Registration > lift > off : Which of these statements about compressor stall are correct or incorrect.i a ?

Question 34-1 : I is correct ii is correct i is correct ii is incorrect i is incorrect ii is correct i is incorrect ii is incorrect

exemple 134 i is correct, ii is correct. — Like the stall of a wing compressor stall is caused by a breakdown of airflow .if your wing is suitable for high speed and you fly at low speed and large angle of attack the stall is most likely to occur.a compressor stall is most likely to occur when the air flow stagnates in the rear stages of the compressor a compressor blade is hitting the oncoming airflow at an angle of attack that is determined by a combination of the rotational speed and the incoming airflow .when the incoming speed is low the angle of attack will be high when the angle of attack gets too high the blade stalls so when the axial flow in a compressor backs up the blades stall pressure increase in the rear stages this slows down the flow .you can prevent this by dumping some late stage air to atmosphere via bleed valves i is correct, ii is correct.

In a compressor stage if the axial air velocity increases more than the rotor ?

Question 34-2 : Stall margin increases stall margin decreases pressure ratio will be too high relative air velocity becomes supersonic

exemple 138 stall margin increases. — .compressor stall occurs when the compressor sucks too much air for the turbine wheels to handle excessive pressure then builds aft of the compressor and the compressor blades stall .a compressor blade is hitting the oncoming airflow at an angle of attack that is determined by a combination of the rotational speed and the incoming airflow .when the incoming air flow speed is high the blade angle of attack will be low the stall margin increases there is less risk to encounter a compressor stall stall margin increases.

Which of these statements about compressor stall are correct or incorrect.i a ?

Question 34-3 : I is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is incorrect i is correct ii is correct

exemple 142 i is incorrect, ii is correct. — Like the stall of a wing compressor stall is caused by a breakdown of airflow .if your wing is suitable for high speed and you fly at low speed and large angle of attack the stall is most likely to occur.a compressor stall is most likely to occur when the air flow stagnates in the rear stages of the compressor a compressor blade is hitting the oncoming airflow at an angle of attack that is determined by a combination of the rotational speed and the incoming airflow .when the incoming speed is low the angle of attack will be high when the angle of attack gets too high the blade stalls so when the axial flow in a compressor backs up the blades stall pressure increase in the rear stages this slows down the flow .you can prevent this by dumping some late stage air to atmosphere via bleed valves i is incorrect, ii is correct.

With regard to a twin spool turbofan an abortive start hung start will result in ?

Question 34-4 : N2 speed stabilising at a lower than normal rpm and a subsequent increase in egt n2 speed stabilising at a higher than normal rpm and a subsequent increase in egt n2 speed stabilising at a lower than normal rpm and a subsequent decrease in egt n2 speed stabilising at a higher than normal rpm and a subsequent decrease in egt

exemple 146 n2 speed stabilising at a lower than normal rpm and a subsequent increase in egt. — .after the normal light up sequence until the starter 'cut out' a hung start is identified by light off followed by abnormally slow acceleration and rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start is associated with low fuel flow and proportionally low egt a rich condition can be recognized by a high fuel flow and an egt rise which may tend to develop into an over temperature condition and possible compressor stall..hung starts may be caused by. starter air pressure too low to accelerate engine to self sustaining speed.. premature starter deactivation. fod foreign object debris to compressor. faulty pressurizing valves not opening at scheduled fuel pressure setting. incorrect scheduling of hp compressor igv and variable stators. turbine section damage n2 speed stabilising at a lower than normal rpm and a subsequent increase in egt.

Which of the following statements is correct about the flow in a divergent ?

Question 34-5 : I is incorrect ii is correct i is correct ii is incorrect i is correct ii is correct i is incorrect ii is incorrect

exemple 150 i is incorrect, ii is correct. — i is incorrect, ii is correct.

One of the functions of a gas turbine engine subsonic intake is to ?

Question 34-6 : Decrease airflow velocity increase total pressure increase airflow velocity decrease static temperature

exemple 154 decrease airflow velocity. — decrease airflow velocity.

One of the advantages of multiple spool jet engine designs is that ?

