The purpose of magnetic chip detectors is to ?
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Apart from flight into known icing conditions the intake system of a diesel engine ?
The thermal efficiency of a diesel engine is higher than that of a petrol engine because ?
Given following statements about diesel engines 1 power regulated the throttle valve 2 there no throttle valve 3 power set the fuel flow 4 thermal efficiency lower than that a petrol engine 5 diesel fuel less inflammable than petrol the combination that regroups all of correct statements 2, 3, 5,, 2, 3,, 3, 5, 2, 4, 5. There no mixture control no throttle valve, power output of a diesel engine controlled regulating quantity of fuel that injected into cylinder (the amount of air constant). diesel engines are fitted with injectors, not with valves. 
In liquid cooled engines compostion volume of coolant mixture 3 % ethylene glycol 7 % water, 6 % ethylene glycol 4 % water, 5 % ethylene glycol 5 % water, 65% ethylene glycol 35% water. 
The oil system a piston engine incorporates an oil cooler that fitted In return line to oil tank after oil has passed through scavenge pump, after pressure pump but before oil passes through engine, after oil has passed through engine before it enters sump, between oil tank the pressure pump. 
Diesel engines always produce a certain amount of soot because The fuel droplets coming from atomiser do not burn completely, mixture always too rich, intake air too cold, fuel droplets are too small. Question Turbine Engines 30 Answer 8
What may happen during a continuous climb with a mixture setting fully rich Fouling of spark plugs, increase of power available, the engine will operate smoother even though fuel consumption increased, the engine will overheat. Carburetors are calibrated to operate with mixture control set to 'full rich' when operating at sea level. as aircraft gains altitude it becomes necessary to reduce amount of fuel entering carburetor, because amount of air automatically decreasing with altitude, due to lower atmospheric pressure. if pilot fails to decrease amount of fuel as altitude gained, result will be an overly 'rich' mixture, creating problems such as fouled spark plugs excessive fuel consumption. Question Turbine Engines 30 Answer 9
Prolonged running at low rpm can have an adverse effect on functioning of Spark plugs, carburettor, oil pump, fuel filter. Question Turbine Engines 30 Answer 10
When leaning mixture the most economic cruise fuel flow excessive leaning will cause High cylinder head temperature, high engine rpm, low cylinder head temperature, high manifold pressure. Egt relative to temperature of charge as it burns within cylinder. cht measures temperature of engine cylinder. the highest egt achieved at a ratio of 15 parts of air to one part of fuel. if ratio reduced ie rich charge temperature reduces due to excess fuel being left in cylinder. if ratio greater than 15 1 ie lean or weak charge cooled excess air. to appreciate why cht increases with lean mixtures we must consider speed at which fuel burns, ie its flame rate. lean mixtures burn slower than rich mixtures. this means more heat transferred to engine components with lean mixtures. example. if you move a lighted match quickly under your hand, no problem, but move it slowly you will burn your hand! slow burning lean mixtures will increase cht. Question Turbine Engines 30 Answer 11
During climb with constant throttle and rpm lever setting mixture being constant Manifold absolute pressure (map) decreases, rpm decreases, manifold absolute pressure (map) increases, rpm increases. The manifold absolute pressure (map) indicates power output of a piston engine, being a measure of pressure of fuel/air mixture in inlet manifold. in an unsupercharged engine, reading will drop with height a given throttle setting, because there less atmospheric pressure to push useful charge into cylinder. Question Turbine Engines 30 Answer 12
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 intermittent ii theoretically combustion occurs at constant pressure I correct, ii incorrect, i incorrect, ii incorrect, i incorrect, ii correct, i correct, ii correct. piston engine combustion process intermittent, governed the rythm of back forth movements of piston in a cylinder. the combustion occurs at constant volume in cylinder. turbine engine combustion process continuous occurs at constant pressure. Question Turbine Engines 30 Answer 13
A piston engine compression ratio the ratio of Total volume to clearance volume, clearance volume to swept volume, total volume to swept volume, swept volume to clearance volume. compression ratio = volume at bottom dead (total volume) / volume at top dead (clearance volume) the clearance volume the volume that not expelled from cylinder. Question Turbine Engines 30 Answer 14
The purpose of a chip detector in oil system of an engine/gearbox to indicate that There are metal particles in oil, piston rings are worn, seals are worn, oil temperature too high. The most basic type of magnetic filter a drain plug, where a magnet in shape of a disc or cylinder attached to its inside surface (typically adhesion). periodically, magnetic plug removed inspected ferromagnetic particles, which are then wiped from plug. such plugs are commonly used in engine sumps, gearboxes occasionally in hydraulic reservoirs. one useful advantage of mag plugs relates to examining density of wear particles observed as a visual indication of wear rate occurring within 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 remediation. Question Turbine Engines 30 Answer 15
