Superchargers + Electrical + Ignition Systems

Question 1

During take-off in an aircraft with a turbocharged engine,
[a] full power must be achieved before the brakes are released
[b] throttles should be opened fully initially then reduced to rated boost
[c] throttles should be opened smoothly and care taken not to exceed rated boost
[d] maximum continuous power should not be exceeded

Answer 1

C
Turbo charged engines are much more prone to overboosting.

Question 2

Dual ignition on an aircraft engine provides an additional safety factor during flight. It is also necessary to
provide
[a] extra power from hotter combustion temperature
[b] efficient combustion of the charge during the power stroke
[c] longer combustion time and therefore more power
[d] easier burning of the charge when the mixture is rich

Answer 2

B
Two flame fronts are required to allow the large charge to burn in the time available.

Question 3

An aircraft electrical system operates at approximately constant
[a] voltage
[b] ampage
[c] power
[d] resistance

Answer 3

A
Volts remain constant, while amps vary according to demand.

Question 4

If an aircraft with a flat battery is hand started
[a] the alternator may be damaged
[b] the alternator may remain off line after the engine has started
[c] the alternator must not be turned on after the engine has started
[d] the alternator may over charge the battery

Answer 4

B
The alternator requires a small charge from the battery to excite the magnetic field.

Question 5

If an alternator failure occurs during flight, the indications to the pilot would be
[a] a discharge showing on a left hand zero ammeter
[b] zero showing on a centre zero ammeter
[c] an unusually high charge rate showing on a left hand zero ammeter
[d] a discharge showing on a centre zero ammeter

Answer 5

D
The battery begins to supply the system demands. The ammeter shows discharge.

Question 6

If the electrical load is so high that the alternator cannot supply the demands of the system the indications on a
centre zero ammeter would be
[a] warning light on and charge showing
[b] warning light on and discharge showing
[c] warning light off and charge showing
[d] warning light off and discharge showing

Answer 6

D
The battery begins to export power to assist the alternator. Since the alternator has not
failed, the warning light remains off.

Question 7

Circuit breakers and fuses protect an electrical circuit from
[a] too many volts
[b] too many amps
[c] reversing of the current flow
[d] being left on too long

Answer 7

B
Circuit breakers and fuses are rated in amps. ie ‘a 10 amp fuse’. This indicates the
number of amps it can tolerate before breaking the circuit.

Question 8

A micro switch is
[a] a very very small switch
[b] a remote switch activated from the cockpit
[c] a remotely located switch which cannot be directly activated from the cockpit
[d] a switch in a circuit with a very small current

Answer 8

C
Micro switches are found on flaps and undercarriages. They automatically switch off
the circuit when extension or retraction is complete. The pilot has no control over its
operation.

Question 9

Solenoids allow a heavy circuit to be turned on or off by the use of
[a] a strong spring
[b] high voltage from the battery
[c] hydraulic pressure
[d] a lighter current to an electromagnet

Answer 9

D
Solenoids avoid the need for heavy, high tension leads to be brought into the cockpit.

Question 10

The capacity of a battery is measured in
[a] amp hours
[b] amps
[c] volts
[d] volt hours

Answer 10

A
A 24 amp hour battery, when fully charged, can supply any combination of amps and
hours that multiply to make 24 ie 6 amps for 4 hours or 3 amps for 8 hours etc.

Question 11

Vents are required in a battery compartment to ensure that
[a] water and dirt are kept out of the vicinity of the battery
[b] battery acid can drain out of the compartment during charging
[c] gas pressure cannot build up in the battery compartment
[d] dangerous gases such as hydrogen do not accumulate near the battery during charging

Answer 11

D
Hydrogen and oxygen are generated during recharging.

Question 12

If a magneto earth lead becomes disconnected or breaks
[a] that magneto cannot be turned off
[b] that magneto will not provide any spark
[c] the engine will “dead cut” when that magneto is selected
[d] that magneto will provide intermittent spark

Answer 12

A
A magneto is switched off by completing the circuit to earth. If the circuit is broken,
the magneto will remain ‘live’.

