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The compressor blades in a rotating gas turbine engine are held in position by ? [ Quiz landing ]

Question 49-1 : The mountings and the resultant of aerodynamic and centrifugal forces abradable seals and aerodynamic forces a centrifugal latch the mountings and thermal expansion only

exemple 149 The mountings and the resultant of aerodynamic and centrifugal forces.The mountings and the resultant of aerodynamic and centrifugal forces.

Some gas turbine engines have multiple stages in the hp and lp turbines ?

Question 49-2 : Because one stage does not generate sufficient shaft power to facilitate balancing of the turbine assembly to help stabilise the pressure between the compressor and the turbine to reduce noise in the propelling nozzle

exemple 153 Because one stage does not generate sufficient shaft power.Because one stage does not generate sufficient shaft power.

In which part of a gas turbine engine are high temperature requirements most ?

Question 49-3 : The combustion chamber and front part of the hp turbine the last part of the hp compressor and front part of the hp turbine the turbine and exhaust nozzle the combustion chamber and exhaust nozzle

Usually titanium alloy is the material used for the combustion chamber and high pressure turbine exemple 157 The combustion chamber and front part of the hp turbine.The combustion chamber and front part of the hp turbine.

A twin spool engine with an inlet air mass flow of 500 kg/s and a hp compressor ?

Question 49-4 : 1 0 2 3

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.500 250 = 250.250 / 250 = 1 exemple 161 1.1.

A 'fan' stage of a ducted fan turbine engine is driven by ?

Question 49-5 : The low pressure turbine airflow drawn across it by the high pressure compressor the high pressure compressor through reduction gearing the high pressure turbine

Img948 exemple 165 The low pressure turbine.The low pressure turbine.

The oil supply to gas turbine engine bearings is maintained in the event of the ?

Question 49-6 : Differential pressure opening the bypass valve of the main oil filter the hp fuel pump the scavenge pumps a back up oil system

exemple 169 Differential pressure opening the bypass valve of the main oil filter.Differential pressure opening the bypass valve of the main oil filter.

One of the purposes of compressor bleed valves is to ?

Question 49-7 : Decrease the airflow across the rear compressor stages whilst that across the early stages is increased limit the acceleration period of the engine increase the airflow across the rear compressor stages whilst that across the early stages is decreased decrease the load on the compressor when the engine is approaching maximum rpm

Bleed valves are fitted to prevent compressors stalling .vdo1055.like the stall of a wing compressor stall is caused by a breakdown of airflow .the bleed valve removes excesss volume of air at low compressor speeds to increase the flow over the front compressor blades and reduce the flow over the latter stages .as speed of the compressor increases the bleed valve closes exemple 173 Decrease the airflow across the rear compressor stages, whilst that across the early stages is increased.Decrease the airflow across the rear compressor stages, whilst that across the early stages is increased.

Turbine blade stages may be classed as either 'impulse' or 'reaction' in an ?

Question 49-8 : I drops ii remains constant i rises ii remains constant i remains constant ii drops i remains constant ii rises

Img940.nozzle guide vanes = stator .the pressure drops across the stator blades and remains constant across the rotor blades exemple 177 (i) drops (ii) remains constant(i) drops (ii) remains constant

One advantage of having three instead of two spools in some high bypass ?

Question 49-9 : Fewer variable stator vanes and variable inlet guide vanes are required to prevent compressor stall at low rotor speeds fewer variable stator vanes and variable inlet guide vanes are required to prevent compressor stall at high rotor speeds there is a lower fuel consumption due to a higher overall pressure ratio there is a lower fuel consumption and more thrust due to higher overall pressure ratio

Variable inlet guide vanes v i g v s are fitted to engines which have a particular problem with inherent compressor stall at low rpm or during engine acceleration or deceleration the vanes are fitted just in front of the first rotor stage they can be automatically pivoted around their own axis to vary the path of the airflow going into the compressor so maintaining the proper relationship between compressor rotational speed and airflow in the front compressor stages at low compressor speeds the v i g v s are angled to impart the greatest amount of swirl to the air thereby correcting the relative airflow to obtain the optimum angle of attack over the rotor blades this optimum angle of attack allows a smooth and rapid engine acceleration .on a three spools high bypass turbofan engine an additional intermediate pressure compressor stage is added and reduces the risk of compressor stall at low rotor speeds

The compressor surge effect during acceleration is prevented by the ?

