A constant speed drive aims at ensuring ? [ Professional DGAC ]

Question 28-1 : That the electric generator produces a constant frequency that the starter motor maintains a constant rpm not withstanding the acceleration of the engine that the csd remains at a constant rpm not withstanding the generator rpm equal ac voltage from all generators

exemple 128 That the electric generator produces a constant frequency. — That the electric generator produces a constant frequency.

When a persistent underexcitation fault is detected on an ac generator ?

Question 28-2 : The exciter control relay the generator breaker and the tie breaker the generator breaker and the tie breaker the generator control relay and the generator breaker the tie breaker

exemple 132 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 The exciter control relay, the generator breaker and the tie breaker.

A test to assess the state of charge of a lead acid battery would involve ?

Question 28-3 : Comparing the 'on load' and 'off load' battery voltages checking the level of the electrolyte checking the discharge current of the battery 'on load' checking the battery voltage 'off load'

exemple 136 Comparing the 'on-load' and 'off-load' battery voltages. — Comparing the 'on-load' and 'off-load' battery voltages.

The advantages of grounding the negative pole of the aircraft structure are . 1 ?

Question 28-4 : 1 2 4 1 2 3 2 3 5 1 3 5

exemple 140 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 1, 2, 4.

When an 'open circuit' occurs in an electrical supply system the ?

Question 28-5 : Loss of continuity will prevent its working components from functioning load as indicated by the ammeter will increase fuse or cb should isolate the circuit due to excess current drawn component will operate normally but will not switch off

exemple 144 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 Loss of continuity will prevent its working components from functioning.

An ac generator driven by a csd unit ?

Question 28-6 : Requires a voltage controller to maintain constant voltage under load does not need a voltage controller since the csd will ensure constant voltage does not need a voltage controller since an ac generator voltage cannot alter under load requires a voltage controller to maintain constant frequency

exemple 148 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 Requires a voltage controller to maintain constant voltage under load.

Consider the variable pitch propeller of a turbo prop during deceleration ?

Question 28-7 : When braking the propeller supplies negative thrust and absorbs engine power at zero power the propeller thrust is zero and the engine power absorbed is nil when feathered the propeller produces thrust and absorbs no engine power with propeller windmilling the thrust is zero and the propeller supplies engine power

exemple 152 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 When braking, the propeller supplies negative thrust and absorbs engine power.

The correct formula to calculate the total displacement of a multi cylinder ?

Question 28-8 : Piston area x piston stroke x number of cylinders piston area x piston stroke cylinder volume x number of cylinders cylinder length x cylinder diameter

exemple 156 Piston area x piston stroke x number of cylinders — Piston area x piston stroke x number of cylinders

When changing power on engines equipped with constant speed propeller engine ?

Question 28-9 : Increasing the rpm before increasing the manifold pressure reducing the rpm before reducing the manifold pressure adjusting fuel flow before the manifold pressure increasing the manifold pressure before increasing the rpm

exemple 160 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 Increasing the rpm before increasing the manifold pressure.

The blade angle of a constant speed propeller ?

Question 28-10 : Increases with increasing true air speed only varies with engine rpm decreases with increasing true air speed is independent of the true air speed

exemple 164 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 Increases with increasing true air speed.

A propeller blade is twisted so as to ?

Question 28-11 : Keep the local angle of attack constant along the blade avoid the appearance of sonic phenomena decrease the blade tangential velocity from the blade root to the tip allow a higher mechanical stress

exemple 168 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 Keep the local angle of attack constant along the blade.

A pilot can actuate the feathering system by ?

Question 28-12 : Pulling the propeller control lever rearwards pushing the propeller control lever forwards pulling the power levers rearwards pushing the power lever forwards

exemple 172 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 Pulling the propeller control lever rearwards.

When increasing true airspeed with a constant engine rpm the angle of attack of ?

Question 28-13 : Reduces increases stays constant stays constant because it only varies with engine rpm

exemple 176 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 Reduces.

A pressure relief valve in an oil system that does not seat correctly could ?