Question 13

The purpose of an impulse coupling on a magneto is to-
[a] guard against the magneto being turned off accidentally
[b] produce a strong and retarded spark while the engine is being cranked
[c] ensure a strong spark is available during high power operation
[d] obtain an electrical current from the alternator if the magneto fails

Answer 13

B
The impulse is provided to assist the magneto to produce a spark when the engine is
not spinning fast. It also changes the timing to make starting easier.

Question 14

The purpose of a supercharger or turbocharger is to-
[a] to supply extra fuel to the engine when it is operating at high power
[b] to increase the density of the air in the induction system
[c] to ensure that detonation does not occur at high power settings
[d] to distribute fuel evenly to each cylinder

Answer 14

B
Superchargers and turbochargers increase the mass air flow to the engine. The extra
air allows extra fuel to be added to produce extra power.

Question 15

The pilot of a turbocharged aircraft notices that the manifold pressure indication shows abnormal fluctuations
during a long climb. Select the most likely cause-
[a] detonation is occurring in one of the cylinders
[b] there is a leak in the exhaust system
[c] the wastegate is sticking
[d] there is a leak in the induction system

Answer 15

C
The wastegate can ‘coke up’ with exhaust by-products and become sticky. This
produces erratic manifold pressure fluctuations during climb as the wastegate sticks
and ‘lets go’ in jerky movements.

Question 16

A leak in the induction system of a turbocharged engine with automatic boost control will be most noticeable-
[a] during taxi
[b] at take-off
[c] during cruise at low level
[d] on a climb to high level

Answer 16

D
A leak is more noticeable at high level because more air is lost due to the increased
pressure gradient between the reduced outside atmospheric pressure and the constant
upper deck pressure.

Question 17

A turbocharged engine with automatic boost control is operating below the critical altitude. A leak developing
upstream of the turbine in the exhaust system will result in-
[a] abnormal fluctuations in the manifold pressure indication
[b] the wasegate moving towards the closed position
[c] the wasegate moving towards the open position
[d] a sudden drop of manifold pressure.

Answer 17

B
Any exhaust gas that escapes through the leak does not pass through the turbine. The
turbine and compressor RPM try to drop, but the automatic system closes the waste
gate to send extra gas through the turbine to compensate for the leak.

Question 18

Prior to an alternator failure in flight the left-hand zero ammeter was reading 12 amps. If no electrical loads
were turned off, a 20 amp/hour battery could supply the system for approximately-
[a] 30 minutes
[b] 60 minutes
[c] 90 minutes
[d] 100 minutes

Answer 18

D
A 20 amp/hour battery can supply any combination of amps and hours that multiply to
make 20. If the system was using 12 amps the battery would last 20 ÷ 12 = 1.7 hours
which is approximately 100 minutes. Note we are ignoring the small portion of the 12
amps which would have been going to the battery before the alternator failure.

Question 19

An aircraft is equipped with a voltmeter. Before start-up with the master switch on, the voltmeter reads 24 volts.
The reading that would indicate normal operation during cruise would be -
[a] 24 volts.
[b] less than 24 volts.
[c] 28 volts.
[d] varying depending on the load on the system.

Answer 19

C
The voltmeter simply reads the system voltage at all times. In a 24 volt system it will
read the battery’s voltage [24] before start-up. During cruise it will read the voltage
output of the alternator. In a 24 volt system, the alternator’s output will be set slightly
highter than the battery, 28 volts. It will not vary with electrical loads - only a lefthand
ammeter will do that.

Question 20

Given the following data.
Item Operating current [amps]

VHF Com. 2
VHF Nav. 2
GPS. 4
ADF. 2
Transponder. 4
Navigation Lights. 8
Instrument Lights. 3
Strobes. 5
Rotating Beacon. 5

After an in-flight failure of the alternator, the pilot of the above aircraft turns off all items of electrical equipment
except for the VHF Com, Transponder and GPS. If the battery has a capacity of 20 amp/hours and was fully
charged at the time of the failure, the approximate time for which it could be expected to supply the system
demands is -
[a] 150 minutes. [b] 120 minutes.
[c] 200 minutes. [d] 60 minutes.

Answer 20

B
The load on the system with those items on would be 2 + 4 + 4 = 10 amps. A 20 amp/
hour battery could supply this load for 20 ÷ 10 = 2.0 hours = 120 minutes.