Question 34-7 : A smaller air starter driving only a single spool can be used if one spool seizes the remaining spool s will continue to operate normally a compressor stall cannot occur under any condition engine length can be reduced

exemple 158 a smaller air starter driving only a single spool can be used. — .the air starter motor is possibly the most popular starting system presently in use it is light simple to use and very economical utilizing low pressure air the air starter motor is fastened to the accessory gearbox of the engine the sources of air available for engine start in order of preference they are the aircraft apu. the ground power unit. a cross bleed start where air from an already started engine is used .air from one of these sources is fed through an electrically controlled start valve to the air inlet to rotate the turbine rotor and is then exhausted .on a multiple spool jet engine a small air starter motor can drive a single spool which when started permits to start the other spools a smaller air starter driving only a single spool can be used.

Which of these statements about compressor stall are correct or incorrect.i a ?

Question 34-8 : I is incorrect ii is incorrect i is correct ii is incorrect i is incorrect ii is correct i is correct ii is correct

exemple 162 i is incorrect, ii is incorrect. — Like the stall of a wing compressor stall is caused by a breakdown of airflow .if your wing is suitable for high speed and you fly at low speed and large angle of attack the stall is most likely to occur.a compressor stall is most likely to occur when the air flow stagnates in the rear stages of the compressor a compressor blade is hitting the oncoming airflow at an angle of attack that is determined by a combination of the rotational speed and the incoming airflow .when the incoming speed is low the angle of attack will be high when the angle of attack gets too high the blade stalls so when the axial flow in a compressor backs up the blades stall pressure increase in the rear stages this slows down the flow .you can prevent this by dumping some late stage air to atmosphere via bleed valves i is incorrect, ii is incorrect.

After a successful start of a high bypass turbofan engine the air starter ?

Question 34-9 : Is disengaged by the coupling between engine n2 spool and starter by the use of centrifugal forces is disengaged by using a clutch that is controlled by the main engine control is disengaged by the coupling between engine n1 spool and starter by the use of centrifugal forces remains engaged and rotates continuously with the n2 spool

exemple 166 is disengaged by the coupling between engine n2 spool and starter by the use of centrifugal forces. — Air starting is used on most commercial and some military jet engines it has many advantages over other starting systems and is comparatively light simple and economical to operate 10 an air starter motor transmits power through a reduction gear and clutch to the starter output shaft which is connected to the engine.the starter turbine is rotated by air taken from an external ground supply an auxiliary power unit a p u or as a cross feed from a running engine the air supply to the starter is controlled by an elec trically operated control and pressure reducing valve that is opened when an engine start is selected and is automatically closed at a predetermined starter speed the clutch also automatically disengages as the engine accelerates up to idling rpm and the rotation of the starter ceases is disengaged by the coupling between engine n2 spool and starter by the use of centrifugal forces.

Both gas turbine and piston engines use a cycle made up of induction ?

Question 34-10 : I is correct ii is incorrect i is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is correct

exemple 170 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 i is correct, ii is incorrect.

Which of these statements about compressor stall are correct or incorrect.i a ?

Question 34-11 : I is correct ii is incorrect i is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is correct

exemple 174 i is correct, ii is incorrect. — Like the stall of a wing compressor stall is caused by a breakdown of airflow .if your wing is suitable for high speed and you fly at low speed and large angle of attack the stall is most likely to occur.a compressor stall is most likely to occur when the air flow stagnates in the rear stages of the compressor a compressor blade is hitting the oncoming airflow at an angle of attack that is determined by a combination of the rotational speed and the incoming airflow .when the incoming speed is low the angle of attack will be high when the angle of attack gets too high the blade stalls so when the axial flow in a compressor backs up the blades stall pressure increase in the rear stages this slows down the flow .you can prevent this by dumping some late stage air to atmosphere via bleed valves i is correct, ii is incorrect.

The following problems may occur when starting a twin spool turbofan engine ?

