Question 42-1 : The fuel temperature at which under standard conditions the vapour ignites in contact with a flame and extinguishes immediately is the ? [ Mandatory security ]

Question 42-2 : A fuel strainer fuel filter when fitted to a carburettor will be positioned ?

Upstream of the needle valve.

A fuel strainer is a fuel filterthe fuel need to be filtered before entering the carburettor 887

Question 42-3 : The working cycle of a four stroke engine is ?

Induction compression power exhaust.

Question 42-4 : Specific fuel consumption is defined as the ?

Mass of fuel required to produce unit power for unit time.

Question 42-5 : The purpose of the contact breaker is to ?

Control the primary circuit of the magneto.

Question 42-6 : Under normal running conditions a magneto draws primary current ?

From a self contained electro magnetic induction system.

Question 42-7 : The air in a piston engine turbo supercharger centrifugal compressor ?

Enters the eye of the impeller and leaves at a tangent to the periphery.

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

Question 42-8 : The power of a piston engine which will be measured by a friction brake is ?

Brake horse power.

Question 42-9 : The power output of a piston engine can be calculated by ?

Torque times rpm.

Question 42-10 : The power of a piston engine decreases during a climb with a constant power lever setting because of the decreasing ?

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

Question 42-11 : The torque of an aeroplane engine can be measured at the ?

Question 42-12 : The conditions most likely to produce the highest engine power are ?

Cold and dry air at high pressure.

Hot low pressure air contains fewer oxygen molecules per cubic meter or foot than cold high pressure airwater molecules humidity displace a certain amount of the oxygen in the engine air intake meaning that the engine inhales less oxy

Question 42-13 : The kind of compressor normally used as a supercharger is ?

Question 42-14 : An egt exhaust gas temperature indicator for a piston engine is used to ?

Assist the pilot to set the correct mixture.

Question 42-15 : The conditions which can cause detonation are ?

High manifold pressure and low revolutions per minute.

High pressure and temperature in the cylinder cause detonation this is when the fuelair mixture explodes rather than burns high manifold pressure and low revolutions would cause this conditionthe grade of fuel used in an engine must ensure that detonation doesn't occur during the engine's normal operating range for temperature and pressure a lower octane fuel allows detonation to occur at lower temperatures and pressures but it doesn't actually cause detonation

Question 42-16 : If the manifold pressure is increased the blade angle of a constant speed propeller ?

It will increase.

Manifold pressure controls the blade angle of a constant speed propeller also know as a variable pitch propeller a constant speed performs pretty much the same function as a gearbox does in a car in that it 'maintains engine rpm over a varying conditions of road' the gearbox or constant speed prop is there because engine work best within a certain range of rpm going too fast or too slow is not good for themthe manifold absolute pressure map indicates the power output of a piston engine and if it is increased the blade angle will increase as if you climb in mountain for a car a lower gear will give more torque fine pitch will give more thurst

Question 42-17 : The 'slipstream effect' of a propeller is most prominent at ?

Low airspeeds with high power setting.

The high speed rotation of an airplane propeller gives a corkscrew or spiraling rotation to the slipstreamat high propeller speeds and low forward speed as in the takeoffs and approaches to power on stalls this spiraling rotation is very compact and exerts a strong sideward force on the airplane's vertical tail surface 892when this spiraling slipstream strikes the vertical fin on the left it causes a left turning moment about the airplane's vertical axis the more compact the spiral the more prominent this force is as the forward speed increases however the spiral elongates and becomes less effectivethe corkscrew flow of the slipstream also causes a rolling moment around the longitudinal axisnote that this rolling moment caused by the corkscrew flow of the slipstream is to the right while the rolling moment caused by torque reaction is to the left in effect one may be counteracting the other however these forces vary greatly and it is up to the pilot to apply proper correction action by use of the flight controls at all times these forces must be counteracted regardless of which is the most prominent at the time

Question 42-18 : The operating principle of float type carburettors is based on the ?

Difference in air pressure at the venturi throat and the air inlet.

The carburattor uses the venturi principle as the speed of air increases through the choke the pressure reduces enough to pull fuel into it via the main nozzle which is connected directly to the fuel system through a series of pumps and jets

Question 42-19 : The crank assembly of a piston engine comprises the ?

Crankshaft connecting rods and pistons.

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Question 42-20 : On four stroke piston engines the theoretical valve and ignition settings are readjusted in order to increase the ?

Overall efficiency.

Question 42-21 : For internal cooling reciprocating engines are especially dependent on ?