Question 21

The function of a rectifier in an electrical system is to -
[a] convert AC current to DC current
[b] allow the current to flow in only one direction.
[c] convert DC current to AC current.
[d] maintain a constant system voltage.

Answer 21

A
A rectifier converts AC current to DC current.

Question 22

The function of a inverter in an electrical system is to -
[a] convert AC current to DC current
[b] allow the current to flow in only one direction.
[c] convert DC current to AC current.
[d] maintain a constant system voltage.

Answer 22

C
An inverter converts DC current to AC current.

Question 23

Your aircraft is equipped with a voltmeter and you note that before start-up with the master switch on, the
instrument reads 24 volts. After an alternator failure in flight, this instrument would be expected to read:
[a] zero
[b] more than volts
[c] less than 24 volts
[d] 24 volts

Answer 23

D
A voltmeter always reads the system voltage. Because the alternator is always set to
produce a voltage a little higher than the battery, you would expect the voltmeter to
read more than 24 volts during normal operation. However should the alternator fail
during flight, the battery will supply the system voltage. The voltmeter will then read
the battery’s voltage - which in this case is 24 volts.

Question 24

The primary purpose of circuit breakers as used in aircraft electrical systems is to
[a] provide a means of breaking the circuit manually in flight in case of emergency
[b] prevent the development of open circuits with the possibility of fire
[c] regulate the voltage applied to various units
[d] protect electrical units from overloading and reduce the fire hazard from short circuits

Answer 24

D
Circuit breakers react to the amount of current [amps] flowing in the circuit rather
than the voltage which remains nearly constant. If too much current flows the circuit
overheats causing either damage to the equipment or fire - or both.

Question 25

It is advisable to check magnetos at pre-flight to make sure both are operating and capable of being shut off. This check should be made
[a] during engine run-up, before takeoff
[b] at idle speed, as soon as the engine is running smoothly after start-up
[c] at a throttle setting equivalent to cruising speed
[d] at full throttle

Answer 25

A
Magneto checks are a necessary item in the pre-takeoff checks

Question 26

An impulse magneto coupling
[a] reduces magneto speed during engine warm up
[b] advances ignition timing and gives a hotter spark at starting
[c] retards ignition timing and gives a hotter spark at starting
[d] gives an automatic spark increase during high speed operation

Answer 26

C
The impulse causes the magneto to flick quickly at an exact time during engine
cranking. This produces a strong spark later than normal [retarded] in the cycle. The
retarded spark is necessary because of the very slow rotational speed during engine
cranking.

Question 27

In the event of a failure of the generator or alternator of an aircraft’s electrical system there will be an ammeter
indication and
[a] a high current discharge from battery to generator or alternator
[b] a deterioration of all electrical services including ignition
[c] a high discharge showing on a left-hand zero ammeter
[d] no obvious change in electrical services

Answer 27

D
When the alternator fails the battery becomes the only voltage source. The system
simply switches to feed off the battery and the pilot would know nothing of it without
an ammeter or warning light to alert him/her to the failure.

Question 28

A pilot should avoid prolonged operation of an electric starter motor as this can cause
[a] damage to the gears on the crankshaft and starter motor
[b] boiling of the electrolyte in the battery
[c] weakening of the bendix spring
[d] overheating of the starter motor

Answer 28

D
Unlike other electric motors, starter motors are not intended for prolonged use. They
drain a very great amount of current and quickly become overheated if engaged for
continuous periods. Usually no more than 10 seconds is recommended.

Question 29

The magneto ground wire is connected to
[a] the nearest steel part of
the engine or mounting
[b] the distributor head
[c] the magneto switch
[d] the case of the magneto

Answer 29

C
The magneto is turned off or on by making or breaking the circuit to earth [ground].

Question 30

A dual ignition system on light aircraft engines
[a] provides added safety
[b] produces a stronger spark for easier starting and provides added safety
[c] provides added safety and produces more efficient combustion
[d] produces more efficient combustion

Answer 30

C
Dual ignition is not only used for safety. Because of the size of aircraft cylinders, two
sparks are necessary to ensure the charge can be burnt in the time available.

