Worksheetspower plant 1-113
Total questions: 113
Worksheet time: 57mins
The temperature of the gases within the cylinder of a four-stroke engine during the power stroke will:
be constant
decrease
increase
follow Charles's Law
The number of revolutions of the crankshaft required to complete a full cycle in a four-stroke engine is:
6
4
2
8
The inlet valve opens before TDC in the exhaust stroke to:
increase the pressure in the cylinder on completion of the induction stroke.
reduce engine vibration
allow the incoming mixture to mix with a certain proportion of the exhaust gases
induce a greater amount of mixture into the cylinder
The correct working cycle of a four-stroke engine is:
exhaust, power, induction, compression
compression, power, exhaust, induction
induction, power, compression, exhaust
power, exhaust, compression, induction
Valve overlap is incorporated in the valve timing of a piston engine to:
improve volumetric efficiency
reduce wear on the big end bearings
increase the engines compression ratio
prevent a weak cut when the engine is accelerated rapidly
When the spark ignites the mixture:
the explosion pushes the piston down
the mixture changes from rich to weak forward of the flame front
complete combustion occurs within 8 to 10 microseconds
temperature and pressure increase within the cylinder
With an increase in outside air temperature, specific fuel consumption will:
increase
decrease
stay the same
stay the same for all temperatures up to and including 15°C and thereafter increase
During the compression stroke:
the temperature of the gases remains constant
the volume of the gases increases
the mass of the mixture decreases
the mass of the mixture remains constant
During the induction stroke:
the mixture becomes weaker
the volume of the gases becomes smaller
the temperature of the gases reduces
the pressure of the gases increases
The power output of an internal combustion engine:
is proportional to the volume of mixture induced into the cylinder
increases with increased humidity
falls as the charge temperature falls
is proportional to the weight of the mixture induced into the cylinder
During the period of valve overlap:
the action of the exhaust gases flowing past the exhaust valve increases the pressure within the cylinder
the temperature of the exhaust gases increases the mass of incoming mixture
the action of the exhaust gases flowing out past the exhaust valve tends to reduce the pressure in the cylinder
the crankshaft is moving past Bottom Dead Centre
Valve Overlap is:
the number of degrees of camshaft rotation during which the inlet and exhaust valves are open at the same time
the number of degrees of crankshaft movement during which the inlet and exhaust valves are open at the same time
the distance the piston travels while the inlet valve remains open after BDC
the number of degrees of crankshaft rotation during which the inlet and exhaust valves are open at the same time around BDC
The purpose of a valve spring is to:
close the valve
cause a snap opening of the valve
allow the valve timing to vary with changing rpm
maintain the valve clearance within tolerance
A reduction gear is fitted:
between the camshaft and the propeller
between the pushrods and the valves
between the crankshaft and propeller
between the connecting rod and the crankshaft
Two valve springs are fitted to each valve:
to minimize camshaft wear
to allow a greater cam rise
to prevent valve rotation
to reduce valve bounce
Excessive valve clearance:
will prevent the valve closing completely
is eliminated when the engine reaches working temperature
will cause the valve to open early and close late
will cause the valve to open late and close early
Valve lead occurs when:
the inlet valve opens before bottom dead centre
the exhaust valve opens before the inlet valve
the exhaust valve opens before top dead centre
the inlet valve opens before top dead centre and the exhaust valve opens before bottom dead centre
The length of the stroke is:
equal to the length of the cylinder
determined by the size of the piston
equivalent to twice the crank throw
inversely proportional to the engine power output
The number of revolutions required to complete the induction and compression stroke in a six cylinder four-stroke engine is:
1
2
6
4
The purpose of a crankcase breather is to:
maintain the oil tank pressure at atmospheric
prevent distortion of the crankcase
allow the oil to breathe
prevent pressure building up inside the crankcase
Piston rings are manufactured from cast iron:
because it has a negative coefficient of expansion
to take advantage of its extreme malleability
because of its self-lubricating qualities
to take advantage of its brittleness
The thermal efficiency of a piston engine can be increased by:
increasing the rpm
increasing the combustion chamber volume
advancing the ignition point into the direction of rotation
increasing the compression ratio
A normally aspirated engine is one which:
has four cylinders
is not supercharged
is never air-cooled
is all of the above
The Compression Ratio of an engine may be defined as the:
swept volume + clearance volume ÷ swept volume
swept volume + clearance volume ÷ clearance volume
total volume - clearance volume ÷ clearance volume
swept volume ÷ (swept volume + clearance volume)
Specific Fuel Consumption (SFC)
is the inability of the internal combustion engine to use any fuel other than that specified by the manufacturer
becomes greater as the efficiency of the engine improves
is the weight of fuel used by an engine per unit horsepower per unit time
increases in proportion to the thermal efficiency
Brake Horsepower is:
theoretical power in the cylinder
useful power at the propeller
power lost in the engine
power required to slow the aircraft down
A method of improving Volumetric Efficiency is:
valve overlap
the use of carburettor heat
weakening the mixture
to make the mixture richer
From the following list select the correct combination of statements. The primary tasks of lubrication are to: 1. reduce friction, 2. cool the engine, 3. clean the engine, 4. reduce component wear, 5. act as a hydraulic medium
1 and 3.
