Equivalent shaft horsepower

·       Mechanical power

·       Delivered horsepower

·       Indicated horsepower

  1. In a certain location, the barometer reads 13.45 psi and a pressure gage reads 86 psig. Solve for the absolute pressure in inches of mercury.

·       238

·       203

·       217

·       225

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

·       5.2

·       6.9

·       3.1

·       4.2

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

·       4800 RPM

·       2408 RPM

·       130 RPM

·       208 RPM

  1. Consider a rocket engine. The combustion‑chamber pressure and temperature are 20 atm and 3,279 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 0.01147 atm. For the gas mixture of the fuels, assume the specific heat ratio is 1.31. The gas constant is 519.6 J/kg‑K. Calculate the exit Mach number.

·       5.58

·       5.77

·       4.58

·       3.35

  1. The length of the piston movement in a reciprocating engine is called

·       travel

·       bore

·       radial

·       stroke

  1. A cycle that consists of two isothermal and two isobaric processes is called

·       Ericsson cycle

·       Carnot cycle

·       Brayton cycle

·       Sterling cycle

  1. Calculate the pressure (in kPa) at the start of power stroke of an internal‑combustion engine, assuming the specific heats and gas constant for the fuel‑air mixture are approximated by the air values alone. The temperature at the start of power stroke is 3,490 K. The temperature at the end of the compression stroke is 550 K, and the pressure at the end of the compression stroke is 15.5 atm.

·       9,966

·       9,725

·       9,001

·       9,335

  1. Which of the following defines a compressor stage?

·       Air pressure increased by 100%

·       Air passes through a fan then a stator

·       Air passes through a stator then a rotor

·       Air pressure decreased by 50%

  1. A large stone with mass 5 kg is thrown with a constant acceleration from rest to 25 km/h in 5 s. Calculate the acceleration (in m/s²).

·       1.3

·       3.0

·       2.6

·       1.4

  1. A thermometer reads 418°F. What is the reading in °C?

·       856.3

·       623.4

·       456.8

·       214.4

  1. A double‑acting 35.56 cm × 35.56 cm compressor is rotating at 100 rpm. What is the displacement volume (m³/min)?

·       4.032

·       7.063

·       5.021

·       8.072

  1. The thrust produced by a rotating propeller is a result of

·       the angle of attack of a propeller and plane of rotation

·       an area of decreased pressure immediately in front of the propeller blades

·       an area of low pressure behind the propeller blades

·       the angle of relative wind and rotational velocity of the propeller

  1. By experience, it has been found that if the compression ratio of the internal‑combustion engine is much greater than 10:1, what may occur?

·       Implosion

·       Combustion

·       Preignition

·       Pulsing

  1. What publication is used for guidance to determine whether a powerplant repair is major or minor?

·       Pilot’s handbook

·       Airworthiness Directives

·       Aircraft owner’s manual

·       14 CFR 43

  1. (1) During takeoff, propeller thrust is greatest if the blade angle of attack is low and the engine power setting is high.
    (2) With the aircraft stationary, propeller thrust is greatest if the blade angle of attack is high and the engine power setting is high.
    Regarding the above statements:

·       Only No. 1 is true

·       Only No. 2 is true

·       Both No. 1 and No. 2 are true

·       Neither statement is true

  1. Which thrust rating is allowed for a limited time only?

  • Maximum take‑off thrust

  • Maximum climb thrust

  • Maximum cruise thrust

  • Maximum idle thrust

  1. Consider a rocket engine. The combustion‑chamber pressure and temperature are 20 atm and 3,279 K respectively. For the gas mixture of the fuels, assume the specific heat ratio is 1.31. Calculate the specific heat at constant pressure (J/kg‑K) if the gas constant is 519.6 J/kg‑K.

·       2,357

·       2,196

·       2,299

·       2,463

  1. Consider an airplane powered by a turbojet engine, flying at a standard altitude of 29,000 ft at a velocity of 455 miles/hr. Calculate the pressure (lb/ft²) at the altitude at which the aircraft is flying.

·       682

·       658

·       677

·       669

  1. If the intake valve is open too early in the cycle of operation of a four‑stroke cycle engine, it may result in

·       backfiring into the induction system

·       engine quit

·       improper scavenging of exhaust gases

·       engine kickback

  1. A fluid is under a pressure of 15.5 lb/in² and a temperature of 266°F. Find the velocity of sound (ft/s) in the fluid if the fluid is air.

·       1,121

·       1,321

·       927

·       1,556

  1. The recommended aircraft engine lubricants are

·       vegetable, mineral or synthetic based

·       animal, mineral or synthetic based

·       animal and vegetable based

·       mineral or synthetic based

  1. Find the absolute pressure inside a cylinder that reads 60 psig with a Hg manometer reading 76.2 cm.

·       65.3 psia

·       74.7 psia

·       14.7 psia

·       100 psia

  1. Which feature distinguishes the exhaust valve from the intake valve of a reciprocating engine?

·       Exhaust‑valve side has no cooling fins

·       Intake valves have short stem

·       Exhaust valves are hollow

·       Intake valves have large diameter

27.    The maximum power is normally considered to be developed in a reciprocating engine with a fuel/air mixture of approximately

·       10:1

·       12:1

·       8:1

·       15:1

28.    Which of these conditions will cause an engine to have an increased tendency to detonate?
(1) High manifold pressure
(2) High intake‑air temperature
(3) Engine overheated
(4) Late ignition timing

·       1,4

·       1,2,3

·       3,4

·       1,2,3,4

29.    What operational force tends to increase propeller blade angle?

·       Centripetal force

·       Thrust bending force

·       Centrifugal twisting force

·       Aerodynamic twisting force

30.    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 liters, what is the final volume?