The thermal efficiency of a piston engine about Thermal efficiency the ratio of useful work to 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 mechanical work are mutually convertible, that rate of exchande constant measurable. however, second law says (more or less) that 'heat flows from a hot substance to a cold one unaided, but energy from an external source needed it to flow 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 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 power they produce approximate thermal efficiency of a four stroke engine 30%. Question Turbine Engines 30 Answer 16
On a normally aspirated engine non turbo charged manifold pressure gauge always indicates A lower value than atmospheric pressure when engine running, a value equal to qfe when engine at full power on ground, a greater value than atmospheric pressure when engine running, zero on ground when engine stopped. devidson if engine on full power (i.e. butterfly valve fully open) admision pressure would be equal to atmospheric pressure on a non turbo charged engine, no ? no matter how wide butterfly throttle opened, there will always be some restriction, hence manifold pressure will always be lower than atmospheric, even if only slightly. Question Turbine Engines 30 Answer 17
The purpose of a distributor in an ignition system to distribute Secondary current to sparking plugs, primary current to condenser, secondary current to condenser, primary current to sparking plugs. the purpose of ignition system to provide an ignition spark to proper cylinder at correct time in order to burn 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 the unit that takes your relatively weak battery power 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 called primary winding, other the secondary. the primary winding gets juice together to make a spark the secondary sends it out door to distributor. the distributor 'distribute secondary current to sparking plugs. Question Turbine Engines 30 Answer 18
Viscosity is The tendency of a liquid or gas to resist flow, temperature dependence of an oil, pressure resistance of an oil, flow velocity inside oil lines. Question Turbine Engines 30 Answer 19
With which instrument s do you monitor power output of an aeroplane fitted with a fixed pitch propeller Rpm indicator, fuel flow indicator, rpm map indicator, cylinder head temperature indicator. Question Turbine Engines 30 Answer 20
In a piston engine turbocharger boost pressure may be monitored A manifold pressure gauge only, a cylinder head temperature gauge (cht), a manifold pressure gauge, engine rpm readings, both a cht gauge manifold pressure gauge, both engine rpm readings a manifold pressure gauge. Question Turbine Engines 30 Answer 21
Fixed pitch propellers are usually designed maximum efficiency at Cruising speed, idling, full throttle, take off Question Turbine Engines 30 Answer 22
Overheating of a piston engine likely to result from an excessively Weak mixture, rich mixture, low barometric pressure, high barometric pressure. Jaredleto egt relative to temperature of charge as it burns within cylinder. cht measures temperature of engine cylinder. the highest egt achieved at a ratio of 15 parts of air to one part of fuel. if ratio reduced ie rich charge temperature reduces due to excess fuel being left in cylinder. if ratio greater than 15 1 ie lean or weak charge cooled excess air. to appreciate why cht increases with lean mixtures we must consider speed at which fuel burns, ie its flame rate. lean mixtures burn slower than rich mixtures. this means more heat transferred to engine components with lean mixtures. example. if you move a lighted match quickly under your hand, no problem, but move it slowly you will burn your hand! slow burning lean mixtures will increase cht. Question Turbine Engines 30 Answer 23
In an engine equipped with a float type carburettor low temperature that causes carburettor ice normally result of Vaporization of fuel expansion of air in carburettor, freezing temperature of air entering carburettor, compression of air at carburettor venturi, low volatility of aviation fuel. One disadvantage of float type carburetor its icing tendency. the vaporization of fuel, combined with expansion of air as it flows through carburetor, causes a sudden cooling of mixture. the temperature of air passing through carburetor may drop significantly within a fraction of a second. water vapor in air 'squeezed out' this cooling and, if temperature in carburetor reaches 0°c or below, moisture will be deposited as frost or ice inside carburetor passages. even a slight accumulation of this deposit will reduce power may lead to complete engine failure, particularly when throttle partly or fully closed. the formation of carburetor ice may reduce or block fuel/air flow to engine. Question Turbine Engines 30 Answer 24