Question 28-14 : Low oil pressure high oil pressure low oil temperature excessive oil consumption

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

In case of engine failure during flight the blades of a constant speed ?

Question 28-15 : Move in the lowest pitch position by the centrifugal force and/or the spring force move in low pitch position by oil pressure created by the windmilling propeller move in a certain pitch position depending on windmilling rpm move in the highest pitch position by the aerodynamic force

exemple 184 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 Move in the lowest pitch position by the centrifugal force and/or the spring force.

For take off the correct combination of propeller pitch 1 and propeller lever ?

Question 28-16 : 1 low 2 forward 1 high 2 forward 1 low 2 aft 1 high 2 aft

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

For piston engines mixture ratio is the ratio between the ?

Question 28-17 : Mass of fuel and mass of air entering the cylinder volume of fuel and volume of air entering the cylinder volume of fuel and volume of air entering the carburettor mass of fuel and volume of air entering the carburettor

exemple 192 Mass of fuel and mass of air entering the cylinder. — Mass of fuel and mass of air entering the cylinder.

Variations in mixture ratios for carburettors are achieved by the adjustment of ?

Question 28-18 : Fuel flow air flow fuel flow air flow and temperature fuel flow and air flow

As altitude increases the mixture ratio of a piston engine should be adjusted to ?

Question 28-19 : Reduce the fuel flow in order to compensate for the decreasing air density reduce the fuel flow in order to compensate for the increasing air density increase the mixture ratio increase the fuel flow in order to compensate for the decreasing air pressure and density

exemple 200 Reduce the fuel flow in order to compensate for the decreasing air density. — Reduce the fuel flow in order to compensate for the decreasing air density.

When applying carburettor heating ?

Question 28-20 : The mixture becomes richer the mixture becomes leaner a decrease in rpm results from the lean mixture no change occurs in the mixture ratio

exemple 204 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 The mixture becomes richer.

When the pilot moves the mixture lever of a piston engine towards a lean ?

Question 28-21 : Amount of fuel entering the combustion chamber is reduced volume of air entering the carburettor is reduced amount of fuel entering the combustion chamber is increased volume of air entering the carburettor is increased

exemple 208 Amount of fuel entering the combustion chamber is reduced. — Amount of fuel entering the combustion chamber is reduced.

When altitude increases without adjustment of the mixture ratio the piston ?

Question 28-22 : A decrease of air density with a fuel flow which becomes too high an increase of air density with a fuel flow which becomes too high an increase of air density with a fuel flow which becomes too low a decrease of air density with a fuel flow which becomes too low

exemple 212 A decrease of air density with a fuel flow which becomes too high. — A decrease of air density with a fuel flow which becomes too high.

A rich mixture setting has to be used during climb segments this results in a ?

Question 28-23 : Lower cylinder head temperature higher efficiency increase of power higher torque

exemple 216 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 Lower cylinder head temperature.

Maximum exhaust gas temperature egt of a piston engine is theoretically ?

Question 28-24 : Fuel to air ratio of 1 15 cruising mixture setting full rich setting mixture ratio very close to idle cut out

exemple 220 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 Fuel to air ratio of 1:15.

For a given type of oil the oil viscosity depends on the ?

Question 28-25 : Oil temperature outside pressure oil pressure quantity of oil

exemple 224 Oil temperature. — Oil temperature.

The fuel temperature at which under standard conditions the vapour ignites in ?

Question 28-26 : Flash point fire point combustion point self ignition point

Pre ignition refers to the condition that may arise when ?

Question 28-27 : The mixture is ignited by abnormal conditions within the cylinder before the spark occurs at the plug the mixture is ignited before the piston has reached top dead centre a rich mixture is ignited by the sparking plugs the sparking plug ignites the mixture too early

exemple 232 The mixture is ignited by abnormal conditions within the cylinder before the spark occurs at the plug — The mixture is ignited by abnormal conditions within the cylinder before the spark occurs at the plug

A fuel strainer fuel filter when fitted to a carburettor will be positioned ?