Question 31

With the majority of opposed engines, the right-hand magneto
[a] fires the left top and the right bottom plugs
[b] fires the right top and left bottom plugs
[c] fires the left top spark plug first
[d] fires both plugs immediately

Answer 31

A
The right magneto fires the bottom plugs on the right hand side and the top plugs on
the left hand side. The left magneto fires the remainder.

Question 32

The generator fails just after take-off in an aircraft which has a 48 amp-hour, 24 volt battery. Just prior to failure,
the centre index ammeter was reading a charge of 5 amps. Without switching off any loads, the approximate
maximum interval before the battery goes flat
[a] could not be accurately determined
[b] would be about 4 hours 48 minutes
[c] would be about 9 hours 36 minutes
[d] would be about 2 hours

Answer 32

A
A centre zero ammeter indicates the current flowing to [or from] the battery. During
normal operation it tells you nothing about the drain going to the other electrical loads.
The fact that it read 5 amps before the alternator failure would tell you nothing about
how long the battery will last. After the failure however, it would indicate the current
flowing from the battery to the system. That figure would be an indication of the time
the battery will last.

Question 33

An impulse coupling on a magneto
[a] may cause pre-ignition if it is too ‘hot’ for the engine in which it is fitted
[b] produces easier stopping of the engine
[c] can be either a high-tension or a low-tension type
[d] produces a ‘hot’ spark for easier starting by momentarily increasing the rotational speed of the
magneto

Answer 33

D
The impulse holds the magneto shaft still while a strong spring is wound up tight.
When it releases, it flicks very quickly to produced a strong spark.

Question 34

On a 4-stroke engine, the ignition is timed so that the spark occurs
[a] after TDC on the power stroke
[b] before TDC on the compression stroke
[c] after TDC on the compression stroke
[d] before TDC on the power stroke

Answer 34

B
The spark occurs just before TDC to allow the burn to be completed at the maximum
torque position on the power stroke.

Question 35

When one magneto is switched OFF in a dual ignition system
[a] engine power is reduced because the increased c
ombustion time results in a lower peak
combustion pressure later in the power stroke
[b] the peak combustion pressure is reduced
[c] the ignition timing will be ‘retarded’, i.e. peak pressure will occur late in the power stroke
[d] engine power is increased

Answer 35

A
When only one flame front has to burn the charge it takes longer to complete the burn.
Since the magneto fires at the normal time, the burn is not completed until later in the
power stroke - this misses the point of maximum torque so power is lost.

Question 36

If an engine is allowed to operate too long at idling speed
[a] the spark plugs may become fouled
[b] the piston rings may show excessive wear
[c] the spark plugs will become inoperative
[d] the piston head may warp

Answer 36

A
The oil tends to pool in the bottom of the cylinders [for horizontally opposed engines].
At low power the combustion chamber is not hot enough to burn all of the oil so oil
fouls the bottom plugs causing misfire.

Question 37

A condenser is incorporated in the primary circuit of a magneto to
[a] prevent burning of the points
[b] prevent damage to the armature of the rotating magnet
[c] prevent sudden collapse of the primary circuit
[d] permit the current to jump the points at the correct instant

Answer 37

A
Without a condenser when the breaker points open to break the circuit the current
would jump the gap as a spark and this would cause burning of the points. The con
denser stores the current momentarily so that it doesn’t keep flowing across the points
as a spark.

Question 38

Shielding, as employed in aircraft electrical systems, is used for
[a] preventing leakage of high voltage
[b] reducing noise in radio receiving and transmitting equipment
[c] protecting the pilot from injury by electrical shock
[d] providing a return ground path for rubber shock mounted equipment

Answer 38

B
The high voltage current flowing in pulses to the spark plugs generates radio waves.
Without shielding, the radio waves would cause interference [static] in the aircraft
radios.

Question 39

A reading of zero on a centre zero ammeter indicates
[a] the alternator’s voltage has dropped to equal that of the battery
[b] alternator failed
[c] battery fully charged
[d] battery flat

Answer 39

A
A zero reading on a centre zero ammeter means that there is no current flowing to or
from the battery. This means that the load is equal to the generator/alternator maxi
mum output. This is not normal - there should always be some current going to the
battery.