In addition to fire hazard introduced excessive priming should be avoided because It fouls spark plugs, it washes lubricant of cylinder walls, it drains carburettor float chamber, gasoline dilutes oil necessitates changing oil. Question Turbine Engines 30 Answer 25
With respect to a piston engine aircraft ice in carburettor May form at oat's higher than +°c, will only form at oat's below +°c, will only form at outside air temperatures (oat's) below freezing point of water, will only form at oat's below freezing point of fuel. Question Turbine Engines 30 Answer 26
As flight altitude increases if no leaning made with mixture control The density of air entering carburettor decreases the amount of fuel remains constant, volume of air entering carburettor remains constant the amount of fuel decreases, volume of air entering carburettor decreases the amount of fuel decreases, density of air entering carburettor decreases the amount of fuel increases. density decreases as we gain altitude, but volume of air entering in carburettor does not change, as the volume of fuel (fuel density does not change with altitude). Question Turbine Engines 30 Answer 27
Cooling air a reciprocating engine can be obtained means of Ram air, a supercharger, a turbocharger, a pneumatic system. Question Turbine Engines 30 Answer 28
The main advantage of a constant speed propeller as compared to a fixed pitch propeller a High efficiency in a much wider speed range of aeroplane, constant efficiency in whole speed range of aeroplane, lower propeller blade stress, higher efficiency in cruising range. advantages of a constant speed propeller compared to a fixed pitch propeller the power setting of a piston engine defined a combination of manifold pressure (boost) rpm. where separate power lever rpm lever control provided, it possible to vary one while leaving other constant, so optimising operation of engine/propeller combination to give best efficiency/fuel economy least engine wear tear. in order to achieve this a 'variable pitch' propeller must be used enabling pilot to select a propeller pitch thus to vary rpm independently of manifold pressure, provided that propeller operating between its internal fine coarse pitch stops. once an rpm has been selected, a control unit (csu constant speed unit or pcu propeller control unit) will automatically vary propeller pitch angle therefore its angle of attack to prevailing relative airflow in order to maintain selected rpm despite airspeed manifold pressure variations. a constant speed propeller has a high efficiency in a much wider speed range than a fixed pitch propeller. Question Turbine Engines 30 Answer 29
From cruise with all parameters correctly set if altitude reduced to maintain same mixture fuel flow should Increase, decrease, remain same, increase or decrease, depending on engine type. when altitude increases, air density decreases. to maintain a correct mixture ratio of 1 to 15 (fuel mass / air mass) if altitude reduced, we need to increase fuel flow to maintain a constant ratio (air volume entering carburettor will not change, but air mass will increase). Question Turbine Engines 30 Answer 30
A turbocharger in a reciprocating engine consists of a Compressor turbine mounted on a common shaft, compressor turbine on individual shafts, compressor driving a turbine via a reduction gear, turbine driving a compressor via a reduction gear. Question Turbine Engines 30 Answer 31
An impulse coupling inhibited at higher than normal rotational starting speeds Centrifugal force, engine oil pressure, a coil spring, electro magnetic action of operating magneto. impulse coupling magneto the impulse coupling a spring loaded mechanical coupling which delays rotation of magneto during an engine start. after a short period of rotation device allows magneto to catch up, in effect spinning magneto shaft faster than engine turning it. the faster it turns, hotter spark the bigger voltage impulse, making easier starting. after engine running centrifugal forces move spring loaded arms, which make impulse coupling work at low speeds, out of way. the impulse coupling only works at very low engine speeds. Question Turbine Engines 30 Answer 32
The very rapid magnetic field changes flux changes in primary coil of a magneto are accomplished the Contact breaker points opening, distributor arm aligning with one of high voltage segments, contact breaker points closing, rotor turning past position of maximum flux in armature. inside primary circuit a set of contact points that make flux reversals more abrupt when they open close at critical moments. when points are closed, current flows in primary coil a flux field builds up around it. when a spark needed, they open, which causes field in primary to collapse induce a current in secondary winding as field moves across it, which fed to spark plugs through distributor. the more suddent breaking of primary circuit is, more current will be induced in secondary coil. Question Turbine Engines 30 Answer 33
In a compressor stage of a jet engine sequence Rotor stator, stator rotor, rotor rotor stator, stator stator rotor Compr es sor highlighted rs means correct order, so rotor stator turbine stage opposite. Question Turbine Engines 30 Answer 34
