A free Premium account on the FCL.055 website! Read here
Sign up to unlock all our services and 15164 corrected and explained questions.
Question 41-1 : If two constant frequency ac generators are operating independently, then the phase relation between both generators ? [ Regulation weather ]
Is unimportant.
Question 41-2 : The logic symbol shown represents assuming positive logic . 880 ?
An invert or not gate.
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...a logical inverter , sometimes called a not gate to differentiate it from other types of electronic inverter devices, has only one input. it reverses the logic state.. 881
Question 41-3 : The connection in parallel of two 12 volt/40 amp hours batteries, will create a unit with the following characteristics ?
12 volt/ 80 amp hours.
Battery packs achieve the desired operating voltage by connecting several cells in series, with each cell adding to the total terminal voltage.24 volt / 40 amp hours...parallel connection attains higher capacity for increased current handling, as each cell adds to the total current handling.12 volt/ 80 amp hours...in parallel we increase the flow, in series we increase tension.
Question 41-4 : The capacity of a battery is the ?
Amount of ampere hours that a fully charged battery can supply.
Question 41-5 : The frequency of the current provided by an alternator depends on ?
Its rotation speed.
Question 41-6 : Direct current generators are connected ?
In parallel to provide maximum power.
Generators run most efficiently when loaded to their rated capacity. therefore, when load demand increases, one or more generators can be connected in parallel to provide more power. this is the only way to reach maximum power with dc generators.
Question 41-7 : When carrying out a battery condition check using the aircraft's voltmeter ?
A load should be applied to the battery in order to give a better indication of condition.
Question 41-8 : When a battery is almost fully discharged there is a tendency for the ?
Voltage to decrease under load.
Question 41-9 : To ensure correct load sharing between ac generators operating in parallel ?
Both real and reactive loads must be matched.
Question 41-10 : The frequency of an ac generator is dependent on the ?
Number of pairs of poles and the speed of the moving part.
The frequency of the induced ac current depends on the revolution of the rotor. since rate of revolution is revolutions per minute rpm and frequency is expressed as cycles per second, the frequency of the induced ac current will be the rate of revolution of the rotor divided by 60...in addition to above, if two magnets are used two pole pairs the frequency is doubled tripled for three. thus putting all of this in a formula we get..frequency hz = rpm x number of pole pairs / 60.
Question 41-11 : If a current is passed through a conductor which is positioned in a magnetic field ?
A force will be exerted on the conductor.
When a current is passed through the wire wrapped around a conductor, its magnetic field penetrates the conductor, and causes the domains to turn, aligning parallel to the magnetic field, so their tiny magnetic fields add to the wire's field, creating a large magnetic field that extends into the space around the magnet... the larger the current passed through the wire coil, the more the domains align, and the stronger the magnetic field is.
Question 41-12 : The alternators, when connected, are usually connected ?
In parallel mode.
Question 41-13 : The capacity of an accumulator is ?
The quantity of electricity that the battery can supply during discharge.
.a battery's capacity is the quantity of electricity that it can supply during discharge. the more electrolyte and electrode material there is in the cell the greater the capacity of the cell..a small cell has less capacity than a larger cell with the same chemistry, and they develop the same open circuit voltage...because of the chemical reactions within the cells, the capacity of a battery depends on the discharge conditions such as the magnitude of the current which may vary with time , the allowable terminal voltage of the battery, temperature, and other factors. the available capacity of a battery depends upon the rate at which it is discharged. if a battery is discharged at a relatively high rate, the available capacity will be lower than expected.
Question 41-14 : The moving part in an ac generator is usually referred to as the ?
Rotor.
Question 41-15 : The purpose of bonding the metallic parts of an aircraft is to ?
Provide safe distribution of electrical charges and currents.
.the single earth return uses the aircraft structure as a return path. if the component is not electrical, it does not need a return path but still requires bonding to equalise potential difference in the event of static build up. this is why the answer provide a single earth for electrical devices is false.
Question 41-16 : A constant speed drive aims at ensuring ?
That the electric generator produces a constant frequency.
Question 41-17 : When a persistent underexcitation fault is detected on an ac generator connected to the aircraft mains with another ac generator, the protection device opens ?
The exciter control relay, the generator breaker and the tie breaker.
