Question 43-1 : Spark plug fouling is more likely to happen if ? [ Skills lift off ]

Question 43-2 : To maintain a constant mixture at low and high power settings in a piston engine a carburettor is fitted with ?

A diffuser compensating jet .

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 richerto 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 airfuel mixturethe 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

Question 43-3 : A piston engine may use a fuel of a different grade than the recommended ?

Provided that the grade is higher.

Question 43-4 : In very cold weather the pilot notices during startup a slightly higher than normal engine oil pressure this higher pressure ?

Is normal if it decreases after startup.

Question 43-5 : Excessive pressure in the cylinders of an engine equipped with a constant speed propeller can be caused by the combination of ?

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 enginepropeller 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 speedduring 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

Question 43-6 : When in flight a piston engine is stopped and the propeller blade angle is near 90° the propeller is said to be ?

Feathered.

Question 43-7 : The richness of a fuelair mixture ratio is the ?

Real mixture ratio relative to the theoretical ratio.

As the name implies mixture refers to the ratio of fuelair 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 cylinderscarburetors 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 consumptionoverheating 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'

Question 43-8 : Dual ignition provides a factor of reliability and ?

Improves combustion efficiency.

Question 43-9 : With a piston engine when detonation is recognised you ?

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 temperaturedetonation occurs as a violent explosion rather than a smooth burning processwhen detonation is recognized you should reduce manifold pressure and enrich the mixturedetonation can be caused by too lean mixture too high manifold pressure using low grade fuel an overheated engine

Question 43-10 : 'vapour lock' is the phenomenon by which ?

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

Question 43-11 : For a piston engine the chemically correct fuelair ratio ?

Is 1 15.

Rich 9 1correct 15 1weak 20 1

Question 43-12 : The function of the primer pump in a reciprocating engine is to ?

Provide additional fuel for an engine start.

Question 43-13 : One of the advantages of a turbocharger is ?

To make the power available less affected by altitude.

Question 43-14 : Assume an initial condition at a high cruise altitude with a constant speed propeller what will happen if the altitude is decreased while the throttle remains fully open and the waste gate is seized in the cruise position ?

The manifold absolute pressure map value may exceed the maximum allowed value.

With the engine producing power at low altitudes the turbocharger will be potentially over productive to prevent over boosting the wastegate will allow surplus exhaust energy to bypass the turbocharger at higher altitudes where the air is considerably less dense the wastegate will close off allowing the turbocharger to deliver the selected boostduring a descent from a high cruising altitude with the throttle fully open the turbocharger will be over productive and the manifold absolute pressure map value may exceed the maximum allowed value

Question 43-15 : If the engine with a fixed pitch propeller is detonating during climb out after takeoff the normal corrective action would be to ?

Reduce the throttle.

Question 43-16 : If when the magneto selector switch is set to the off position a piston engine continues to run normally the most probable cause is that ?

On a magneto the grounding wire is broken.

The ignition system provides the spark that ignites the fuelair mixture in the cylinders and is made up of magnetos spark plugs high tension leads and the ignition switch 901a magneto uses a permanent magnet to generate an electrical current completely independent of the aircraft's electrical system the magneto generates sufficiently high voltage to jump a spark across the spark plug gap in each cylinder the system begins to fire when you engage the starter and the crankshaft begins to turn it continues to operate whenever the crankshaft is rotatingmost standard certificated airplanes incorporate a dual ignition system with two individual magnetos separate sets of wires and spark plugs to increase reliability of the ignition system each magneto operates independently to fire one of the two spark plugs in each cylinder the firing of two spark plugs improves combustion of the fuelair mixture and results in a slightly higher power output if one of the magnetos fails the other is unaffected the engine will continue to operate normally although you can expect a slight decrease in engine power the same is true if one of the two spark plugs in a cylinder failsthe operation of the magneto is controlled in the cockpit by the ignition switch the switch has five positions 1 off2 r right3 l left4 both5 startwith right or left selected only the associated magneto is activated the system operates on both magnetos with both selectedyou can identify a malfunctioning ignition system during the pretakeoff check by observing the decrease in rpm that occurs when you first move the ignition switch from both to right and then from both to left a small decrease in engine rpm is normal during this check around 100 to 150 rpm if the engine stops running when you switch to one magneto or if the rpm drop exceeds the allowable limit do not fly the airplane until the problem is corrected the cause could be fouled plugs broken or shorted wires between the magneto and the plugs or improperly timed firing of the plugs it should be noted that 'no drop' in rpm is not normal and in that instance the airplane should not be flownfollowing engine shutdown turn the ignition switch to the off position even with the battery and master switches off the engine can fire and turn over if you leave the ignition switch on and the propeller is moved because the magneto requires no outside source of electrical power the potential for serious injury in this situation is obviousloose or broken wires in the ignition system also can cause problems for example if the ignition switch is off the magneto may continue to fire if the ignition switch ground wire is disconnected if this occurs the only way to stop the engine is to move the mixture lever to the idle cutoff position then have the system checked by a qualified aviation maintenance technician

Question 43-17 : Ignition occurs in each cylinder of a four stroke engine tdc = top dead centre ?

Before tdc at each second crankshaft revolution.

Question 43-18 : The lubricating system of an air cooled piston engine is used to ?

Reduce internal friction and provide cooling.

Question 43-19 : The first indication of carburettor icing in aeroplanes equipped with constant speed propellers during cruise would most likely be a ?

Decrease in manifold pressure.

