The conditions which can cause detonation are ? [ Observation CPL ]

Question 29-1 : High manifold pressure and low revolutions per minute low manifold pressure and high revolutions per minute high manifold pressure and high revolutions per minute low manifold pressure and high fuel flow

exemple 129 High manifold pressure and low revolutions per minute. — High pressure and temperature in the cylinder cause detonation this is when the fuel/air mixture explodes rather than burns .high manifold pressure and low revolutions would cause this condition .the 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 High manifold pressure and low revolutions per minute.

If the manifold pressure is increased the blade angle of a constant speed ?

Question 29-2 : It will increase will increase and after a short time will reduce will reduce so that the engine rpm can increase will remain the same

exemple 133 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 them .the 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 It will increase.

The 'slipstream effect' of a propeller is most prominent at ?

Question 29-3 : Low airspeeds with high power setting high airspeeds with low power setting high airspeeds with high power setting low airspeeds with low power setting

exemple 137 Low airspeeds with high power setting. — The high speed rotation of an airplane propeller gives a corkscrew or spiraling rotation to the slipstream .at 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 . 892.when 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 effective .the corkscrew flow of the slipstream also causes a rolling moment around the longitudinal axis .note 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 Low airspeeds with high power setting.

The operating principle of float type carburettors is based on the ?

Question 29-4 : Difference in air pressure at the venturi throat and the air inlet automatic metering of air at the venturi as the aircraft gains altitude increase in air velocity in the throat of a venturi causing an increase in air pressure measurement of the fuel flow into the induction system

exemple 141 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 Difference in air pressure at the venturi throat and the air inlet.

The crank assembly of a piston engine comprises the ?

Question 29-5 : Crankshaft connecting rods and pistons propeller crankshaft pistons and connecting rods crankcase crankshaft connecting rods and pistons crankshaft camshaft valves valve springs and push rods

exemple 145 Crankshaft, connecting rods and pistons. — Img893 Crankshaft, connecting rods and pistons.

The purpose of the blow in doors at the air inlets is to ?

Question 29-6 : Provide the engine with additional air at high power settings and low air speeds serve to increase the relative velocity at the first compressor stage provide the engine with additional air at high power settings at cruising speed feed cooling air to the engine cowling

exemple 149 Provide the engine with additional air at high power settings and low air speeds. — Spring loaded doors located in the inlet duct of some gas turbine or turbofan engines these doors are normally closed but they open under conditions of low speed and high engine power to permit additional air into the compressor .blow in doors help prevent compressor stall .here are some examples . 896. 895 Provide the engine with additional air at high power settings and low air speeds.

On four stroke piston engines the theoretical valve and ignition settings are ?

Question 29-7 : Overall efficiency compression ratio piston displacement engine rpm

exemple 153 Overall efficiency. — Overall efficiency.

For internal cooling reciprocating engines are especially dependent on ?

Question 29-8 : The circulation of lubricating oil a rich fuel/air mixture a lean fuel/air mixture a properly functioning thermostat

exemple 157 The circulation of lubricating oil — The circulation of lubricating oil

The main purpose of the mixture control is to ?

Question 29-9 : Adjust the fuel flow to obtain the correct fuel/air ratio decrease the air supplied to the engine increase the oxygen supplied to the engine decrease the oxygen supplied to the engine

exemple 161 Adjust the fuel flow to obtain the correct fuel/air ratio. — Adjust the fuel flow to obtain the correct fuel/air ratio.

In which sections of the carburettor would icing most likely occur ?

Question 29-10 : Venturi and the throttle valve accelerator pump and main metering jet main air bleed and main discharge nozzle float chamber and fuel inlet filter

exemple 165 Venturi and the throttle valve. — Venturi and the throttle valve.

For a reciprocating engine fuel/air ratio or mixture is the ratio between the ?

Question 29-11 : Mass of fuel and mass of air entering the cylinder volume of fuel and volume of air entering the carburettor volume of fuel and volume of air entering the cylinder mass of fuel and mass of air entering the carburettor

exemple 169 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 temperature .the 15 1 is therefore 15 parts of air by weight to 1 part of fuel by weight Mass of fuel and mass of air entering the cylinder.