Question 49-10 : Fuel control unit f c u variable setting type nozzle guide vanes surge bleed valves inlet guide vanes

With modern engines there are various ways to control surge one of them is the use of blow off valves also called compressor bleed valves .on all modern turbine engines with electronic fuel control systems the valves are controlled by the fuel control unit .the end result will be that the blow off valve will reduce the pressure in the compressor to prevent the surge exemple 185 Fuel control unit (f.c.u.).Fuel control unit (f.c.u.).

Creep in a gas turbine engine is ?

Question 49-11 : The permanent increase in length of metal parts due to a combination of tensile stress and high temperatures over a prolonged period expansion of metal parts due to temperature increase the elastic increase in length of metal parts due to tensile stress and high temperatures crack formation in metal parts due to cyclic mechanical loads and high temperatures

About a twin spool compressor ?

Question 49-12 : The low pressure spool runs at a lower rpm than the high pressure spool both spools run at the same rpm the low pressure spool runs at a very high rpm thus preventing the onset of compressor stall when operating at very high rpm's the later stages within the high pressure spool will have a large negative angle of attack

exemple 193 The low pressure spool runs at a lower rpm than the high pressure spool.The low pressure spool runs at a lower rpm than the high pressure spool.

In addition to providing 'customer' bleed for aeroplane systems air may be bled ?

Question 49-13 : At low rotor speed at high rotor speed and prevent stall at high rotor speed and recover from stall at high rotor speed

During engine starts most turbojet/turbofan engines use engine bleed air to reduce the possibility of compressor stalls .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 also happens with centrifugal type compressor .bleeding air from an engine air is bled just aft of the compressor relieves that excessive pressure and the compressor can more easily 'push' the sucked air behind him exemple 197 At low rotor speed.At low rotor speed.

One reason to fit a tip shroud to a turbine blade is to ?

Question 49-14 : Increase turbine efficiency provide a seal for the cooling airflow prevent blade creep reduce turbine temperatures

The shrouded blades form a band around the perimeter of the turbine which serves to reduce blade vibrations the shrouds improve the airflow characteristics and increase the efficiency of the turbine the shrouds also serve to cut down gas leakage around the tips of the turbine blades exemple 201 Increase turbine efficiency.Increase turbine efficiency.

The most important oil system instrument indication during gas turbine engine ?

Question 49-15 : Oil pressure oil temperature oil quantity oil filter clogged warning signal

exemple 205 Oil pressure.Oil pressure.

Turbine blade stages may be classed as either 'impulse' or 'reaction' in an ?

Question 49-16 : The pressure drops across the stator blades and remains constant across the rotor blades the pressure rises across the stator blades and remains constant across the rotor blades the pressure remains constant across the stator blades and drops across the rotor blades the pressure remains constant across stator blades and rises across the rotor blades

Img940.nozzle guide vanes = stator .the pressure drops across the stator blades and remains constant across the rotor blades exemple 209 The pressure drops across the stator blades and remains constant across the rotor blades.The pressure drops across the stator blades and remains constant across the rotor blades.

When a gas turbine engine is fitted with can type combustion chambers ?

Question 49-17 : A total of only two igniters are usually fitted since the chambers are inter connected each chamber has its own igniter each chamber is fitted with one igniter and one glow plug each chamber is fitted with two igniters

Most gas turbine engines only have two igniters typically located diagonally opposed in fact the engine would probably start quite readily with only one operating however because there are only two another means of passing the starting flame between the combustion chambers has to be found this is the interconnector exemple 213 A total of only two igniters are usually fitted since the chambers are inter-connected.A total of only two igniters are usually fitted since the chambers are inter-connected.

The purpose of gas turbine engine trending is ?

Question 49-18 : To enhance maintenance planning and detect anomalies to collect metal particles from the oil system to assess engine condition using non destructive inspection to obtain a timely indication when an engine requires to be shut down due to problems

Engine trending performance analysis monitoring and diagnostics permit to enhance maintenance planning and to detect anomalies exemple 217 To enhance maintenance planning and detect anomalies.To enhance maintenance planning and detect anomalies.

The flexible take off mode .1 can be used only if the engines are recent.2 ?

Question 49-19 : 2 3 1 2 3 1 4 2 3 4

exemple 221 2, 3.2, 3.

Concerning the flexible take off mode the temperature selected in the fms is ?