Question 40

A voltage regulator controls alternator output by
[a] shorting out the field in the event of overload
[b] stopping rotation of the alternator when the circuit is overloaded
[c] introducing a resistance in the alternator lead to the battery in the event of an overload
[d] varying the current flow to the alternator field coil

Answer 40

D
A zero reading on a centre zero ammeter means that there is no current flowing to or
from the battery. This means that the load is equal to the generator/alternator maxi
mum output. This is not normal - there should always be some current going to the
battery.

Question 41

An aircraft fitted with a voltmeter which reads 24 volts prior to start. During cruise, normal operation of the
electrical system would be indicated with the voltmeter showing
[a] 0 volts
[b] less than 24 volts
[c] 24 volts
[d] 24-28 volts

Answer 41

D
The voltage regulator makes the alternator field stronger or weaker according to the
system demands.

Question 42

During flight the center zero ammeter in an aircraft is deflected to the left of centre [a slight discharge]. This indicates
[a] the battery is fully charged and the alternator is charging the battery
[b] the electrical load matches the alternator output
[c] the demand of the electrical system is greater than the alternator output
[d] the electrical load is less than the alternator output

Answer 42

C
If the centre zero ammeter indicates negative [discharge], the battery voltage must be
higher than the alternator. There are too many loads on or the alternator has failed.

Question 43

If a left-hand-zero ammeter indicates zero during flight
[a] the alternator has failed
[b] all electrical loads are on
[c] the battery is fully charged
[d] the battery circuit is switched off

Answer 43

A
The left hand zero ammeter simply indicates the total output of the alternator.

Question 44

If the take-off manifold pressure exceeds rated boost in a turbo-charged engine
[a] fuel vaporisation will occur
[b] detonation and engine damage could result
[c] the engine will back-fire and lose power
[d] cylinder head temperatures will become too low and power
will be less than normal

Answer 44

B
The more a gas is squeezed the hotter it becomes. If the manifold pressure is above
the rated boost for the engine, the gas will become too hot during the compression
stroke - when the spark occurs it detonates.

Question 45

A left-hand-zero ammeter shows a constant high output when
[a] the alternator has failed
[b] the alternator voltage is low
[c] all electrical loads are on
[d] the battery is fully charged

Answer 45

C
A left hand zero ammeter shows the total output of the alternator. Each time you turn
on a new piece of equipment the alternator output has to increase to cope. When all
electrical loads are on, the left hand zero ammeter will be at its maximum reading

Question 46

In a turbo charged engine, with an increase in throttle after starting with the waste gate jammed shut, manifold
pressure will
[a] increase slower than normal
[b] increase at the normal rate
[c] increase faster than normal rate
[d] not increase above existing static pressure

Answer 46

C
If the waste gate is jammed shut, all of the exhaust gas is passing through the turbine.
When the throttle is opened there will be a rapid increase in manifold pressure.

Question 47

In an engine fitted with an automatic waste gate, oil pressure is used to
[a] open the wastegate in order to direct more air through the turbine
[b] close the wastegate in order to direct more air through the turbine
[c] open the wastegate in order to allow less air to bypass the turbine
[d] close the wastegate in order to allow more air to bypass the turbine

Answer 47

B
An automatic waste gate is spring loaded to the open position. The engine oil pressure
is used to push it towards the closed position - this sends more gas through the turbine
increasing the compressor speed.

Question 48

A turbocharged piston engine aircraft fitted with a manual [pilot operated] wastegate is climbing at full throttle
with the wastegate partially open. The correct action to maintain a constant Manifold Pressure as long as possible
on climb to the cruise altitude would be
[a] slowly decrease engine RPM as the climb progresses
[c] slowly richen the mixture as the climb progresses
[c] slowly open the waste gate as the climb progresses
[d] slowly close the waste gate as the climb progresses

Answer 48

D
As height increases the ambient atmospheric pressure drops. To compensate for this
the compressor has to work harder. As the waste gate is closed less gas is wasted and
more is sent to spin the turbine. This is necessary to maintain a constant manifold
pressure during climb.