Which statement is correct concerning the effect of the application of ?

Question 29-12 : The density of the air entering the carburettor is reduced thus enriching the fuel/air mixture the volume of air entering the carburettor is reduced thus enriching the fuel/air mixture the volume of air entering the carburettor is reduced thus leaning the fuel/air mixture the density of the air entering the carburettor is reduced thus leaning the fuel/air mixture

exemple 173 The density of the air entering the carburettor is reduced, thus enriching the fuel/air 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 reduces .the volume of air does not change when you apply carburettor heat The density of the air entering the carburettor is reduced, thus enriching the fuel/air mixture.

Vapour lock is ?

Question 29-13 : Vaporizing of fuel prior to reaching the carburettor the formation of water vapour in a fuel system vaporizing of fuel in the carburettor the inability of a fuel to vaporize in the carburettor

exemple 177 Vaporizing of fuel prior to reaching the carburettor — Vaporizing of fuel prior to reaching the carburettor

The reading on the oil pressure gauge is the ?

Question 29-14 : Pressure of the oil on the outlet side of the pressure pump difference between the pressure pump pressure and the scavenge pump pressure pressure in the oil tank reservoir pressure of the oil on the inlet side of the pressure pump

The main purpose of a turbocharger is to ?

Question 29-15 : Maintain power with increasing altitude reduce the fuel flow provide a leaner mixture at sea level provide a richer mixture at high altitudes

exemple 185 Maintain power with increasing altitude. — Maintain power with increasing altitude.

An excessively rich mixture can be detected by ?

Question 29-16 : Black smoke from exhaust white smoke from exhaust high cylinder head temperatures a long purple flame from exhaust

The compression ratio of a piston engine is the ratio of the ?

Question 29-17 : Volume of the cylinder with the piston at bottom dead centre to that with the piston at top dead centre diameter of the bore to the piston stroke area of the piston to the cylinder volume weight of the air induced to its weight after compression

exemple 193 Volume of the cylinder with the piston at bottom dead centre to that with the piston at top dead centre. — Img897.compression ratio = volume at bottom dead / volume at top dead. Volume of the cylinder with the piston at bottom dead centre to that with the piston at top dead centre.

The purpose of the venturi in a carburettor is to ?

Question 29-18 : Create the suction necessary to cause fuel to flow through the carburettor main jets prevent enrichment of the mixture due to high air velocity through the carburettor ensure complete atomisation of the fuel before entering the injection system create a rise in pressure at the throat before the mixture enters the induction system

exemple 197 Create the suction necessary to cause fuel to flow through the carburettor main jets. — Create the suction necessary to cause fuel to flow through the carburettor main jets.

The mixture controller of a carburettor ?

Question 29-19 : Varies the fuel supply to the main discharge nozzle varies the air supply at the main discharge nozzle alters the pressure drop at the main discharge nozzle moves the butterfly valve through a separate linkage to the main throttle control

exemple 201 Varies the fuel supply to the main discharge nozzle. — Varies the fuel supply to the main discharge nozzle.

A turbocharger system in a reciprocating engine is normally driven by ?

Question 29-20 : The exhaust system an electric motor an hydraulic motor an electrically activated hydraulically powered clutch

exemple 205 The exhaust system. — Img891.this short illustration explains clearly the principle The exhaust system.

An aircraft magneto is switched off by .1 grounding the primary circuit .2 ?

Question 29-21 : 1 4 2 3 1 3 2 4

exemple 209 1, 4. — .a magneto is essentially a self contained generator which is gear driven by the engine .the ignition switch in the cockpit when selected off ground the magnetos to earth through the primary circuit .it works also for the secondary circuit but usually this is the primary circuit which is grounded 1, 4.

Spark timing is related to engine speed in the way that the ?

Question 29-22 : Faster the engine functions the more the spark is advanced slower the engine functions the more the spark is advanced faster the engine functions the further past tdc the spark occurs faster the engine functions the more retarded the spark is

exemple 213 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 Faster the engine functions, the more the spark is advanced.

An impulse magneto coupling ?