Question 34-12 : No n1 rotation although n2 may accelerate normally no n2 rotation although n1 may accelerate normally a hung abortive start with no light up indication after 'fuel on' selection a hung abortive start with fuel flow indication zero after 'fuel on' selection

exemple 178 no n1 rotation, although n2 may accelerate normally. — .during engine start the compressor is very inefficient if the engine experiences more than the usual difficulty accelerating due to such problems as early starter cut out fuel mis scheduling or strong tailwinds the engine may spend a considerable time at very low rpm sub idle normal engine cooling flows will not be effective during sub idle operation and turbine temperatures may appear relatively high this is known as a hot start no n1 rotation, although n2 may accelerate normally.

Both gas turbine and piston engines use a cycle made up of induction ?

Question 34-13 : I is incorrect ii is correct i is incorrect ii is incorrect i is correct ii is correct 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

The most unfavourable conditions for adequate inlet air flow of a turbofan ?

Question 34-14 : Maximum take off thrust zero forward speed and strong crosswind conditions maximum thrust during climb out with strong crosswind idle thrust zero forward speed with no wind maximum thrust at rotation speed on the ground during take off

exemple 186 maximum take-off thrust, zero forward speed and strong crosswind conditions. — maximum take-off thrust, zero forward speed and strong crosswind conditions.

If a twin spool gas turbine engine is controlled by a conventional n2 control ?

Question 34-15 : Overspeed of the lp turbine n2 and epr increase n1 and n2 increase n1 decrease and epr increase

In a twin spool engine the lp turbine is connected to the lp compressor the hp turbine is connected to the hp compressor the lp turbine drives the lp compressor if a rupture occurs it may result in an overspeed of the lp turbine

The rotor blades of an axial compressor of a gas turbine engine are often ?

Question 34-16 : Limits damage to the blades due to vibration limits fod damage limits damage due to creep facilitates easy assembly and removal

exemple 194 limits damage to the blades due to vibration. — limits damage to the blades due to vibration.

For a turbine engine the self sustaining speed relates to the minimum rpm at ?

Question 34-17 : Will continue to operate without any starter motor assistance is designed to idle after starting operates most efficiently in the cruise will enable the generators to supply bus bar voltage

exemple 198 will continue to operate without any starter motor assistance. — will continue to operate without any starter motor assistance.

The primary function of the diffuser located between the compressor and the ?

Question 34-18 : Decrease the flow velocity increase total pressure convert kinetic energy into mechanical energy increase the temperature of the compressed air

exemple 202 decrease the flow velocity. — Before combustion can proceed the air velocity must be greatly reduced .air leaves the compressor through exit guide vanes which convert the radial component of the air flow out of the compressor to straight line flow the air then enters the diffuser section of the engine which is a very divergent duct the primary function of the diffuser structure is aerodynamic the divergent duct shape converts most of the air's velocity pi into static pressure ps as a result the highest static pressure and lowest velocity in the entire engine is at the point of diffuser discharge and combustor inlet other aerodynamic design considerations that are important in the diffuser section arise from the need for a short flow path uniform flow distribution and low drag loss decrease the flow velocity.

A fadec on a gas turbine engine ?

Question 34-19 : Is single fault tolerant is a single channel system is a three channel system consists of two identical channels cross linked through an non engine related aircraft computer

exemple 206 is single fault tolerant. — Single input data failure will not affect the normal operation a 'full authority digital engine control' is single fault tolerant .a fadec is an engine control system in which the primary functions use digital electronics and the electronic engine control eec unit has full range authority over the engine power or thrust is single fault tolerant.

When a turbo prop aeroplane decelerates during the intial part of the landing ?

Question 34-20 : Produces negative thrust produces zero thrust is feathered produces positive thrust

exemple 210 produces negative thrust. — produces negative thrust.

Most high bypass unmixed turbofan engines are equipped with a cold exhaust ?

Question 34-21 : Save costs and mass at the expense of a reduction in available reverse thrust prevent disturbance of cold exhaust reversed airflow by the hot exhaust reversed gas flow reduce the risk of exhaust gas re ingestion prevent extra fuel consumption due to operation of the hot exhaust reverser turbine reverser

exemple 214 save costs and mass at the expense of a reduction in available reverse thrust. — High bypass turbofan engines are equipped with a cold exhaust reverser only in order to save costs and mass .it is not impossible to reverse the hot exhaust gas but it is complex the gain in reverse thrust will be less than 20% for an increase in maintenance costs and a higher inflight consumption due to weight of the system. typical high bypass thrust reversers . 1052 save costs and mass at the expense of a reduction in available reverse thrust.