Question 49-20 : Higher than the ambiant airfield temperature in order to achieve a reduced power setting lower than the ambiant airfield temperature in order to achieve a reduced power setting higher than the ambiant airfield temperature in order to achieve an increased power setting lower than the ambiant airfield temperature in order to achieve an increased power setting

. extract from boeing fcom flight crew operations manual .assumed temperature reduced thrust .regulations permit the use of up to 25% takeoff thrust reduction for operation with assumed temperature reduced thrust use of assumed temperature reduced thrust is not allowed with anti skid inoperative or on runways contaminated with standing water ice slush or snow use of assumed temperature reduced thrust is not recommended if potential windshear conditions exist .a takeoff thrust less than the full rated thrust may be achieved by using an.assumed temperature that is higher than the actual temperature exemple 225 Higher than the ambiant airfield temperature, in order to achieve a reduced power setting.Higher than the ambiant airfield temperature, in order to achieve a reduced power setting.

One reason to fit a tip shroud to a turbine blade is to ?

Question 49-21 : Reduce blade vibrations and limit marginal leaks provide a seal for the cooling airflow reduce turbine temperatures prevent blade creep

The shrouded blades form a band around the perimeter of the turbine which serves to reduce blade vibrations the shrouds improve the airflow characteristics and increase the efficiency of the turbine the shrouds also serve to cut down gas leakage around the tips of the turbine blades exemple 229 Reduce blade vibrations and limit marginal leaks.Reduce blade vibrations and limit marginal leaks.

On a high by pass ratio fan engine reverse thrust is achieved by reversing ?

Question 49-22 : Only the direction of the fan airflow only the direction of the exhaust gas flow the direction of rotation of the fan the direction of both the exhaust gas flow hot stream and the fan airflow cold stream

On high bypass turbofan engines reverse thrust is achieved by reversing only the direction of the fan airflow 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 exemple 233 Only the direction of the fan airflow.Only the direction of the fan airflow.

If an abortive start hung start occurs when starting a gas turbine engine the ?

Question 49-23 : Shut down the engine select the other igniter system move the thrust lever forward to increase fuel flow activate both igniter systems

exemple 237 Shut down the engine.Shut down the engine.

Compressor surge may be controlled by means of ?

Question 49-24 : Bleed valves a pressure drop control orifice fixed inlet guide vanes a variable metering orifice

The use of igniters in a gas turbine engine is required .1 throughout the ?

Question 49-25 : 3 only 1 and 2 1 and 3 2 only

Normally in flight no igniters are in use as the combustion is self sustaining during engine start and for take off and landing igniters are in use .you have to use igniters in case of moderate or severe precipitation turbulence or icing or for an in flight relight exemple 245 3 only.3 only.

Vibration sensors are used in a gas turbine engine to indicate ?

Question 49-26 : Imbalance of one or both of the spools that there is too much free movement of the engine strut pylon that tip clearance of turbine blades has decreased below a minimum value bearing problems only

The fan of a turbo fan engine is driven by ?

Question 49-27 : The lp turbine the hp turbine the hp compressor through reduction gearing airflow drawn across it by the hp compressor

exemple 253 The lp turbine.The lp turbine.

Regarding a jet engine .i the maximum thrust increases as the pressure altitude ?

Question 49-28 : I is correct ii is correct i is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is incorrect

.jet engines are more efficient at higher altitudes because less fuel is needed for a given thrust due to reduction in lift and drag and lower temperatures through the inlet cause a significant reduction in specific fuel consumption up to the tropopause .specific fuel consumption is the amount of fuel burnt per unit of thrust for jets it reduces with altitude up to the tropopause exemple 257 I is correct, ii is correct.I is correct, ii is correct.

One of the causes of high oil temperature in a gas turbine engine at constant ?

Question 49-29 : Malfunction of the heat exchanger unusually high scavenge pump oil flow high oil pressure high outside air temperature

.the fuel/oil heat exchanger is located in the tanks it cools the oil and heats the fuel so if at constant power setting you have a high oil temperature it may come from a malfunction of the heat exchanger exemple 261 Malfunction of the heat exchanger.Malfunction of the heat exchanger.

Given the following information about an aeroplane with a turbojet engine . ?

Question 49-30 : 3500 n 4000 n 3000 n 2500 n

Jaredleto .the formula required to answer this question is .total thrust = mass thrust + pressure thrust.or t = m vj vv + a pj p0 .where m = mass air flow vj = exhaust velocity vv = tas .a = exhaust cross section area pj = exhaust static pressure and.p0 = static ambient pressure .in this instance the pressures are given in hpa and need to be converted to n/sq m .therefore t = 50 150 90 + 0 1 105000 100000 which gives the answer of 3500 n exemple 265 3500 n.3500 n.

A turbofan engine with an inlet air mass flow of 1000 kg/s and a bypass mass ?