Question 29-23 : Gives a retarded spark at starting reduces magneto speed during engine warm up advances ignition timing and gives a hotter spark at starting gives an automatic spark increase during high speed operation

exemple 217 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 up in 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 Gives a retarded spark at starting.

If an engine fails to stop with the magneto switch in off position the cause ?

Question 29-24 : Excessive carbon formation in cylinder head defective condenser fouled spark plugs switch wire grounded

exemple 221 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 check .if 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 run .the 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 Excessive carbon formation in cylinder head.

An impulse coupling is installed on a magneto of a piston engine to ?

Question 29-25 : Provide a stronger spark on top dead centre for engine starting advance the ignition timing facilitate quick removal and installation absorb starting loads

exemple 225 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 up in 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 Provide a stronger spark on top dead centre for engine starting.

The part of a piston engine that transforms reciprocating movement into rotary ?

Question 29-26 : Crankshaft piston camshaft reduction gear

exemple 229 Crankshaft. — Img893 Crankshaft.

In a piston engine if the ratio of air to fuel is approximately 9 1 the mixture ?

Question 29-27 : Rich weak too weak to support combustion chemically correct

exemple 233 Rich. — Rich 9 1.correct 15 1.weak 20 1 Rich.

Spark plug fouling is more likely to happen if ?

Question 29-28 : The aircraft descends continuously at idle power the aircraft cruises at low speed with the correct mixture power is increased too abruptly the engine runs at maximum continuous power for too long

exemple 237 The aircraft descends continuously at idle power. — .plug fouling can occur due to rich mixtures with low cylinder temperatures this is the condition the engine will be in during descent at idle power .this is the reason during your flight training you are told not to let the engine run at idle rpm for too long normally you would increase rpm to around 1000 1200 rpm The aircraft descends continuously at idle power.

To maintain a constant mixture at low and high power settings in a piston ?

Question 29-29 : A diffuser compensating jet a power jet an accelerator pump a mixture control

As engine speed and airflow through the venturi increase the proportion of fuel to air rises as a result of the different flow characteristics of the two fluids this causes the mixture to become richer .to overcome this effect some carburettors are fitted with a diffuser compensating jet .as engine speed is progressively increased above idling the fuel level in the diffuser well drops and progressively uncovers more air holes these holes allow more air into the discharge tube and by reducing the pressure differential prevent enrichment of the air/fuel mixture .the process of drawing both air and fuel through the discharge tube also has the effect of vaporising the fuel more readily particularly at low engine speeds

A piston engine may use a fuel of a different grade than the recommended ?

Question 29-30 : Provided that the grade is higher provided that the grade is lower never provided that it is an aeronautical petrol

exemple 245 Provided that the grade is higher — Provided that the grade is higher

In very cold weather the pilot notices during startup a slightly higher than ?

Question 29-31 : Is normal if it decreases after startup is abnormal and requires the engine to be shut down is abnormal but does not require the engine to be shut down requires an oil change

Excessive pressure in the cylinders of an engine equipped with a constant speed ?

Question 29-32 : High manifold pressure and low rpm low manifold pressure and low rpm high manifold pressure and high rpm low manifold pressure and high rpm

exemple 253 High manifold pressure and low rpm. — With constant speed control the pitch of the variable pitch propeller is changed automatically by a governor after the pilot sets the desired engine/propeller speed with the propeller speed control the governor acts to keep the propeller speed at the same value if the governor detects the propeller speed increasing it increases the pitch a little to bring the speed back within limits if the governor detects the propeller speed decreasing it decreases the pitch a little to bring the speed again back within limits this operation may be compared to an automatic gearbox in an automobile where the gears are changed automatically to keep the engine operating at a reasonable speed .during a power change on an engine equipped with a constant speed propeller a wrong combination of manifold pressure and rpm values results in excessive pressures in the cylinders this is the case when one simultaneously selects a high manifold pressure and low rpm High manifold pressure and low rpm.

When in flight a piston engine is stopped and the propeller blade angle is near ?

Question 29-33 : Feathered windmilling transparent at zero drag

The richness of a fuel/air mixture ratio is the ?

