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Question 44-1 : With an aircraft fitted with a fixed pitch propeller, during flight at normal cruising speed, one magneto fails completely. this will first cause ? [ Attestation AIM ]
Loss of approximately 100 rpm.
Question 44-2 : 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 continuous..ii. theoretically the combustion occurs at constant pressure. ?
I is incorrect, ii is incorrect.
.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 cylinder...turbine engine the combustion process is continuous and occurs at constant pressure.
Question 44-3 : When excessively leaning the mixture for a better fuel economy, but still on the rich side of the peak egt, the following engine parameter s may exceed their normal operating ranges ?
Cylinder head and exhaust gas temperature.
Question 44-4 : 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 continuous..ii. theoretically the combustion occurs at constant volume. ?
I is incorrect, 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 cylinder...turbine engine the combustion process is continuous and occurs at constant pressure.
Question 44-5 : Given the following statements about diesel engines..1 power is set by the mixture control..2 there is no mixture control..3 the amount of power is determined by the fuel flow only..4 thermal efficiency is higher than that for a petrol engine..5 diesel fuel is more inflammable than petrol.. ?
2, 3, 4.
There is no mixture control and no throttle valve, the power output of a diesel engine is controlled by regulating the quantity of fuel that is injected into the cylinder the amount of air is constant. diesel engines are fitted with injectors, not with valves.
Question 44-6 : Diesel engines, compared to petrol engines have ?
A higher compression ratio.
Question 44-7 : The power output of a diesel engine without a turbo charger is regulated by ?
Fuel flow only.
On the gasoline engine, the speed and power output is regulated by limiting the air and fuel mixture entering the engine. the power output of a diesel engine is controlled by regulating the quantity of fuel that is injected into the cylinder the amount of air is constant.
Question 44-8 : The ignition system of a running piston engine receives electrical energy from ?
Rotating permanent magnets.
Question 44-9 : The purpose of magnetic chip detectors is to ?
Warn of impending failure.
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... 663..such 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 44-10 : Apart from flight into known icing conditions, the intake system of a diesel engine ?
Is never heated because a diesel engine is a injection engine.
Question 44-11 : The thermal efficiency of a diesel engine is higher than that of a petrol engine because ?
The compression ratio is much higher.
Question 44-12 : Given the following statements about diesel engines..1 power is regulated by the throttle valve..2 there is no throttle valve..3 power is set by the fuel flow..4 thermal efficiency is lower than that for a petrol engine..5 diesel fuel is less inflammable than petrol... ?
2, 3, 5.
There is no mixture control and no throttle valve, the power output of a diesel engine is controlled by regulating the quantity of fuel that is injected into the cylinder the amount of air is constant. diesel engines are fitted with injectors, not with valves.
Question 44-13 : In liquid cooled engines, the compostion by volume of coolant mixture is ?
30% ethylene glycol and 70% water.
Question 44-14 : The oil system for a piston engine incorporates an oil cooler that is fitted ?
In the return line to the oil tank after the oil has passed through the scavenge pump.
Question 44-15 : Diesel engines always produce a certain amount of soot, because ?
The fuel droplets coming from the atomiser do not burn completely.
Question 44-16 : What may happen during a continuous climb with a mixture setting fully rich ?
Fouling of spark plugs.
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.
Question 44-17 : Prolonged running at low rpm can have an adverse effect on the functioning of the ?
Spark plugs.
Question 44-18 : When leaning the mixture for the most economic cruise fuel flow, excessive leaning will cause ?
High cylinder head temperature.
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 your hand, no problem, but move it slowly and you will burn your hand slow burning lean mixtures will increase cht.
Question 44-19 : During climb with constant throttle and rpm lever setting mixture being constant the ?
Manifold absolute pressure map decreases.
The manifold absolute pressure map indicates the power output of a piston engine, being a measure of the pressure of the fuel/air mixture in the inlet manifold...in an unsupercharged engine, the reading will drop with height for a given throttle setting, because there is less atmospheric pressure to push the useful charge into the cylinder.
Question 44-20 : 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 intermittent..ii. theoretically the combustion occurs at constant pressure. ?
I is correct, ii is incorrect.
.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 cylinder...turbine engine the combustion process is continuous and occurs at constant pressure.
Question 44-21 : A piston engine compression ratio is the ratio of the ?
Total volume to the clearance volume.
Img897.compression ratio = volume at bottom dead total volume / volume at top dead clearance volume..the clearance volume is the volume that is not expelled from the cylinder.
Question 44-22 : The purpose of a chip detector in the oil system of an engine/gearbox is to indicate that ?
There are metal particles in the oil.
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....such 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 44-23 : The thermal efficiency of a piston engine is about... ?
30%.
Thermal efficiency is the ratio of useful work to the heat put in, expressed as a percentage...the first law of thermodynamics states that energy may be changed from one form to another, but cannot be destroyed. as far as engines are concerned, it means that heat and mechanical work are mutually convertible, and that the rate of exchande is constant and measurable...however, the second law says more or less that 'heat flows from a hot substance to a cold one unaided, but energy from an external source is needed for it to flow the other way'. that is, you might be able to convert most of your work into heat, but turning heat into work will incur serious losses, which is another way of saying that engines are grossly inefficient if it were otherwise, exhausts would be cold..in fact, engines waste as much energy in heat as the power they produce the approximate thermal efficiency of a four stroke engine is 30%.
Question 44-24 : On a normally aspirated engine non turbo charged , the manifold pressure gauge always indicates ?
