Question 40-1 : A csd unit is normally provided with means of monitoring during flight the ? [ Course pilot ]
Oil temperature and pressure
Question 40-2 : The phase relationship between two unparalleled ac generators ?
Is unimportant
Question 40-3 : Assuming a csd fault is indicated the csd should be disconnected ?
Provided the engine is running
The function of a constant speed drive csd is to ensure that the ac generator produces a constant frequency in case of csd fault you must disconnect it if the engine is running if not since the ac generator is not rotating you don't need to disconnect it .a csd unit which has been disconnected may be reset on the ground only after engine shut down
Question 40-4 : Ac generators operated in parallel must have the same ?
Voltage and phase
Two ac generators operated in parallel must be not only at the same speed voltage but also the same phase to be paralleled
Question 40-5 : The measured output power components of a constant frequency ac system are ?
Kva and kvar
Question 40-6 : 'frequency wild' in relation to a ac generation system means the generator ?
Output frequency varies with engine speed
Question 40-7 : When the ac voltage across a capacitor is kept constant and the frequency is increased the current through the capacitor will ?
Increase
Capacitive reactance .when frequency tends to zero current magnitude is almost equal to zero .at contrary when fequency is high this is the magnitude of the voltage which tends to zero . 876.we are talking about capacitive reactance xc expresses in ohm
Question 40-8 : In an aeroplane fitted with a constant frequency ac power supply dc power is obtained from a ?
Transformer rectifier unit tru
Question 40-9 : On an aeroplane using ac as primary power supply the batteries are charged in flight from ?
A transformer rectifier unit
Question 40-10 : Immediately after starting engine s with no other electrical services switched on an ammeter showing a high charge rate to the battery ?
Would be normal and is only cause for concern if the high charge rate persists
If the engine was started electrically using the battery there would have been a significant drain on the battery .the ammeter shows a charge after start up to replenish the energy just drained from the battery
Question 40-11 : Circuit breakers protecting circuits may be ?
Used in ac and dc circuits
Question 40-12 : The function of a csd in an ac generating system is to ?
Drive the generator at a constant speed
Question 40-13 : Because of the input/output relationship of an and gate it is often referred to as the ?
'all or nothing' gate
Question 40-14 : The function of a not logic gate within a circuit is to ?
Invert the input signal such that the output is always of the opposite state
Question 40-15 : When two dc generators are operating in parallel control of load sharing is achieved by ?
An equalising circuit which in conjunction with the voltage regulators varies the field excitation current of the generators
Question 40-16 : A condenser in parallel with breaker points will ?
Intensify current in secondary winding
This question is about the ignition on a piston engine and the use of a magneto .the components of a typical magneto consist of . a permanent magnet . a primary and a secondary windings on a core . a way of making the magnet or the core move by rotating either one . contact breaker points . a condenser capacitor . a distributor .inside the primary circuit is a set of conctact points that make the flux reversals more abrupt when they open and close at critical moments .the condenser capacitor is mainly there to absorb the sparks and reduce arcing to stop the points getting pitted and worn it is connected across the contact points so it is shorted out when they close but the instant they open it absorbs the current from the collapsing current in the primary coil i e it is charged so the points open cleanly with very few sparks this is know as a spark quench the current from the capacitor when it discharges also hastens the collapse of the primary field by opposing it to increase the induced voltage .the more sudden the breaking of the primary circuit is the more current will be induced in the secondary coil
Question 40-17 : A unit that converts electrical dc into ac is ?
An inverter
Dc to ac inverter .ac to dc rectifier
Question 40-18 : On board electrical systems are protected against faults of the following type .1 ac generator over voltage.2 ac generator under voltage.3 over current.4 csd or generator over speed.5 under frequency.6 undue vibration of ac generators.the combination of correct statements is ?
1 2 3 4 5
The on board electrical systems are protected for all of these scenarios except for vibration of the generator
Question 40-19 : The purpose of a battery control unit is generally to isolate the battery .1 from the bus when the battery charge has been completed.2 when there is a battery overheat condition.3 in case of an internal short circuit.4 in case of a fault on the ground power unit.the combination which regroups ?
1 2 and 3
Question 40-20 : The resistors r1 and r2 are connected in parallel the value of the equivalent resistance req so obtained is given by the following formula ?
1/req = 1/r1 + 1/r2
Question 40-21 : The function of the generator breaker is to close when the voltage of the ?
Generator is greater than battery voltage and to open when the opposite is true
The generator breaker is controlled by sensors that detect over/under speed over/under frequency reverse or over current plus the control for bringing the generator on or offline .the function of the generator breaker is to close when the voltage of the generator is greater than battery voltage and to open when the opposite is true
Question 40-22 : The input and output of a static inverter are respectively ?
Dc and ac
Question 40-23 : Alternating current can be derived from direct current by ?
An inverter
Question 40-24 : The rating of electrical fuses is expressed in ?
Amperes
Question 40-25 : A 'zener' diode is used for ?
Voltage stabilisation
A zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode but will also permit it to flow in the reverse direction when the voltage is above a certain value but keeps it constant .the zener diode is used for voltage stabilisation
Question 40-26 : The type of gate which requires all conditions with logic 1 for engagement is ?