On engines fitted with constant speed propellers a drop in power is indicated by a drop in manifold pressure the rpm remaining constant

Question 43-20 : The mixture control for a carburettor achieves its control by ?

Varying the fuel supply to the main discharge tube.

Question 43-21 : The mechanism to change the propeller blade angle of a small piston engine aeroplane in flight is operated ?

Hydraulically by engine oil.

Pdf656

Question 43-22 : The use of too low an octane fuel may cause ?

Detonation.

Question 43-23 : Which one of the following factors would be most likely to increase the possibility of detonation occurring within a piston engine ?

Using too lean a fuelair mixture.

Detonation is nothing less than a series of small explosions that take place within an engine's combustion chambers it can be extremely destructive breaking pistons rod bearings and anything else from the pistons down that a large hammer could damageweak airfuel mixtures can result in very uneven mixtures within the chamber uneven burning pressure spikes and detonation

Question 43-24 : Vents in oil tanks are primarily to ?

Prevent excessive pressure from building up in tank.

Question 43-25 : The cylinder head and oil temperatures may exceed their normal operating ranges if ?

A lower octane rating than specified for the engine is used.

Question 43-26 : When starting the engine or when the engine is running at idle rpm on the ground the mixture is ?

Question 43-27 : The cylinder head and oil temperature gauges are to exceed the normal operating ranges if a pilot ?

Uses fuel that has a rating lower than specified for the engine.

Question 43-28 : The lubricating system of an aircraft engine is used to ?

Aid in dissipation of heat.

Question 43-29 : On design purpose the relationship between the fuel octane rating and the maximum compression ratio of a piston engine is ?

The higher the octane rating is the higher the maximum compression ratio is.

Question 43-30 : A magnetic plug in an engine oil system can be used to ?

Collect ferrous particles.

The most basic type of magnetic filter is a drain plug where a magnet in the shape of a disc or cylinder is attached to its inside surface typically by adhesion periodically the magnetic plug is removed and inspected for ferromagnetic particles which are then wiped from the plug 902such plugs are commonly used in engine sumps gearboxes and occasionally in hydraulic reservoirs one useful advantage of mag plugs relates to examining the density of wear particles observed as a visual indication of the wear rate occurring within the machine over a fixed period of running time the appearance of these iron filings on magnets are often described in inspection reports using terms such as peach fuzz whiskers or christmas trees if one normally sees peach fuzz but on one occasion sees a christmas tree instead this would be a reportable condition requiring further inspection and remediation

Question 43-31 : Once the engine has started ignition systems of piston engines are ?

Independent of the electrical system of the aircraft.

Question 43-32 : The blade angle of a propeller is the angle between the ?

Reference chord line and the propeller plane of rotation.

Blade angle usually measured in degrees is the angle between the chord of the blade and the propeller plane of rotation 903

Question 43-33 : Assuming the same swept volume and no turbo charger diesel engines compared to petrol engines ?

Produce less maximum power output.

Question 43-34 : The operating principle of magnetos in a piston engine ignition system consists of ?

Breaking the primary circuit in order to induce a low amperage high voltage current which is distributed to the spark plugs.

Question 43-35 : In a four stroke piston engine the only 'driving' stroke is ?

Power.

Question 43-36 : Excessive priming of a piston engine should be avoided because 1 it drains the carburettor float chamber2 the risk of engine fire 3 the risk of flooding the engine4 it fouls the spark plugsthe combination that regroups all of the correct statements is ?

2 3 4.

A fuel primer is a small hand pump designed to put neat fuel directly into either the induction manifold near the combustion chamber or the inlet valve port before you start in the cold promote the presence of fuel vapour that will ignite to start the engineaside from the fire hazard excessive priming should be avoided because it fouls the spark plugs and there is a risk of flooding the engine

Question 43-37 : Which one of the following factors would be most likely to increase the possibility of detonation occurring within a piston engine ?

High cylinder head temperature.

Question 43-38 : The octane rating of a fuel characterises the ?

Resistance to detonation.

The octane rating of fuel is a measure of its performance in engines a higher octane number means that the fuel and air mixture can withstand more compression before detonating premature detonation can result in an engine making knocking pinging or rattling sounds high octane fuel therefore helps reduce or eliminate knocking pinging or rattling in engines

Question 43-39 : Both gas turbine and piston engines use a cycle made up of induction compression combustion and exhaust phases which of these statements about a piston engine are correct or incorrect i the process in a piston engine is intermittentii theoretically the combustion occurs at constant volume ?

I is correct ii is correct.

Piston engine the combustion process is intermittent governed by the rythm of the back and forth movements of the piston in a cylinder the combustion occurs at constant volume in the cylinderturbine engine the combustion process is continuous and occurs at constant pressure

Question 43-40 : When tas increases the blade angle of a constant speed propeller will rpm and throttle levers are not moved ?

Increase.

On a propeller the relative airflow is the resultant of the airflow due to rotation and to the forward speeda constant speed propeller automatically keeps the blade angle adjusted for maximum efficiency for most conditions encountered in flight so if tas or rpm change the blade angle will changethe blade angle 'pitch angle' if you prefer is a measurement of the distance between the propeller cord and the plane of rotation 905with an increasing tas the blade angle will increasea propeller is similar to a screw 906if we want to enter quicky in a material we need the black screw high pitch if we want to go slowly the metalic screw small pitch is more convenient 907an efficient propeller is one which has the least amount of slippage and therefore converts more engine horsepower into thrust a constant speed propeller keeps the propeller pitch adjusted for maximum efficiency for most conditions of flight