2 and 5.
1 and 4.
1 and 5.
In a piston engine dry sump oil system, the oil temperature and pressure are sensed:
when the oil is leaving the sump.
for the temperature when the oil is leaving the tank, and for the pressure when the oil is leaving the pressure pump.
for the oil temperature when the oil is entering the tank and for the pressure when it is entering the pressure pump.
at the same point.
Oil returning to the oil tank is filtered by:
the oil pressure filter.
the oil tank filter.
a micron size multi-bore filters assembly.
the scavenge filter.
Engine oil pressure is:
low at idle rpm and high at high rpm.
controlled by the oil cooler.
substantially decreased when the oil pressure relief valve opens.
relatively unaffected by engine speed.
The purpose of the crankcase breather is to:
maintain the pressure in the oil tank at atmospheric pressure.
ease the task of the oil scraper ring.
prevent pressure building up inside the crankcase.
prevent distortion of the crankcase.
The most probably cause of small fluctuations in the oil pressure would be:
lack of oil.
the pressure relief valve sticking.
air in the oil tank.
the scavenge pump working at a greater capacity than the pressure pump.
The scavenge pump system in a lubrication system has:
a bypass in case of blockage.
a smaller capacity than the pressure pump.
a bifurcated tertiary drive system.
a larger capacity than the pressure pump.
In a "wet sump" oil system, the oil is contained in the:
engine and tank.
tank and oil cooler.
sump and tank.
engine and sump.
The oil contents of a piston engine (wet sump) are checked:
when the engine is running at idle power.
as soon as possible after the engine has stopped because the oil will drain away from the sump.
after approximately 15 minutes once the engine has stopped.
when the oil has reached a specific temperature.
The most efficient method for cooling a piston engine is to use .................... However, the most common method of cooling is to use ................. because of the ................ involved.
air cooling liquid cooling reduced costs
liquid cooling air cooling reduced costs
fuel cooling air cooling reduced costs
liquid cooling fuel cooling reduced costs
The device utilized to measure temperature on a piston engine is:
thermometer
barometer
thermocouple
thermostat
The spark appears at the plug electrodes when:
the contact breaker closes
the contact breaker opens
the contact breaker stays open
the magneto switch is made
The ignition switch is fitted in:
the primary coil circuit
the secondary coil circuit
the engine starter motor circuit
the battery circuit
When the ignition switch is placed in the 'ON' position it:
isolates the breaker points
makes the engine starter motor circuit
'Earths' or 'grounds' the secondary winding
breaks the primary to earth circuit
The purpose of a condenser as fitted in a magneto is:
to assist in the rapid collapse of the primary current and prevent arcing at the contact breaker points
to prevent the rapid collapse of the primary circuit and arcing at the points
to reduce the high tension voltage of the secondary circuit
to earth the primary circuit
The engine is checked for dead cut at:
a power check
slow running
cruising rpm
full throttle
The distributor directs:
voltage from the primary winding to the spark plug
voltage from the secondary winding to the primary winding
voltage from the magneto secondary winding to the spark plug
voltage from the secondary winding to the contact breaker
The purpose of an ignition switch is:
to control the primary circuit of the magneto
to prevent condensation
to connect the secondary coil to the distributor
to connect the battery to the magneto
In a complex engine as rpm increases the ignition timing may be:
advanced
retarded
not altered
only retarded