Question 28-28 : Upstream of the needle valve between the needle valve and the metering jet between the metering jet and the discharge nozzle downstream of the discharge nozzle

exemple 236 Upstream of the needle valve. — A fuel strainer is a fuel filter .the fuel need to be filtered before entering the carburettor . 887 Upstream of the needle valve.

The working cycle of a four stroke engine is ?

Question 28-29 : Induction compression power exhaust induction power compression exhaust induction compression expansion power compression induction power exhaust

exemple 240 Induction, compression, power, exhaust. — Induction, compression, power, exhaust.

Specific fuel consumption is defined as the ?

Question 28-30 : Mass of fuel required to produce unit power for unit time maximum fuel consumption of the aircraft designed fuel consumption for a given rpm quantity of fuel required to run the engine for one minute at maximum operating conditions

exemple 244 Mass of fuel required to produce unit power for unit time. — Mass of fuel required to produce unit power for unit time.

The purpose of the contact breaker is to ?

Question 28-31 : Control the primary circuit of the magneto connect the secondary coil to the distributor connect the battery to the magneto connect the contact breaker and condenser in series with the primary coil

exemple 248 Control the primary circuit of the magneto. — Control the primary circuit of the magneto.

Under normal running conditions a magneto draws primary current ?

Question 28-32 : From a self contained electro magnetic induction system from the booster coil from the aircraft batteries via an inverter directly from the aircraft batteries

exemple 252 From a self-contained electro-magnetic induction system. — From a self-contained electro-magnetic induction system.

The air in a piston engine turbo supercharger centrifugal compressor ?

Question 28-33 : Enters the eye of the impeller and leaves at a tangent to the periphery enters via the diffuser and is fed to the impeller at the optimum angle of attack enters at the periphery and leaves via the eye of the impeller enters at a tangent to the rotor and leaves via the stator

exemple 256 Enters the eye of the impeller and leaves at a tangent to the periphery. — Img889. 890.the air in a piston engine turbo supercharger centrifugal compressor enters the eye of the impeller and leaves at a tangent to the periphery Enters the eye of the impeller and leaves at a tangent to the periphery.

The power of a piston engine which will be measured by a friction brake is ?

Question 28-34 : Brake horse power frictional horse power heat loss power indicated horse power

exemple 260 Brake horse power. — Brake horse power.

The power output of a piston engine can be calculated by ?

Question 28-35 : Torque times rpm work times velocity force times distance pressure times arm

exemple 264 Torque times rpm. — Torque times rpm.

The power of a piston engine decreases during a climb with a constant power ?

Question 28-36 : Air density engine temperature humidity temperature

exemple 268 Air density. — Howarthson .note in this question 'with a constant power lever setting' so as you climb the power will be decreasing because the air is becoming less dense so manifold absolute pressure will be decreasing Air density.

The torque of an aeroplane engine can be measured at the ?

Question 28-37 : Gear box which is located between the engine and the propeller accessory gear box propeller blades camshaft

exemple 272 Gear box which is located between the engine and the propeller. — Gear box which is located between the engine and the propeller.

The conditions most likely to produce the highest engine power are ?

Question 28-38 : Cold and dry air at high pressure warm air at low pressure with high relative humidity cold air at high pressure with high relative humidity warm and dry air at high pressure

exemple 276 Cold and dry air at high pressure. — Hot low pressure air contains fewer oxygen molecules per cubic meter or foot than cold high pressure air .water molecules humidity displace a certain amount of the oxygen in the engine air intake meaning that the engine inhales less oxygen Cold and dry air at high pressure.

The kind of compressor normally used as a supercharger is ?

Question 28-39 : A radial compressor an axial compressor a hybrid compressor a piston compressor

exemple 280 A radial compressor. — Img891.the compressor section is fitted with a radial compressor .turbine section can be radial or axial A radial compressor.

An egt exhaust gas temperature indicator for a piston engine is used to ?

Question 28-40 : Assist the pilot to set the correct mixture control the cylinder head temperature control the carburettor inlet air flow control the fuel temperature

exemple 284 Assist the pilot to set the correct mixture. — Assist the pilot to set the correct mixture.

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