Question 49

A turbocharged aircraft fitted with an automatic waste gate controlled by engine oil pressure which suffers a
failure cutting oil pressure to the waste gate control. The effect on engine operation is
[a] complete engine failure
[b] the engine will experience surging
[c] engine power will be reduced
[d] the engine will experience an overboost situation

Answer 49

C
An automatic waste gate is spring loaded to the open position. The engine oil pressure
is used to push it towards the closed position - if oil pressure fails the waste gate will
mover in favour of the spring i.e. towards the open position. More gas will be wasted
and less will go to dive the turbine. Manifold pressure [therefore power] will drop.

Question 50

When conducting a magneto check during run-up in an aircraft with separate switches for each magneto, there
is no change in RPM when the right magneto is switched off then on again and the engine fails when the left
magneto is switched off. A fault which would cause this is
[a] the left magneto has failed
[b] the right magneto has failed
[c] the left magneto is live
[d] the right magneto is live

Answer 50

B
With this arrangement of magneto switches each magneto has its own individual on-off
switch. Obviously if the engine fails when the left magneto is switched off, it must
have been running on only the left magneto all the while. The right magneto must
have failed.

Question 51

An unexpectedly high MP resulting from throttle advance in a turbo charged engine is most likely due to
[a] a waste gate sticking closed
[b] a waste gate sticking open or closed
[c] a waste gate sticking open
[d] too low an oil pressure acting on the piston in the waste gate actuator

Answer 51

A
If the waste gate is stuck in the closed position all of the gases will be directed to flow
through the turbine. This will drive the compressor at full speed and cause a dramatic
increase in upper deck pressure. Any movement of the throttle will produce a higher
than usual manifold pressure.

Question 52

Lead acid type batteries need to be located in a vented battery box within an aircraft
[a] so that internal pressures within the battery can be relieved at high operating altitudes
[b] to allow water to drain away from battery compartment
[c] so that airflow directed across the battery keeps its cool
[d] to dissipate the flammable gases produced as by-products of the chemical reaction occurring
within the battery

Answer 52

D
When a lead-acid battery is being charged, gases such as hydrogen are released. This
would be dangerous if the gas was allowed to build up in the battery compartment.

Question 53

The prime purpose of a turbo charger is to
[a] to increase the range of available RPM
[b] to lower engine fuel consumption
[c] to increase the mass air flow of an engine by increasing volumetric efficiency
[d] to reduce exhaust back pressure and increase the power at altitudes above MSL

Answer 53

C
The turbo charger pumps more air into the cylinders than would otherwise be possible.
This allows more fuel to be burnt and so produces more power.

Question 54

An aircraft is equipped with a conventional centre zero type ammeter. Such an ammeter displays
[a] current flow to and from the battery
[b] zero or a slightly negative reading during normal operations
[c] alternator output
[d] an increasing positive reading if more and more electrical services are switched
on in flight

Answer 54

A
A centre zero ammeter is situated in the battery circuit between the battery and the bus
bar. It indicates only the current flowing to or from the battery.

Question 55

A correct interpretation of a centre zero ammeter is that a
[a] positive deflection shows that the battery is supplying the current
[b] zero deflection indicates a generator fault
[c] negative deflection shows that the generator is charging the battery
[d] negative deflection shows that the battery is supplying the current

Answer 55

D
A positive deflection indicates that current is flowing to the battery - this is normal. A
negative deflection indicates that the battery is exporting power to the system - this is
not normal and would indicate a problem with the alternator.

Question 56

Battery compartment must be properly vented primarily in order to
[a] allow fluid seepage during rapid charging
[b] provide adequate cooling
[c] dissipate flammable gases
[d] prevent the battery from boiling

Answer 56

C
Gases such as hydrogen must be vented from the battery compartment.

Question 57

The purpose of a turbo charger is to
[a] increase the mass airflow to the engine
[b] increase the temperature and vaporisation of the fuel air change
[c] provide a constant rate of climb up to the critical altitude
[d] decrease the possibility of detonation

Answer 57

A
The turbocharger is really only an airpump that pumps extra air into the inlet manifold.

Question 58

During normal advancement of the throttle of a turbo charged engine, the MP rose excessively, this could have
been caused by
[a] an exhaust leak upstream of the waste gate
[b] an exhaust leak down stream of the waste gate
[c] the waste gate being jammed shut
[d] the waste gate being jammed open

Answer 58

C
If the waste gate is stuck in the closed position all of the gases will be directed to flow
through the turbine. This will drive the compressor at full speed and cause a dramatic
increase in upper deck pressure. Any movement of the throttle will produce a higher
than usual manifold pressure.