An impulse starter is a device to assist in starting an engine which uses:
a leaf spring
a coil spring to increase temporarily the speed of rotation of the magneto
a special starting battery which provides a sudden impulse of electricity to the plugs
an explosive inserted in a special tube
A fuel grade which is used in typical aircraft engines is:
DTD. 585/100
DERD 2479
AVGAS 100
DERD 2484
In the internal combustion engine, detonation occurs due to:
the use of too high an rpm with too little manifold pressure
the use of the wrong grade of oil
the cylinder temperatures and pressures being too low
excessive combustion temperatures and pressures
The calorific value of a fuel is the:
kinetic energy contained within it
heat energy in the fuel
heat energy required to raise the temperature of the fuel to its boiling point
heat energy required to raise the temperature of the fuel to its boiling point from absolute zero
If the vent pipe of an aircraft's fuel tank becomes blocked, it will cause:
the pressure in the tank to fall when fuel is used
the pressure in the tank to rise when fuel is used
the evaporation rate of the fuel to decrease as fuel is used from the tank
the fuel pressure at the carburettor to rise
Detonation is liable to occur in the cylinders:
with an over rich mixture at idle power
with a weak mixture and high cylinder head temperature
with a rich mixture at high power settings
at very low engine speed
Pre-ignition refers to the condition when:
a rich mixture is ignited by the spark plug
the spark plug ignites the mixture too early
the mixture is ignited by abnormal conditions within the cylinder before the normal ignition point
the mixture burns in the inlet manifold
Flame Rate is the term used to describe the speed at which:
the mixture burns within the cylinder
the combustion pressure rises within the cylinder
peroxide forms within the cylinder
fulminates form with the cylinder
The colour of 100/130 grade low lead fuel is:
green
blue
red
straw yellow
Weakening the mixture below the best fuel/air ratio will cause the engine power to:
decrease
increase initially, but decrease below take off power
increase
be unaffected by altitude increase
For maximum endurance the mixture control should be set to:
weak
the chemically correct state
between rich and weak
rich
An air/fuel ratio of 9:1 would be considered:
chemically correct
extravagant
rich
weak
Because of the reduction in the density of the atmosphere associated with an increase in altitude:
the mixture control must be moved towards the weak position
the throttle must close progressively to maintain the best air/fuel ratio.
the mixture must be progressively richened to compensate for the power loss
the octane rating of the fuel must be increased
A chemically correct mixture is:
15:1 (fuel : air)
15:1 (air : fuel)
13:1 (fuel : air)
13:1 (air : fuel)
While weakening the mixture from the chemically correct mixture the EGT will ........ and the cylinder head temperature will ........ with a ........ in thermal efficiency.
increase increase decrease
decrease increase decrease
decrease increase increase
increase increase increase
Which of the following mixtures theoretically would produce the maximum rpm?
14:1 (air : fuel)
14:1 (fuel : air)
15:1 (fuel : air)
15:1 (air : fuel)
A weak mixture is used for which of the following?
Take-off
Climbing
Engine starting
Cruising
While using a weak mixture which of the following would be an incorrect statement?
The charge would be cooled due to a larger proportion of nitrogen in the cylinder
The charge would burn slower due to a larger proportion of nitrogen in the cylinder
The ignition may have to be advanced
The ignition may have to be retarded
While using a rich mixture which of the following would be a correct statement?
