powerplant questions w/ solve (mock exams #1)

powerplant mock exam no.1 sa 1Aero

d

From a standing start with an increase in forward speed jet thrust will
a. Increase
b. Decrease
c. Stay the same
d. Decrease then recover but will never achieve its initial setting

c

One reason for shrouding turbine blades is
a. To reduce ‘creep’ which may occur in the blades
b. To enable thinner blades to be used
c. to improve efficiency and reduce vibration
d. To minimise blade end erosion

a

Bleed air for engine anti-icing is provided by
a. The bleed valves
b. the compressor
c. The turbine stages
d. The combustion chambers

a

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

a

The mixture of impulse and reactin blade shape in the average turbine blade is such that
a. The inner half is impulse and the outer half is reaction
b. The inner half is reactin and the outer half is impulse
c. The leading edge is reaction and the trailing edge is impulse
d. The trailing edge is reaction and the leading edge is impulse

b

Compressor blades increase in size
a. From the root to the tip to increase the temperature
b. From the high-pressure section of the compressor to the low-pressure section
c. From the low-pressure section of the compressor to the high-pressure section to maintain a constant airflow velocity
d. From the tip to the root to decrease the temperature

a

The highest pressure in a gas turbine engine occurs
a. Between the compressor and the combustion chamber
b. In the combustion chamber
c. In the jet pipe
d. at the P1 probe

d

The Has turbine engine uses the principle/s of
a. Newton’s Third Law of motion only
b. Creating thrust equal to the weight of the aircraft
c. Expelling air at the same speed as that of the aircraft
d. Newton’s laws of Motion

a

In a by-pass engine, the by-pass air
a. increases the air mass flow and therefore increases the propulsive efficiency.
b. Cools the combustion chamber and therefore increases the thermal efficiency
c. Reduces the air mass flow and therefore increases the propulsive efficiency
d. Increases the air mass flow and therefore reduces the propulsive efficiency

c

Shrouding of stator blade tips is designed to
a. Prevent tip turbulence
b. Ensure adequate cooling
c. Minimize vibration
d. Prevent tip losses

c

The effect on the temperature and pressure of the gases as they pass across the turbine is
a. Their temperature decreases and their pressure rises
b. Both their temperature and pressure increase
c. Both their temperature and pressure decrease
d. Their temperature increases and their pressure falls

b

The pressure ratio of a gas turbine engine compressor is
a. Equal to the number of compression stages
b. The ratio between compressor outlet and compressor inlet pressure
c. The ratio between exhaust inlet and exhaust outlet pressure
d. Never greater than 5 to 1

b

What is the purpose of the supersonic diffuser in the variable throat intake?
a. Final reduction in velocity prior to compressor face
b. Interim reduction in velocity to below Mach 1 prior to a further reduction in the subsonic diffuser
c. Interim reduction in velocity to below Mach .5 prior to a further reduction in the subsonic diffuser. 
d. Increase in velocity prior to compressor face. 

d

Select the correct order of best propulsive efficiency, from low to high airspeed
a. High by-pass ratio turbo jet, Low by-pass ratio turbo jet, Pure turbo jet, Turbo-prop
b. Low by-pass ratio turbo jet, Pure turbo jet, Turbo-prop, High by-pass ratio turbo jet
c. Pure turbo jet, Turbo-prop, High by-pass ratio turbo jet, Low by-pass ratio turbo jet 
d. Turbo-prop, high by-pass ratio turbo jet, low by-pass ratio turbi jet, Pure turbo jet

d

Which of the following requires the least mass flow rate in order for it to function efficiently?
a. Turbojet
b. Ramjet
c. Scramjet
d. Rocket

a

Cam-ground pistons are installed in some aircraft engines to 
a. Provide a better fit at operating temperatures
b. Act as a compensating feature so that a compensated magneto is not required
c. Equalize the wear on all pistons
d. For proper movement of the connecting rod translated to the movement of piston

a

Which of the following is most likely to occur if an overhead valve engine is operated with inadequate valve clearances?
a. The valve will not seat positively during start and engine warmup
b. The further decrease in valve clearance that occurs as engine temperatures increase will cause damage to the valve-operating mechanism
c. The valves will remain closed for longer periods than specified by the engine manufacturer
d. Timing between the tappet and cam lobe will lessen as it approaches strokes of the piston