A booster or lp compressor in a twin spool turbofan ?

Question 34-22 : Rotates at the same rotor speed as the fan rotates at the same rotor speed as the hp turbine rotates at a rotor speed different from both fan hp compressor and hp turbine rotates at the same rotor speed as the hp compressor

exemple 218 rotates at the same rotor speed as the fan. — If the engine is a twin spool turbofan it is highly likely that there will be a hp compressor lp compressor and a fan the lp comp and the fan will be driven from the same turbine on the same shaft and will therefore be at the same speed. 948 rotates at the same rotor speed as the fan.

The function of the swirl vanes round the fuel nozzles is to.1 increase air ?

Question 34-23 : 2 3 1 2 1 2 3 1 only

The take off of a jet aeroplane may be performed with 'reduced thrust' in order ?

Question 34-24 : Reduce maintenance costs save fuel reduce take off noise reduce the risk of engine failure during take off

exemple 226 reduce maintenance costs. — reduce maintenance costs.

In an ignition system during a normal start of a gas turbine engine igniter ?

Question 34-25 : Should commence prior to fuel entering the combustion chamber should commence after fuel has entered the combustion chamber should commence prior to starter motor engagement to prevent a hot start commences upon starter motor engagement and is deactivated at a rotor speed of approximately 15% below idle rpm

exemple 230 should commence prior to fuel entering the combustion chamber. — should commence prior to fuel entering the combustion chamber.

A gas turbine engine is run at ground idle for a period of time prior to ?

Question 34-26 : Prevent seizure of the rotor blades in their seals prevent vapour lock in the fuel control and/or fuel lines prevent seizure of the engine bearings allow the engine oil to cool

exemple 234 prevent seizure of the rotor blades in their seals. — This allows to the gas generator and the power turbine discs more time to cool than if the engines were immediately shut down the danger is that the rotor will cool and will shrink more rapidly than the blades and they could be seized in their seals prevent seizure of the rotor blades in their seals.

The purpose of variable by pass valves in a high bypass turbofan engine between ?

Question 34-27 : Prevent fan stall and lp compressor stall during engine start and low rotor speeds provide sufficient air to the hp compressor during engine start prevent fan surge at high rotor speeds high rpm prevent hp compressor stall during engine start

exemple 238 prevent fan stall and lp compressor stall during engine start and low rotor speeds. — A bypass valve is another name for a bleed valve it can also be called a blow off valve anti stall valve or an acceleration valve prevent fan stall and lp compressor stall during engine start and low rotor speeds.

If a gas turbine engine fuel/oil heat exchanger is located downstream of the hp ?

Question 34-28 : Rise rise and the fuel nozzles eventually to become clogged fall fall and the oil jets eventually to become clogged

The oil in the fuel/oil heat exchanger located in the tanks is always at a higher pressure than the fuel but the question states located downstream of the hp fuel pump so it is a secondary fuel/oil heat exchanger in order to avoid fuel icing in the fuel regulation system. in this heat exchanger you will have high pressure fuel and relatively low pressure oil so any internal leak will transfer fuel to the oil system raising the indicated oil level

The compressor pressure ratio of an axial flow compressor is primarily ?

Question 34-29 : Number of stages rotor diameter compressor inlet temperature design value compressor inlet pressure design value

exemple 246 number of stages. — number of stages.

In a theoretical gas turbine cycle combustion takes place at constant ?

Question 34-30 : Pressure energy temperature volume

When a gas turbine engine accelerates from idle to take off thrust and the ?