Question 29-34 : Real mixture ratio relative to the theoretical ratio volume of fuel relative to the volume of air volume of fuel relative to the mass of the volume of air mass of fuel relative to the volume of air

exemple 261 Real mixture ratio relative to the theoretical ratio. — As the name implies mixture refers to the ratio of fuel/air that goes into the cylinders of an engine for combustion for an internal combustion engine to operate it requires three things fuel air and ignition fuel and air are mixed in a ratio of approximately 15 1 15 parts of air to every 1 part of fuel to create combustion in a carbureted engine non fuel injected fuel and air are mixed in the carburetor before being introduced into the cylinders .carburetors are calibrated to operate with the mixture control set to 'full rich' when operating at sea level as the aircraft gains altitude it becomes necessary to reduce the amount of fuel entering the carburetor because the amount of air is automatically decreasing with altitude due to lower atmospheric pressure if the pilot fails to decrease the amount of fuel as altitude is gained the result will be an overly 'rich' mixture creating problems such as fouled spark plugs and excessive fuel consumption .overheating problems tend to occur when operating with an excessively lean mixture too little fuel a lean mixture creates better performance to a point as well as higher operating temperatures and reduces fuel consumption the problem arises when pilots fail to enrichen mixture add fuel as altitude is lost during a descent this results in an excessively lean mixture which can cause engine roughness fuel starvation and even permanent engine damage the point to remember is that fuel mixture must be decreased leaned as the aircraft climbs and increased enrichened as the aircraft descends it is also suggested to lean the mixture during ground operations at higher altitude airports generally above 3000 ft amsl .the term 'richness' refers to the 'real mixture ratio' relative to the 'theoretical mixture ratio' Real mixture ratio relative to the theoretical ratio.

Dual ignition provides a factor of reliability and ?

Question 29-35 : Improves combustion efficiency provides more voltage aids in starting saves wear caused by using one magneto constantly

exemple 265 Improves combustion efficiency. — Improves combustion efficiency.

With a piston engine when detonation is recognised you ?

Question 29-36 : Reduce manifold pressure and enrich the mixture increase manifold pressure and lean the mixture reduce manifold pressure and lean the mixture increase manifold pressure and enrich the mixture

exemple 269 Reduce manifold pressure and enrich the mixture. — The sudden release of heat energy from fuel in an aircraft engine caused by the fuel air mixture reaching its critical pressure and temperature .detonation occurs as a violent explosion rather than a smooth burning process .when detonation is recognized you should reduce manifold pressure and enrich the mixture .detonation can be caused by . too lean mixture. too high manifold pressure. using low grade fuel. an overheated engine Reduce manifold pressure and enrich the mixture.

'vapour lock' is the phenomenon by which ?

Question 29-37 : Heat produces vapour bubbles in the fuel line water vapour plugs are formed in the intake fuel line following the condensation of water in fuel tanks which have not been drained for sometime burnt gas plugs forming and remaining in the exhaust manifold following an overheat and thereby disturbing the exhaust abrupt and abnormal enrichment of the fuel/air mixture following an inappropriate use of carburettor heat

exemple 273 Heat produces vapour bubbles in the fuel line. — The vapour lock is a stoppage in a fuel feeding line caused by a fuel vapour bubble Heat produces vapour bubbles in the fuel line.

For a piston engine the chemically correct fuel/air ratio ?

Question 29-38 : Is 1 15 is 1 9 is 1 5 is 1 12

exemple 277 Is 1:15 — Rich 9 1.correct 15 1.weak 20 1 Is 1:15

The function of the primer pump in a reciprocating engine is to ?

Question 29-39 : Provide additional fuel for an engine start serve as an alternate pump in case of an engine driven pump failure to serve as main supply pump in a fuel injection system inject additional fuel during engine acceleration

exemple 281 Provide additional fuel for an engine start. — Provide additional fuel for an engine start.

One of the advantages of a turbocharger is ?

Question 29-40 : To make the power available less affected by altitude an increased propulsive efficiency that there is no torsion at the crankshaft that there is no danger of detonation

exemple 285 To make the power available less affected by altitude. — To make the power available less affected by altitude.

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