A control relay is a 'magnetic switch' which can isolate a circuit, so is in effect the same as a 'breaker'. an 'exciter breaker' and an 'exciter control relay' are in effect the same thing..an exciter breaker exciter control relay will isolate the power to the voltage regulator..the generator breaker will isolate the generator from the bus bar..the tie breaker will isolate two different bus bars from each other, or can connect two generators to the same bus bar..in most cases you will want to keep bus bars connected so that you can use all your services, so you will trip the generator breaker to isolate the generator from the bus bar, and the exciter breaker so you effectively shut down that generator..if you have 2 generators supplying the same single bus bar then you will trip the tie breaker to isolate generator and the generator and exciter breakers to isolate and shut down the generator.
Question 41-18 : A test to assess the state of charge of a lead acid battery would involve ?
Comparing the 'on load' and 'off load' battery voltages.
Question 41-19 : The advantages of grounding the negative pole of the aircraft structure are. 1 weight saving. 2 easy fault detection. 3 increase of short circuit risk. 4 reduction of short circuit risk. 5 circuits are not single wired lines. the combination regrouping all the correct statements is ?
1, 2, 4.
.the fuselage is used as an earth return for electrical components on an aircraft, which means that you only need one length of cable the battery will be connected by its negative pole. this saves weight and space, as you don't need two cables to complete a circuit..statement 3 increase of short circuit risk is not an advantage... and statement 5 circuits are not single wired lines is wrong..correct answer '1, 2, 4' is the most correct one, even if we are not totally agree with.
Question 41-20 : When an 'open circuit' occurs in an electrical supply system, the ?
Loss of continuity will prevent its working components from functioning.
.short circuit open circuit fault as the most common failure of aircraft electrical power supply system, when an 'open circuit' occurs the components connected on the circuit cease to operate.
Question 41-21 : An ac generator driven by a csd unit ?
Requires a voltage controller to maintain constant voltage under load.
The csd constant speed drive is a hydro mechanical unit fitted between the engine gearbox and the generator. its function is to maintain a constant generator speed regardless of engine speed... for a three phase generator to maintain 400hz this would be 8000 rpm. although generator speed remains constant, the electrical load will vary according to services selected. to maintain a steady output voltage the strength of the field excitation is controlled by the voltage regulator.
Question 41-22 : Consider the variable pitch propeller of a turbo prop. during deceleration ?
When braking, the propeller supplies negative thrust and absorbs engine power.
When braking , it means when you move the power lever in the reverse or beta range...in the 'reverse' pitch position, the engine/propeller turns in the same direction as in the normal forward pitch position, but the propeller blade angle is positioned to the other side of flat pitch. in reverse pitch, air is pushed away from the airplane rather than being drawn over it. reverse pitch results in braking action, rather than forward thrust of the airplane.
Question 41-23 : The correct formula to calculate the total displacement of a multi cylinder piston engine is the ?
Piston area x piston stroke x number of cylinders
Question 41-24 : When changing power on engines equipped with constant speed propeller, engine overload is avoided by ?
Increasing the rpm before increasing the manifold pressure.
A small trick.propeller´s control is the bravest.the first to enter increase the rpm, before increase the map and the last to leave decrease the map, before decrease the rpm.
Question 41-25 : The blade angle of a constant speed propeller... ?
Increases with increasing true air speed.
When it refers to blade angle it refers to the angle between the chord line and the direction of propeller rotation..the important bit in this question is that it is a constant speed prop, you are correct in that the angle of attack does decrease as forward speed increases and so the thrust decreases as well..therefore the rpm would increase, the csu would sense the increase in rpm and would then increase the blade angle to reduce the rpm down to the correct speed and restore the lost thrust.
Question 41-26 : A propeller blade is twisted, so as to ?
Keep the local angle of attack constant along the blade.
The angle of attack is the angle between the blade chord line and the relative airflow. trouble is, the relative airflow is different along the blade. the blade is rotating, so the bit nearest the hub has a small speed at right angles to the way the aircraft is going but the bit near the tip is moving rapidly across the aircraft flight path...to put real numbers on to this, a 10 ft blade doing 3000rpm will have a tip speed of about 300mph, so if the aircraft is going forward at 300mph the relative airflow is hitting the tip at 45deg off the aircraft centre line...thus, if you want the tip to have the same angle of attack as the root you have to twist the blade by 45deg along its length...the speed past the tip will now be more like 440mph in total, so if the angle of attack and the chord length were the same you would get a lot more lift thrust out toward the tip...but the only reason why you might not want the extra thrust is because it might bend the blade, and, if that worries you, you can taper the blade, reducing the chord length...blade design is always a compromise, but if you want best efficiency least fuel consumption in the cruise you will twist the blade so all sections reach their most efficient angle of attack at the same time.
Question 41-27 : A pilot can actuate the feathering system by ?
Pulling the propeller control lever rearwards.