Question 34-31 : A compressor stall stagnation supersonic airflow at the compressor blade trailing edges a compressor blade airflow angle of attack that is too small

exemple 254 a compressor stall. — Like the stall of a wing compressor stall is caused by a breakdown of airflow .a compressor stall is most likely to occur when the air flow stagnates in the rear stages of the compressor a compressor blade is hitting the oncoming airflow at an angle of attack that is determined by a combination of the rotational speed and the incoming airflow .when the incoming speed is low the angle of attack will be high when the angle of attack gets too high the blade stalls so when the axial flow in a compressor backs up the blades stall pressure increase in the rear stages this slows down the flow .you can prevent this by dumping some late stage air to atmosphere via bleed valves a compressor stall.

Which of the following parameters remains constant in a divergent subsonic gas ?

Question 34-32 : Total temperature static pressure dynamic pressure static temperature

exemple 258 total temperature. — total temperature.

The most favourable conditions to apply the flexible take off procedure are .1 ?

Question 34-33 : 2 4 5 1 3 5 2 3 6 2 4 6

Assuming the jet pipe is not choked the equation to calculate jet engine thrust ?

Question 34-34 : T = m vj vv t = m vv vj t = m vv + vj t = mvj

exemple 266 t = m(vj - vv) — t = m(vj - vv)

Given . p0 = static ambient pressure .t0 = static ambient temperature.m = air ?

Question 34-35 : T = m vj vv + a pj p0 t = m vv vj + a t j t0 t = m vv vj + a pj p0 t = m vj vv + a tj t0

exemple 270 t = m(vj -vv ) + a(pj - p0). — Thrust = air mass flow jet exhaust velocity true air speed + exhaust cross sectional area jet exhaust static pressure static ambient pressure.thrust is equal to the change in momentum of the air entering and leaving it is measured by the acceleration of the air through the engine t = m(vj -vv ) + a(pj - p0).

The axial compressor of a gas turbine engine usually has more stages than its ?

Question 34-36 : The power output of a turbine stage is higher than the power consumption of a compressor stage the compressor consumes much more power than the turbine bleed air is taken from the compressor turbine speed is much higher than compressor speed

exemple 274 the power output of a turbine stage is higher than the power consumption of a compressor stage. — the power output of a turbine stage is higher than the power consumption of a compressor stage.

On a fadec gas turbine engine during normal flight the power for the fadec's ?

Question 34-37 : The fadec power source s on the engine the aircraft battery the aircraft generator the apu generator

exemple 278 the fadec power source(s) on the engine. — The fadec has its own independent power supply generator which is separate from the aircraft generator to ensure that the fadec system has electrical power as long as the engine is running regardless of any problems or faults with the aircraft system the fadec power source(s) on the engine.

In a gas turbine combustion chamber ?

Question 34-38 : Secondary air is required for cooling of the inner casing the gas pressure increases in an axial downstream direction the axial velocity of the gas stream is greatest behind the swirl vanes the gas temperature is highest at the chamber outlet

exemple 282 secondary air is required for cooling of the inner casing. — The combustion system's purpose is to provide a smooth stream of uniformly heated gas with the least loss of pressure and the maximum release of heat . 1047.the combustion chamber is made from two tubes one is the flame tube which is inside the air casing between the two is an air gap through which any air that does not go into the combustion chamber passes secondary air .air enters the combustion chamber at around 500 ft/sec and is diffused to around 80 ft/sec even at this speed the slow flame at 1/2 ft/sec would be blown away so a region of low pressure is created round it to keep it alright secondary air is required for cooling of the inner casing.

If there is a single input data failure on a fadec gas turbine engine ?

Question 34-39 : The engine continues to operate normally the engine stops the engine is set at a fail safe thrust the electronic engine control unit uses a constant data value for computation

exemple 286 the engine continues to operate normally. — the engine continues to operate normally.

Concerning the fuel system high pressure shut off valve hpsov of a gas turbine ?

Question 34-40 : Ignition is activated before fuel is delivered by the hpsov to the fuel nozzles the hpsov is located between the hp fuel pump and the fuel control unit manual hpsov control from the cockpit is not possible with fadec equipped engines the hpsov is mounted in the wing front spar near the pylon

exemple 290 ignition is activated before fuel is delivered by the hpsov to the fuel nozzles. — ignition is activated before fuel is delivered by the hpsov to the fuel nozzles.

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