A lower value than atmospheric pressure when the engine is running.
Devidson.if the engine is on full power i.e. the butterfly valve is fully open the admision pressure would be equal to the atmospheric pressure on a non turbo charged engine, no...no matter how wide the butterfly throttle is opened, there will always be some restriction, hence the manifold pressure will always be lower than atmospheric, even if only slightly.
Question 44-25 : The purpose of a distributor in an ignition system is to distribute ?
Secondary current to the sparking plugs.
.the purpose of the ignition system is to provide an ignition spark to the proper cylinder at the correct time in order to burn the compressed air/fuel mixture..it consists of two separate but closely related electrical circuits. low voltage primary circuit battery voltage.. high voltage secondary circuit over 20000 volts...the ignition coil is the unit that takes your relatively weak battery power and turns it into a spark powerful enough to ignite fuel vapor. inside a a traditional ignition coil are two coils of wire on top of each other. these coils are called windings. one winding is called the primary winding, the other is the secondary. the primary winding gets the juice together to make a spark and the secondary sends it out the door to the distributor...the distributor 'distributes' the secondary current to the sparking plugs.
Question 44-26 : Viscosity is ?
The tendency of a liquid or gas to resist flow.
Question 44-27 : With which instrument s do you monitor the power output of an aeroplane fitted with a fixed pitch propeller ?
Rpm indicator.
Question 44-28 : In a piston engine, turbocharger boost pressure may be monitored by ?
A manifold pressure gauge only.
Question 44-29 : Fixed pitch propellers are usually designed for maximum efficiency at ?
Cruising speed
Question 44-30 : Overheating of a piston engine is likely to result from an excessively ?
Weak mixture.
Jaredleto .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 your hand, no problem, but move it slowly and you will burn your hand slow burning lean mixtures will increase cht.
Question 44-31 : In an engine equipped with a float type carburettor, the low temperature that causes carburettor ice is normally the result of ?
Vaporization of fuel and expansion of the air in the carburettor.
One disadvantage of the float type carburetor is its icing tendency. the vaporization of fuel, combined with the expansion of air as it flows through the carburetor, causes a sudden cooling of the mixture. the temperature of the air passing through the carburetor may drop significantly within a fraction of a second. water vapor in the air is 'squeezed out' by this cooling and, if the temperature in the carburetor reaches 0°c or below, the moisture will be deposited as frost or ice inside the carburetor passages. even a slight accumulation of this deposit will reduce power and may lead to complete engine failure, particularly when the throttle is partly or fully closed.. 1048.the formation of carburetor ice may reduce or block fuel/air flow to the engine.
Question 44-32 : In addition to the fire hazard introduced, excessive priming should be avoided because ?
It fouls the spark plugs.
Question 44-33 : With respect to a piston engine aircraft, ice in the carburettor ?
May form at oat's higher than +10°c.
Question 44-34 : As the flight altitude increases, if no leaning is made with the mixture control ?
The density of air entering the carburettor decreases and the amount of fuel remains constant.
.density decreases as we gain altitude, but volume of air entering in the carburettor does not change, as for the volume of fuel fuel density does not change with altitude.
Question 44-35 : Cooling air for a reciprocating engine can be obtained by means of ?
Ram air
Question 44-36 : The main advantage of a constant speed propeller as compared to a fixed pitch propeller is a ?
High efficiency in a much wider speed range of the aeroplane.
.advantages of a constant speed propeller compared to a fixed pitch propeller.the power setting of a piston engine is defined by a combination of manifold pressure boost and rpm. where separate power lever and rpm lever control is provided, it is possible to vary one while leaving the other constant, so optimising the operation of the engine/propeller combination to give best efficiency/fuel economy and least engine wear and tear. in order to achieve this a 'variable pitch' propeller must be used enabling the pilot to select a propeller pitch and thus to vary rpm independently of manifold pressure, provided that the propeller is operating between its internal fine and coarse pitch stops. once an rpm has been selected, a control unit csu constant speed unit or pcu propeller control unit will automatically vary the propeller pitch angle and therefore its angle of attack to the prevailing relative airflow in order to maintain the selected rpm despite airspeed and manifold pressure variations. a constant speed propeller has a high efficiency in a much wider speed range than a fixed pitch propeller.
Question 44-37 : From the cruise, with all the parameters correctly set, if the altitude is reduced, to maintain the same mixture the fuel flow should ?
Increase.
.when altitude increases, air density decreases..to maintain a correct mixture ratio of 1 to 15 fuel mass / air mass if the altitude is reduced, we need to increase the fuel flow to maintain a constant ratio air volume entering the carburettor will not change, but the air mass will increase.
Question 44-38 : A turbocharger in a reciprocating engine consists of a ?
Compressor and turbine mounted on a common shaft.
Question 44-39 : An impulse coupling is inhibited at higher than normal rotational starting speeds by ?
Centrifugal force.
.impulse coupling magneto.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 magneto 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 centrifugal 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 44-40 : The very rapid magnetic field changes flux changes in the primary coil of a magneto are accomplished by the ?
Contact breaker points opening.
.inside the primary circuit is a set of contact points that make the flux reversals more abrupt when they open and close at critical moments..when the points are closed, current flows in the primary coil and a flux field builds up around it. when a spark is needed, they open, which causes the field in the primary to collapse and induce a current in the secondary winding as the field moves across it, which is fed to the spark plugs through the distributor...the more suddent the breaking of the primary circuit is, the more current will be induced in the secondary coil.
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