Img884.by pulling the propeller control lever fully rearwards, you will feather the propeller to minimize drag in the event of an engine failure for example. in normal flight, you will pull or push the propeller control lever to adjust the blade pitch for the different phases of the flight climb, cruise and descent.. 885
Question 41-28 : When increasing true airspeed with a constant engine rpm, the angle of attack of a fixed pitch propeller ?
Reduces.
With fixed propellers, the throttle controls rpm..variations in forward speed affect the angle of attack, which varies in line with the amount of airflow into the propeller disc. if you increase speed, the angle of attack reduces, and if you slow down, it increases, affecting the lift/drag ratio, meaning that a fixed pitch propeller gets less efficient as you move away from its optimum speed, which is usually set for cruise.
Question 41-29 : A pressure relief valve in an oil system that does not seat correctly could result in ?
Low oil pressure.
To prevent too high a pressure, a pressure release valve prv is fitted. it comprises a stainless steel ball bearing and a spring..the ball is forced by the spring against an oil port. when the oil pressure is sufficiently high the ball if forced off its seat and oil is allowed to bypass this restriction thus making sure that the pressure never gets too high..if the pressure relief valve is not hermetic, there will be a leak and the pressure decreases.
Question 41-30 : In case of engine failure during flight the blades of a constant speed propeller in a single engine aeroplane, not fitted with feathering system ?
Move in the lowest pitch position by the centrifugal force and/or the spring force.
In the event of a problem causing the engine to stop, the propeller goes to minimum pitch in order to reduce drag and permits the pilot to try to restart the engine if possible. with less drag, you will have less propeller torque allowing a windmilling start. a constant speed propeller system will make use of the centrifugal force, oil or gas pressure or a spring to reduce the pitch.
Question 41-31 : For take off, the correct combination of propeller pitch 1 , and propeller lever position 2 at brake release is ?
1 low 2 forward.
Pushing the propeller control lever fully forward selects max rpm. in order to achieve this, the propeller goes to a fine pitch this is also called low pitch high pitch would be a coarse pitch position.. 884
Question 41-32 : For piston engines, mixture ratio is the ratio between the ?
Mass of fuel and mass of air entering the cylinder.
Question 41-33 : Variations in mixture ratios for carburettors are achieved by the adjustment of ?
Fuel flow.
Question 41-34 : As altitude increases, the mixture ratio of a piston engine should be adjusted to ?
Reduce the fuel flow in order to compensate for the decreasing air density.
Question 41-35 : When applying carburettor heating ?
The mixture becomes richer.
When you apply carburettor heating, the air which will mix with fuel in the carburettor passes around the muffler or exhaust pipe in order to be heated and to avoid the risks of icing. the air's density decreases as the air is heated, what generates a mixture mixture richer.
Question 41-36 : When the pilot moves the mixture lever of a piston engine towards a lean position the ?
Amount of fuel entering the combustion chamber is reduced.
Question 41-37 : When altitude increases without adjustment of the mixture ratio, the piston engine performance is affected because of a ?
A decrease of air density with a fuel flow which becomes too high.
Question 41-38 : A rich mixture setting has to be used during climb segments. this results in a ?
Lower cylinder head temperature.
To obtain the best torque during climb, you will have to decrease fuel entering in the carburettor in order to compensate the decreasing of the air density...a rich mixture will not permit to deliver the best available power, but it permits a lower cylinder head temperature.
Question 41-39 : Maximum exhaust gas temperature egt of a piston engine is theoretically associated with a ?
Fuel to air ratio of 1 15.
Egt is relative to the temperature of the charge as it burns within the cylinder. cht measures the temperature of the engine cylinder...the highest egt is achieved at a ratio of 15 parts of air to one part of fuel...if the ratio is reduced ie rich the charge temperature reduces due to excess fuel being left in the cylinder. if the ratio is greater than 15 1 ie lean or weak the charge is cooled by excess air. to appreciate why cht increases with lean mixtures we must consider the speed at which the fuel burns, ie its flame rate. lean mixtures burn slower than rich mixtures. this means more heat is transferred to the engine components with lean mixtures...example. if you move a lighted match quickly under you hand, no problem, but move it slowly and you will burn your hand slow burning lean mixtures will increase cht.
Question 41-40 : For a given type of oil, the oil viscosity depends on the ?
Oil temperature.
Feedback. Your feedback on our MCQs or on your own exams is essential to improve our offer and offer you the best possible content. Share your impressions with us to help us optimize our services and better meet your revision needs EASA Certification Exam.
Exclusive rights reserved. Reproduction prohibited under penalty of prosecution.