b

Compared to normally aspirated engines, turbocharged engine exhaust systems operate at
a. Similar temperatures and higher pressures
b. Higher temperatures and higher pressures
c. Similar temperatures and pressures
d. Lower temperatures and lower pressures

b

What is the purpose of a turbocharger system for a small reciprocating aircraft engine?
a. Compresses the air to hold the cabin pressure constant after the aircraft has reached its critical altitude.
b. Compresses air to maintain manifold pressure constant from sea level to the critical altitude of the engine.
c. Maintains constant air velocity in the intake manifold.
d. Level the engine efficiency while cruising on an altitude above its regular operational capability.

a

Which of the following statements regarding volumetric efficiency of an engine is true?
a. It is possible to exceed 100 percent volumetric efficiency of some engines by the use of superchargers of the proper type.
b. It is impossible to exceed 100 percent volumetric efficiency of any engine regardless of the type of supercharger used.
c. The volumetric efficiency of an engine will remain the same regardless of the amount of throttle opening.
d. Increasing the amount of fuel and air mixture will directly affect volumetric efficiency through the ratio of intake and exhaust volume

c

During engine operation, if carburetor heat is applied, it will
a. Increase air-to-fuel ratio
b. Increase engine RPM
c. Decrease the air density to the carburetor
d. Decrease RPM

a

The primary concern in establishing the firing order for an opposed engine is to

a. Provide for balance and eliminate vibration to the greatest extent possible
b. Keep power impulses on adjacent cylinders as far apart as possible in order to obtain the greatest mechanical efficiency
c. Keep the power impulses on adjacent cylinders as close as possible in order to obtain the greatest mechanical efficiency
d. Create equal distribution of volumetric and thermal efficiency in cylinders

d

Some aircraft engine manufacturers equip their product with choked or taper-ground cylinders in order to
a. Flex the rings slightly during operation and reduce the possibility of the rings sticking in the grooves
b. Increase the compression pressure for starting purposes.
c. Balance the heat applied inside the cylinder during power stroke
d. Provide a straight cylinder bore at operating temperatures

d

Sodium-filled valves are advantageous to an aviation engine because they

a. Are lighter
b. Dampen valve impact shocks
c. Avoid valve deformation
d. Dissipate heat well

c

Excessive valve clearance results in the valves opening
a. Early and closing late
b. Early and closing early
c. Late and closing early
d. Late and closing late

d

For a piston engine, the ratio of the brake horsepower to the indicated horsepower is 
a. Thermal Efficiency
b. Propulsive Efficiency
c. Volumetric Efficiency
d. Mechanical Efficiency

c

A mechanical device used in aircraft reciprocating engine that increases the manifold pressure above the pressure of the atmosphere so as to provide high power output for take-off and to sustain the maximum power at high altitude
a. Afterburner
b. Booster pump
c. Supercharger
d. Generator

b

An un-supercharged aircraft reciprocating engine, operated at full throttle from sea level to 10,000 feet, provided the RPM is unchanged, will 
a. Lose power due to the reduced volume of air drawn into the cylinders
b. Lose power due to the reduced density of the air drawn into the cylinders
c. Produce constant power due to the same volume of air drawn into the cylinders
d. Remains the same as on sea level condition 

c

Heat engines are devices for converting heat into
a. Enthalpy
b. Energy
c. Work
d. Cycles

b

The number of pounds of air present in the engine cylinder per pound of fuel is called 
a. Air specific weight ratio
b. Air-fuel ratio
c. Combustion efficiency
d. Fuel-air mixture

d

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 heat transfer into the engine cycle
c. Increasing the volume of the fuel injected
d. Increasing the engine displacement

c

CP is always greater than CV
a. False
b. it depends
c. True
d. Null

d

For all adiabatic processes between two specified states of a closed system, the net work done is the same regardless of the nature of the closed system and the details of the process. This principle comes from the _____.
a. Second Law of Thermodynamics
b. Zeroth Law of Thermodynamics
c. Third Law of Thermodynamics
d. First Law of Thermodynamics