The charge would burn slower
All of the fuel would be used during combustion
All of the oxygen would be used during combustion
Cylinder head temperature increases while richening further
The pressure in the induction manifold of a normally aspirated engine:
remains constant as the throttle is opened
decreases as the throttle is opened
initially increases as the throttle is opened but decreases after approximately the half open position
increases as the throttle is opened
The purpose of an accelerator pump is to:
assist in the atomization of the fuel before it leaves the discharge nozzle
prevent a rich cut when the throttle lever is advanced rapidly
prevent dissociation and detonation
prevent a weak cut when the throttle lever is advanced rapidly
The fuel flow to a piston engine will vary according to:
the rpm and the throttle position only
the rpm, the throttle position and the mixture setting
the rpm and the mixture setting only
the rpm only
The primary function of a diffuser in a carburettor is to:
control the mixture strength over part of the engine speed range
vent air from the float chamber
emulsify the fuel during engine acceleration
enable adjustment of the engine slow running speed
The Venturi in the carburettor choke tube creates:
a positive pressure over the discharge nozzle
a depression over the fuel discharge nozzle
a positive pressure at the throttle valve
a decrease in the velocity of the air entering the engine
The fuel priming pump supplies fuel directly to:
the throttle butterfly valve
the exhaust manifold
the induction manifold
the inside of the combustion chamber in the region of the spark plug
A weak mixture would be indicated by:
a drop in engine speed
white smoke in the exhaust manifold
detonation and black smoke from the exhaust
an increase in engine speed with black smoke from the exhaust
The presence of an engine driven fuel pump on an engine fitted with a carburettor:
dispenses with the need for a carburettor float chamber
ensures a positive flow of fuel to the discharge nozzles
ensures a positive flow of fuel to the carburettor float chamber
dispenses with the need for a fuel priming system
It would normally be considered dangerous to pump the throttle lever when starting an engine because:
it could increase the risk of fire in the carburettor air intake
it would prevent the engine starting
the engine would start too rapidly
it would richen the mixture to the point where spontaneous combustion would occur in the combustion chamber
Excessive cylinder head temperatures are caused by:
the prolonged use of weak mixtures
the ignition timing being too far advanced
the prolonged use of rich mixture
the ignition being too far retarded
The mixture supplied by the carburettor to the engine is said to be weak when:
the proportion of air in the mixture is insufficient to allow full combustion of the fuel
the proportion of air in the mixture is greater than that needed for full combustion of the fuel
a grade of fuel lower than that specified for the engine is used
there is insufficient power in the engine for take off
In an attempt to maintain the correct air/fuel ratio while climbing into the decreased density air of higher altitude:
the valve timing can be changed
an accelerator pump can be fitted
a mixture control is used
a diffuser is fitted
The greater the weight of combustible mixture in the cylinders:
the weaker is the mixture
the more the power decreases
the lower the cylinder head temperature will be
the greater the power developed by the engine
A rich mixture is supplied to the cylinders at take-off and climb:
to give greater thermal efficiency
to cool the charge temperature and prevent detonation
to increase the volumetric efficiency
to give excess power
A fuel strainer should be fitted:
in the inlet manifold
at the air intake
before the main jet
after the main jet
The correct air/fuel ratio for an engine running at idle is:
weak
chemically correct
16:1
rich
The method of priming an engine not fitted with a priming pump is to:
activate the mixture control lever several times
turn the engine over several times on the starter motor before selecting the ignition on
pump the throttle several times
position the throttle lever midway between open and close
When an engine is fitted with a fuel injection system:
it does not require priming.
a separate priming system must be fitted.
a separate priming system is not required.
priming fuel originates from the excess supplied from the engine driven pump.
The mixture control on an engine fitted with fuel injection is:
automatic.
operated by a pneumatic plunger system.
hydro-pneumatically operated.
necessary.
In the intake of a fuel injected engine:
there will be a throttle valve but no Venturi.
neither a throttle valve nor a Venturi is required.
there will be a Venturi but no throttle valve.
both a throttle valve and a Venturi are required.
The discharge nozzle injects fuel:
continuously into the inlet manifold as close to the inlet valve as possible.
into the inlet manifold when the inlet valve opens.
into the combustion chamber during the compression stroke.
continuously into the combustion chamber during the induction stroke.
The Fuel Control Unit meters fuel to the discharge nozzles in proportion to:
the position of the throttle valve only.
the position of the mixture control lever only.
the positions of both the throttle lever and the mixture control lever.
the number of strokes applied to the priming pump.
The discharge nozzles of a fuel injected engine are matched to:
supply exactly the same amounts of fuel as each other.
the type of engine they are fitted to.
the octane rating of the fuel supply.
the engine they are fitted to and to the nozzles on the other cylinders.
A fuel injected engine can be primed by:
a manual priming pump which delivers fuel to the discharge nozzles.
an electric fuel pump delivering fuel to the discharge nozzles.
the excess fuel delivered by the engine driven fuel pump.
pumping the throttle lever while turning the engine over on the starter motor.
The fuel manifold valve:
meters the amount of fuel delivered to the engine in proportion to the amount of air being delivered to the engine.
distributes fuel to each cylinder in the correct firing order.
distributes fuel continuously to all of the cylinders continuously.
is kept entirely separate from the priming system.