Question 49-31 : Of 8 01 of 1 12 of 2 12 of 17 02

Img939.1000 889 = 111.889 / 111 = 8 01..bypass ratio = bypass mass flow / hp compressor mass flow exemple 269 Of 8.01Of 8.01

Exhaust gas temperature sensing is usually taken ?

Question 49-32 : Between the gas generator turbine and the free power turbine at the outlet from the combustion chamber after the free power turbine between the stages of the gas generator turbine

exemple 273 Between the gas generator turbine and the free power turbine.Between the gas generator turbine and the free power turbine.

Flat rated jet engines are designed to provide constant maximum take off thrust ?

Question 49-33 : Ambient temperature ambient pressure engine pressure ratio pressure altitude

.the term flat rating is so called because of the flat nature of thrust versus the ambient temperature curve the curve shows that from the lowest operating temperature possible to the specified temperature the engine produces full thrust above this temperature full thrust will not be permitted .a 'flat rated' turbofan engine is controlled in such a way that at constant ambient air pressure there is no variation of take off thrust with air temperature up to some specified temperature limit .above that limit the engine operates in such a way that either . the fan speed or the compressor speed is constant or . the turbine inlet temperature is constant.and in either case the thrust then decreases with increasing temperature exemple 277 Ambient temperature.Ambient temperature.

Engine temperature limitations of a gas turbine engine are usually imposed due ?

Question 49-34 : Turbine section compressor section casing of the combustion chamber jet pipe

exemple 281 Turbine section.Turbine section.

For a fan jet engine the by pass ratio is the ?

Question 49-35 : External airflow mass divided by the internal airflow mass internal airflow mass divided by the external airflow mass internal airflow mass divided by the fuel flow mass fuel flow mass divided by the internal airflow mass

Img939.bypass ratio = bypass mass flow / hp compressor mass flow .by pass mass flow is the external airflow .hp compressor mass flow is the internal airflow mass exemple 285 External airflow mass divided by the internal airflow mass.External airflow mass divided by the internal airflow mass.

If the main oil filter of a gas turbine engine becomes clogged oil to the main ?

Question 49-36 : Because the oil filter bypass valve opens because fuel upstream of the oil filter will be mixed with oil to allow easier passage through the filter if a higher engine rpm is selected to increase oil pressure if breather pressure in the main compartments is increased to ensure positive lubrication of the bearings

exemple 289 Because the oil filter bypass valve opens.Because the oil filter bypass valve opens.

In a free turbine engine the energy delivered by the free turbine stages ?

Question 49-37 : Is dependent on the rotational speed of the gas generator is used to drive the compressor and the main rotor gearbox is not connected with the rotation speed of the generator is used to drive the compressor only

Julien35 .from bristol book 'free power turbine engine the mechanical link between the gas generator and the propeller turbine is removed so each element is free to rotate at its optimum speed' .. but read the question carefully it talk about the energy delivered by the free turbine stages .if the gas generator does not rotate the free turbine stages will delivered 0 energy if the free turbine stages deliver full thrust it is possible only with a high rotational speed of the gas generator .so the energy delivered by the free turbine stages is dependent on the rotational speed of the gas generator exemple 293 Is dependent on the rotational speed of the gas generator.Is dependent on the rotational speed of the gas generator.

Which statement is correct for a gas turbine engine with a constant speed ?

Question 49-38 : I is correct ii is correct i is correct ii is incorrect i is incorrect ii is incorrect i is incorrect ii is correct

Hp spool speed egt and gas generator speed all increase for a gas turbine engine with a constant speed propeller and free power turbine when the power setting is increased exemple 297 I is correct, ii is correct.I is correct, ii is correct.

Which statement is correct for a gas turbine engine with a constant speed ?

Question 49-39 : I is correct ii is correct i is correct ii is incorrect i is incorrect ii is incorrect i is incorrect ii is correct

Hp spool speed egt and gas generator speed all increase for a gas turbine engine with a constant speed propeller and free power turbine when the power setting is increased exemple 301 I is correct, ii is correct.I is correct, ii is correct.

The bypass ratio .i is the ratio of bypass air mass flow to hp compressor mass ?

Question 49-40 : I is correct ii is correct i is correct ii is incorrect i is incorrect ii is correct i is incorrect ii is incorrect

Img939.bypass ratio = bypass mass flow / hp compressor mass flow .the bypass ratio can be determined from the inlet air mass flow and the bypass mass flow exemple 305 I is correct, ii is correct.I is correct, ii is correct.

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1919 Free Training Exam Other source study: Furious atpl examen 49