And
A logic gate is an elementary building block of a digital circuit most logic gates have two inputs and one output at any given moment every terminal is in one of the two binary conditions low 0 or high 1 represented by different voltage levels the logic state of a terminal can and generally does change often as the circuit processes data .there are seven basic logic gates and or xor not nand nor and xnor .the and gate is so named because if 0 is called 'false' and 1 is called 'true' the gate acts in the same way as the logical 'and' operator the following illustration and table show the circuit symbol and logic combinations for an and gate in the symbol the input terminals are at left and the output terminal is at right the output is 'true' when both inputs are 'true' otherwise the output is 'false'
Question 40-27 : To reverse the direction of rotation of a shunt type parallel field dc electric motor it is necessary to ?
Reverse the polarity of either the stator or the rotor
Changing the polarity of the current would change the direction of the field around the conductor whilst leaving the polarity of the main field unchanged
Question 40-28 : The power required for field excitation of the main rotor in modern constant frequency alternators is directly controlled by ?
The voltage regulator
When a brushless generator's rotor is initially driven by the csd unit a permanent magnet generator induces an ac voltage into the pilot output the ac voltage is then full wave rectified and fed to the main exciter by way of the voltage regulator the three phase winding on the rotor now has a voltage induced in it which is fed to the dc main field by way of a three phase rectifier network . the dc main field rotates and induces a voltage in the ac output windings which at the same time increases the output of the pilot exciter . this sequence of events continues until the generator reaches its regulated output voltage the output is typically 200/115 volts three phase 400 hz
Question 40-29 : The ignition system generally used for small aircrafts is a ?
High tension system
.the sole purpose of the ignition system is to supply a high energy spark at the right moment thereby igniting the fuel air mixture so that the engine can start its power stroke .the source for the spark comes from the magnetos .in the magneto the magnetic field generates a voltage in the coil which is transformed to a higher voltage by a secondary coil with much more windings than the primary coil a breaker contact in the primary coil circuit interrupts the flowing current and this interruption causes the magnetic field to collapse thereby generating a very high peak voltage in the secondary coil this peak voltage is then conducted to the correct spark plugs by the distributor and high voltage leads
Question 40-30 : Because of the connection in parallel of electrical equipments on an ac bus bar isolation of individual equipments ?
Decreases the bus bar current consumption
In parallel ac current is shared between the different electrical equipments connected on the bus bar .if you disconnect one of them bus bar current consumption will be reduced
Question 40-31 : Regarding 1 a fuse and 2 a circuit breaker ?
1 is not resettable 2 is resettable
Question 40-32 : Regarding ohm's law ?
The current in a circuit is directly proportional to voltage
Question 40-33 : When the ac generators are connected in parallel the reactive loads are balanced by means of the ?
Excitation current
If generators are to be paralleled frequency is adjusted by adjusting csd output torque to balance the real load and the reactive loads are trimmed by adjusting the excitation current from the voltage regulator
Question 40-34 : Generators when connected to the same bus bar are usually connected ?
In parallel mode
Question 40-35 : The advantages of nickel cadmium compared with lead acid batteries are .1 lower risk of thermal runaway.2 higher internal resistance hence higher power.3 reduced charging time.4 constant output voltage.the combination which regroups all the correct statements is ?
3 4
Question 40-36 : Static dischargers .1 are used to set all the parts of the airframe to the same electrical potential .2 are placed on wing and tail tips to facilitate electrical discharge .3 are used to reset the electrostatic potential of the aircraft to a value approximating 0 volts .4 are located on wing ?
2 4 5
We are not looking to set all the parts of the airframe to the same electrical potential we are looking to maintain the electrical airframe potential at around 10000 volts via the static dischargers by providing a path for the electrons .example of static dischargers on a wing . 810..without static dischargers the electrical airframe potential would rise up to a value 10 times higher and would disturb and/or damage the onboard equipment
Question 40-37 : Assuming the initiating cause is removed which of these statements about resetting are correct or incorrect .i a fuse is resettable .ii a circuit breaker is resettable ?
I is incorrect ii is correct
Question 40-38 : Assuming the initiating cause is removed which of these statements about resetting are correct or incorrect .i a fuse is not resettable .ii a circuit breaker is resettable ?
I is correct ii is correct
Question 40-39 : The diagram shown in annex represents a twin engine aeroplane electrical system batteries are located at positions . 877 ?
1 and 2
Img878.each generator has its own busbar with non essential services connected to it or those that don't matter if it fails both are ultimately connected in parallel to a central combining busbar which carries the essential services batteries are located on the hot bus 1 and hot bus 2 providing a source of power if both generators fail
Question 40-40 : Electrical work measurement unit in the international system of units si is ?
Joule
Unit of force the unit of force in the mks metre kilogram second system is the force which gives to a mass of 1 kilogram an acceleration of 1 metre per second per second . joule unit of energy or work the joule is the work done when the point of application of 1 mks unit of force newton moves a distance of 1 metre in the direction of the force . watt unit of power the watt is the power which in one second gives rise to energy of 1 joule . ampere unit of electric current the ampere is that constant current which if maintained in two straight parallel conductors of infinite length of negligible circular cross section and placed 1 metre apart in vacuum would produce between these conductors a force equal to 2 x 10&8722 7 mks unit of force newton per metre of length . ohm unit of electric resistance the ohm is the electric resistance between two points of a conductor when a constant potential difference of 1 volt applied to these points .produces in the conductor a current of 1 ampere the conductor not being the seat of any electromotive force
Request for information. If you have any questions about our practice MCQs, our mock exams or if you would like additional information about our educational tool, do not hesitate to ask us. We are available to guide you during your preparation journey.
Exclusive rights reserved. Reproduction prohibited under penalty of prosecution.