The accessory units driven the accessory gearbox of a turbo jet engine are 1 thrust reverser pneumatic motors2 ac generator through its constant speed drive csd 3 oil pumps4 hydraulic pumps5 high pressure fuel pumpsthe combination regrouping all correct statements 2, 3, 4, 5,, 2, 3, 4, 5, 2, 3, 4,, 2, 3, 4. the accessory gearbox driven a radial shaft that meshes with a bevel gear driven the n2 (or gas producer rotor), is used to drive essential engine components such as fuel pump, oil pump, fuel control unit, generators hydraulic pumps. the accessory gear box also used to drive engine rpm feedback tacho generators, is means which starter drives engine. these are systems which must operate as soon as engine starts. structure containing gearbox can be utilised as a support as well. each component that attaches to accesssory gearbox has its own mounting pad with its unique gear reduction speed rotational direction. Question Turbine Engines 30 Answer 35
Consider a jet engine whose control based on engine pressure ratio epr 1 with a constant epr thrust decreases when altitude increases2 with a constant epr thrust independent of mach number3 at same environmental conditions a given epr setting maintains thrust irrespective of engine wear due to ageing 4 epr determined the impact pressure difference between turbine outlet and compressor inlet5 on take off in event of icing not detected the crew indicated epr lower than real eprthe combination regrouping all correct statements , 3, 3, 4, 5,, 5, 2, 3, 4. Engine pressure ratio (epr) a measure of thrust of a jet engine obtained dividing pressure at back of engine the pressure at front. epr settings vary with altitude temperature. when altitude increases, thrust decreases. answer 4 the epr determined the impact pressure difference between turbine outlet the compressor inlet wrong, this a ratio, not a difference. Question Turbine Engines 30 Answer 36
In axial flow compressor of a turbo jet engine flow duct tapered its shape calculated so as to Maintain a constant axial speed in cruising flight, maintain a constant axial speed whatever engine rating, reduce axial speed in cruising flight, reduce axial speed, whatever engine rating. The duct in question the convergent duct formed between compressor engine compressor casing. the airflow through a jet engine varies dependant on thrust selection, since engine runs most of time at cruise, engine designed to give correct flow rates at this thrust setting. Question Turbine Engines 30 Answer 37
In stator of a turbine gas velocity v and static pressure ps vary as follows V increases, ps decreases, v increases, ps increases, v decreases, ps increases, v decreases, ps decreases. If you have multiple stage turbines there a set of guide vanes between each turbine disc to redirect flow again before next turbine blade. they are stationary so are sometimes called stators. with turbine you want a high velocity, so turbine blades are designed to extract power from hot expanding gasses to turn compressor, using high velocity hitting turbine blade. the guide vanes straighten flow before next set of turbine blades, but in effect it decreases pressure increases velocity. this also prevents excessive backpressure which could work its way forward affect combustion process. the compressor on other hand designed to increase pressure through each of stages, so you can deliver a good mass flow to combustion chambers. however increasing pressure will try to reverse flow, so convergent duct designed to keep velocity constant through whole compressor, so that momentum of airflow prevents reverse flow. in effect velocity therefore increased in each rotor section. velocity increases decreases through each set of rotors stators, by using a convergent duct velocity therefore stays constant, but pressure steadily increasing through each stage. Question Turbine Engines 30 Answer 38
Epr can be defined as ratio of The total turbine outlet pressure to total compressor inlet pressure, total turbine outlet pressure to total compressor outlet pressure , total turbine inlet pressure to total compressor outlet pressure, total turbine inlet pressure to total compressor inlet pressure. Question Turbine Engines 30 Answer 39
A gas turbine engine turbine section may employ active clearance control To provide enhanced clearances between blade tips the casing, in order to cool disc, in order to reduce 'creep' in blades, as a method of attaching stators rotors to hub of disc. active clearance control (acc) a method used in gas turbines to improve fuel efficiency. this achieved controlling tip clearance. it particularly effective on turbofans since they are required to respond quickly to changes of thrust setting. the active clearance control consists of acc valve which receives air from bypass duct routes air to flow over pipes surrounding turbine casing which in turn reduces thermal expansion of turbine case maintains accurate clearance between turbine case the blade tip. this clearance should be maintained accurately which essential the engine efficiency its performance. the acc valve opening adjusted automatically the fadec system depending on throttle position. Question Turbine Engines 30 Answer 40
In a gas turbine engine maximum gas temperature attained Within combustion chamber, at turbine entrance, in cooling airflow around flame tube, at entry to exhaust unit.
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