Question 59

Throttle operation during take-off for an engine fitted with a supercharger, should be
[a] careful operating with attention not to exceed rated boost
[b] rapid movement to rated boost, then slowly to the full throttle position
[c] slow opening of the throttle to full travel
[d] rapid movement to the fully open position

Answer 59

A
Even with an automatic waste gate care should be taken to ensure that the rated boost
is not exceeded. This could happen if the waste gate was sticking shut.

Question 60

If a left-hand-zero ammeter indicates an unusually high charge rate during flight
[a] the electrical system is overloaded
[b] the indication would be normal if all electrical loads are turned on
[c] the battery is fully charged
[d] the alternator has failed

Answer 60

A
The left hand zero ammeter measures the total output of the alternator. A very high
reading indicates that an unusually high demand is being placed on the alternator. It
could be too many loads are turned on or the battery is not accepting its charge.

Question 61

A turbocharger develops an exhaust leak upstream of the waste gate while operating above the critical altitude.
The immediate result will be
[a] a decrease in power output [b] no effect
[c] overboosting of the engine [d] power surges

Answer 61

A
A leak upstream of the waste gate [i.e. before the wastegate] means less gas is avail
able to run the turbine. Power will decrease.

Question 62

The altitude up to which a tubocharged engine can maintain rated boost manifold pressure is
[a] 10,000 feet [b] known as full throttle height
[c] known as the critical altitude [d] known as the critical height

Answer 62

C
Critical Altitude is the altitude at which, with the waste gate fully closed, the engine
can just produce rated boost when the throttle is fully open. The aircraft can climb
much higher than that - it is simply the height beyond which maximum rated power is
no longer available.

Question 63

The purpose of a waste gate is to
[a] direct exhaust gases to the inlet impeller
[b] release excess inlet manifold pressure to the atmosphere
[c] direct exhaust gases through the turbine to increase manifold pressure
[d] maintain atmospheric pressure in the inlet manifold

Answer 63

C
The waste gate decides how much gas is going to drive the turbine and how much is
allowed to escape directly to the outside atmosphere.

Question 64

During a ground magneto check you notice that there is no RPM drop when the switches are selected from
‘BOTH’ to ‘LEFT’. However when the selection from ‘BOTH’ to ‘RIGHT’ is made, a normal RPM drop is observed. A likely cause would be
[a] the left magneto is in excellent condition
[b] there is a fault in the right magneto earthing system
[c] there is a fault in the left magneto earthing system
[d] the left magneto spark plugs need replacing

Answer 64

B
When the left magneto is selected the right magneto should be turned off by sending
its primary current to earth. If no RPM drop occurs when the left magneto is selected
there is a fault in the earthing system of the right magneto.

Question 65

For an aircraft with individual magneto switches, no RPM drop is observed when the right magneto is turned off.
This most likely indicates
[a] the left magneto has failed completely
[b] the right magneto has failed completely
[c] the left magneto is producing an unusually strong spark
[d] both magnetos are functioning normally

Answer 65

B
If turning off the right magneto has no effect, it is safe to assume that it never was
working in the first place.

Question 66

During take off in an aircraft with a turbocharged engine,
[a] full power must be achieved before the brakes are released
[b] throttles should be opened fully initially then reduced to rated boost
[c] throttles should be opened smoothly and care taken not to exceed rated boost
[d] maximum continuous power should not be exceeded

Answer 66

C
A turbocharger pumps air into the inlet manifold via a compressor. The greatly
increased manifold pressure achieved with turbocharging can easily produce
overboosting on engines with no automatic control over manifold pressure.

Question 67

The centre zero ammeter is measured after the _____ which is _____ volts. The left hand zero ammeter is measured after the ______ which is _____ volts:

[A] alternator 24 volts. battery 28 volts
[B] battery 28 volts. alternator 24 volts
[C] alternator 28 volts. battery 24 volts
[D] battery 24 volts. alternator 28 volts.

Answer 67

D