The circulation of lubricating oil.

Question 42-22 : The main purpose of the mixture control is to ?

Adjust the fuel flow to obtain the correct fuelair ratio.

Question 42-23 : In which sections of the carburettor would icing most likely occur ?

Venturi and the throttle valve.

Question 42-24 : For a reciprocating engine fuelair ratio or mixture is the ratio between the ?

Mass of fuel and mass of air entering the cylinder.

The most accurate measure that you can get is the mass of the air and fuel because it is compensating for the density volume changes with temperaturethe 15 1 is therefore 15 parts of air by weight to 1 part of fuel by weight

Question 42-25 : Which statement is correct concerning the effect of the application of carburettor heat ?

The density of the air entering the carburettor is reduced thus enriching the fuelair mixture.

When you apply carburettor heat to melt ice that has formed in the throat or venturi the air entering to mix with fuel passes around the exhaust pipe to be heated this heated air has its density reducesthe volume of air does not change when you apply carburettor heat

Question 42-26 : Vapour lock is ?

Question 42-27 : The reading on the oil pressure gauge is the ?

Pressure of the oil on the outlet side of the pressure pump.

Question 42-28 : The main purpose of a turbocharger is to ?

Maintain power with increasing altitude.

Question 42-29 : An excessively rich mixture can be detected by ?

Black smoke from exhaust.

Question 42-30 : The compression ratio of a piston engine is the ratio of the ?

Volume of the cylinder with the piston at bottom dead centre to that with the piston at top dead centre.

Img897compression ratio = volume at bottom dead volume at top dead

Question 42-31 : The purpose of the venturi in a carburettor is to ?

Create the suction necessary to cause fuel to flow through the carburettor main jets.

Question 42-32 : The mixture controller of a carburettor ?

Varies the fuel supply to the main discharge nozzle.

Question 42-33 : A turbocharger system in a reciprocating engine is normally driven by ?

The exhaust system.

Img891this short illustration explains clearly the principle

Question 42-34 : An aircraft magneto is switched off by 1 grounding the primary circuit2 opening the primary circuit3 opening the secondary circuit4 grounding the secondary circuitthe combination that regroups all of the correct statements is ?

1 4.

A magneto is essentially a self contained generator which is gear driven by the enginethe ignition switch in the cockpit when selected off ground the magnetos to earth through the primary circuitit works also for the secondary circuit but usually this is the primary circuit which is grounded

Question 42-35 : Spark timing is related to engine speed in the way that the ?

Faster the engine functions the more the spark is advanced.

The ignition timing of a piston engine needs to be advanced at 'high rpm' because flame rate and time for complete combustion remain constant

Question 42-36 : An impulse magneto coupling ?

Gives a retarded spark at starting.

The impulse coupling is a spring loaded mechanical coupling which delays rotation of the magneto during an engine start after a short period of rotation the device allows the magneto to catch upin effect spinning the mag shaft faster than the engine is turning it the faster it turns the hotter the spark and the bigger the voltage impulsemaking for easier starting after the engine is running rotational forces move the spring loaded arms which make the impulse coupling work at low speeds out of the way the impulse coupling only works at very low engine speeds

Question 42-37 : If an engine fails to stop with the magneto switch in off position the cause may be ?

Excessive carbon formation in cylinder head.

The magneto switch controls the primary magneto circuit by grounding it this is done to isolate individual magnetos during the rpm drop checkif this wire is broken and therefore cannot be earthed then the magneto will continue to supply current to the engine and it will continue to runthe correct answer as stated is excessive carbon formation this forms hot spots which remain heated and continue to ignite the mixture even though the plugs are not sparking

Question 42-38 : An impulse coupling is installed on a magneto of a piston engine to ?

Provide a stronger spark on top dead centre for engine starting.

The impulse coupling is a spring loaded mechanical coupling which delays rotation of the magneto during an engine start after a short period of rotation the device allows the magneto to catch upin effect spinning the mag shaft faster than the engine is turning it the faster it turns the hotter the spark and the bigger the voltage impulse making for easier starting after the engine is running rotational forces move the spring loaded arms which make the impulse coupling work at low speeds out of the way the impulse coupling only works at very low engine speeds

Question 42-39 : The part of a piston engine that transforms reciprocating movement into rotary motion is termed the ?

Crankshaft.

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Question 42-40 : In a piston engine if the ratio of air to fuel is approximately 9 1 the mixture is ?

Rich.

Rich 9 1correct 15 1weak 20 1