An engine which is fitted with fuel injection:
will never encounter hydraulicing.
will not suffer from refrigeration icing.
cannot be started by swinging the propeller.
does not require priming.
The Common Rail:
is, in effect, a reservoir of high pressure fuel
is, in effect, a reservoir of low pressure fuel.
is a device common to both the fuel and lubrication systems.
is a device common to both the ignition and lubrication systems.
The Manifold Pressure Gauge fitted to a supercharged engine measures:
the absolute pressure in the induction manifold
the differential pressure across the supercharger compressor
the ratio between the atmospheric pressure and the cam rise at the supercharger inlet
the pressure upstream of the throttle valve
The use of a turbocharger on an engine will:
improve the exhaust scavenging efficiency
raise the volumetric efficiency of the engine
cause an automatic rise in the engine rpm as altitude is gained
cause an automatic rise in engine power as altitude is gained
The speed of the turbine of a turbocharger is controlled by:
the diversion of exhaust gases
controlling the exit of the exhaust gas passing out of the eye of the impeller
the use of a variable controller
an automatic gearbox positioned between the turbine and the impeller
The turbocharger bearing is lubricated and cooled by:
its own internal self-contained oil system
the engine oil
a total loss system
a tapping in the scavenge oil system
The purpose of an intercooler is:
to minimize the risk of detonation
to increase the volume of the charge
to decrease the density of the charge
to prevent overheating of the exhaust manifold
The function of a diffuser in a supercharger is:
to decrease the temperature and increase the velocity of the charge
to increase the velocity and decrease the pressure of the charge
to decrease the velocity and decrease the pressure of the charge
to decrease the velocity and increase the pressure of the charge
Air enters the compressor of a turbosupercharger:
at the tip and passes across the impeller blades to exit at the eye
at the diffuser and exits at the impeller
at the eye and passes across the diffuser blades before exiting at the impeller tip
at the eye and passes across the impeller blades to exit at the tip
With a turbocharger installed on the engine, its exhaust back pressure:
remains the same
is decreased
is increased
decreases in the climb
A high performance supercharger may require an intercooler to be placed:
between the supercharger and the inlet valve
at the carburettor intake
between each cylinder
between the engine block and the exhaust manifold
With an increase of compressor discharge pressure the fuel flow will:
increase
remain constant
decrease
increase, but only in proportion to altitude increase
A turbocharger's rotational speed is determined by:
the diversion of exhaust gas
the position of the throttle valve
the density of the air at the compressor intake
bleeding off excess exhaust pressure
During take-off from a sea level airfield with ISA conditions, the position of the wastegate of a turbocharged engine is:
fully open
almost fully open
controlled by the throttle position
fully closed
Maximum Continuous Power (MCP) is:
unrestricted, but only if economical cruising power is set
the maximum power the engine will give at any time
given a 5 minute limitation
unrestricted
The primary purpose of a supercharger is to:
raise the temperature of the charge entering the cylinder
increase the mass of the charge entering the cylinder
improve the engine's exhaust scavenging capability, and hence increase its power output
allow the use of high octane fuel
The type of fuel used in a turbocharged engine would be:
AVTUR
AVGAS
AVTAG
AVPIN
At an idle or low power condition, the turbocharger wastegate is normally:
partially open
fully open
closed
half open
When the air or the mixture passes through the diffuser shroud, the energy conversion is from:
kinetic to pressure
heat to potential
mechanical to heat
potential to kinetic
The construction of a turbocharger ensures that the turbine and the compressor:
are on the same shaft
are on different shafts
are connected by mechanical gearing
are controlled by the ABC
The wastegate fitted to a turbocharger regulates the quantity of:
the mixture that enters the induction manifold
the atmosphere that can enter the compressor
the exhaust gas that will bypass the turbine
the exhaust gas that leaves the compressor
The main function of a supercharger is to:
increase the thermal efficiency of the engine
increase the compression ratio of the engine
maintain sea level pressure in the engine to above rated altitude
increase the volumetric efficiency of the engine
The response of a turbocharged engine to rapid throttle opening, when compared to a normally aspirated engine:
is initially better, but exhaust back pressure will cause a flat spot
is always better
is worse
is identical