·       0.001 m³

·       0.10 m³

·       0.01 m³

·       1.01 m³

31.    Engine pressure ratio is determined by

·       Multiplying engine inlet total pressure by turbine outlet total pressure

·       Dividing engine inlet total pressure by turbine outlet total pressure

·       Multiplying turbine outlet total pressure by engine inlet total pressure

·       Dividing turbine outlet total pressure by engine inlet total pressure

32.    What type of oil system is usually found on turbine engines?

·       Dry sump, dip and splash

·       Dry sump, pressure and spray

·       Wet sump, pressure and splash

·       Wet sump, spray and splash

33.    An ideal gas with specific‑gas constant 395.7 ft‑lb/lb‑°R and ratio of specific heats 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°F. Calculate the change in entropy (Btu/°R).

·       0.63

·       0.97

·       0.86

·       0.79

34.   Given the propulsive efficiency , where  is exhaust or jet velocity and  is free‑stream velocity. A propeller produces thrust by a large mass flow rate with a small ; therefore  is

·       high

·       low

·       zero

·       constant

35.    Liquid‑propellant rockets have what kind of tanks to store fuel and oxidizer?

·       High volume

·       Low pressure

·       High pressure

·       Insulated

36.    The conditions at the beginning of compression in an Otto engine operating on hot‑air standard, , are 101.3 kPa, 0.038 m³ and 32°C. Clearance is 10% and 12.6 kJ of heat is added per cycle. Determine  and cycle efficiency.

·       204 kPa, 56%

·       200 kPa, 90%

·       300 kPa, 47%

·       450 kPa, 68%

37.    The force that can be produced by an actuating cylinder whose piston has a cross‑sectional area of 3 in² operating in a 1000‑psi hydraulic system is most nearly

·       1500 lb

·       1000 lb

·       500 lb

·       3000 lb

38.    A Carnot cycle operates on air as an ideal gas with constant specific‑heat ratio. At the start of isothermal expansion, its data are: 250 lb/sq in abs, 4 ft³, and 500°F. The ratio of isothermal expansion  and the isentropic compression ratio . Find the temperature (°R) at the end of the isentropic expansion process.

·       930

·       950

·       960

·       940

39.    A cat climbs up a tree and cannot climb down. The cat weighs 2.5 N. Assuming sea‑level conditions, if the potential energy of the cat with respect to the ground is 125 J, how high is the cat from the ground (ft)?

·       16.4

·       8.2

·       9.5

·       10.5

40.    A bowling ball of mass 2 kg is thrown with constant acceleration from rest to 18 km/h in 3 s. Calculate the acceleration (m/s²).

·       1.67

·       2.85

·       1.28

·       2.49

41.    At what speed must a crankshaft turn if each cylinder of a four‑stroke cycle engine is to be fired 200 times a minute?

·       800 RPM

·       200 RPM

·       400 RPM

·       1600 RPM

42.    Which component of the lubrication system triggers a warning when system pressure drops below a specified level?

·       The pressure switches

·       The bypass filters

·       The pressure transmitter

·       The pressure gage

43.    A thermometer reads 521°F. What is the reading in °R?

·       980.67

·       449

·       1085

·       745

44.    How do you assess the following statements regarding oil cooling in a gas‑turbine engine?
A – Fuel may be used to cool oil in gas‑turbine engines.
B – Ram air may be used to cool oil in gas‑turbine engines.

·       Both A and B are correct

·       Only B is correct

·       Only A is correct

·       Both A and B are incorrect

45.    Turbojet and turbofan thrust‑reverser systems are generally powered by

·       fuel pressure, hydraulic pressure, pneumatic pressure

·       fuel pressure, electricity, hydraulic pressure

·       electricity, hydraulic pressure, pneumatic pressure

·       fuel pressure, electricity, pneumatic pressure

46.    Turbine blades are generally more susceptible to operating damage than compressor blades because of

·       engineering design problem

·       high pressure and high velocity of gas flow

·       higher centrifugal loading

·       exposure to high temperatures

47.    Propeller blade angle is the angle between chord of the blade and the

·       axis of rotation

·       rotational plane of the propeller

·       relative wind

·       angle of attack of the airfoil

48.    A turbine operator under steady flow is receiving steam at 33.3 m/s. What is the change in kinetic energy if the steam leaves the turbine at 100 m/s? Express the answer in kJ/kg.

·       4.446

·       3.571

·       7.002

·       5.306

49.    When an engine with a subsonic divergent‑type inlet duct is running in place at high speed on the ground, the air pressure within the inlet is

·       positive

·       zero

·       ambient

·       negative

50.    Which of the following directly affects the rocket engine’s thrust?

·       Exhaust temperature

·       Inlet velocity

·       Exit velocity

·       Pressure ratio