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One reason to fit a tip shroud to a turbine blade is to ? [ Mandatory security ]

Question 42-1 : 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 142 Increase turbine efficiency.Increase turbine efficiency.

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

Question 42-2 : Oil pressure oil temperature oil quantity oil filter clogged warning signal

exemple 146 Oil pressure.Oil pressure.

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

Question 42-3 : 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 150 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 42-4 : 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 154 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 42-5 : 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 158 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 42-6 : 2 3 1 2 3 1 4 2 3 4

exemple 162 2, 3.2, 3.

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

Question 42-7 : 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 166 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 42-8 : 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 170 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 42-9 : 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 174 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 42-10 : Shut down the engine select the other igniter system move the thrust lever forward to increase fuel flow activate both igniter systems

exemple 178 Shut down the engine.Shut down the engine.

Compressor surge may be controlled by means of ?

Question 42-11 : 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 42-12 : 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 186 3 only.3 only.

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

Question 42-13 : 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 42-14 : The lp turbine the hp turbine the hp compressor through reduction gearing airflow drawn across it by the hp compressor

exemple 194 The lp turbine.The lp turbine.

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

Question 42-15 : 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 198 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 42-16 : 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 202 Malfunction of the heat exchanger.Malfunction of the heat exchanger.

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

Question 42-17 : 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 206 3500 n.3500 n.

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

Question 42-18 : 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 210 Of 8.01Of 8.01

Exhaust gas temperature sensing is usually taken ?

Question 42-19 : 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 214 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 42-20 : 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 218 Ambient temperature.Ambient temperature.

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

Question 42-21 : Turbine section compressor section casing of the combustion chamber jet pipe

exemple 222 Turbine section.Turbine section.

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

Question 42-22 : 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 226 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 42-23 : 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 230 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 42-24 : 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 234 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 42-25 : 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 238 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 42-26 : 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

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

Question 42-27 : 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 246 I is correct, ii is correct.I is correct, ii is correct.

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

Question 42-28 : I is incorrect ii is incorrect i is correct ii is incorrect i is incorrect ii is correct i is correct ii is correct

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 and not by volume exemple 250 I is incorrect, ii is incorrect.I is incorrect, ii is incorrect.

Compressor stall in a gas turbine engine ?

Question 42-29 : Can be caused by an axial airflow velocity that is low relative to the rotor speed does not occur with well designed compressor blades is unlikely to occur in a compressor with many stages only occurs during engine start up

.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 exemple 254 Can be caused by an axial airflow velocity that is low relative to the rotor speed.Can be caused by an axial airflow velocity that is low relative to the rotor speed.

The air flow passages between adjacent axial compressor rotor blades are ?

Question 42-30 : Part of the compressor work delivered to the air is converted into kinetic energy it is a constant temperature process the compressor rotational velocity slows down the air flow the gas expands between the blades

.compression of hot gas in the rotor is followed by an expansion before entering the stator exemple 258 Part of the compressor work delivered to the air is converted into kinetic energy.Part of the compressor work delivered to the air is converted into kinetic energy.

A twin spool gas turbine engine is one in which the ?

Question 42-31 : Lp turbine drives the lp compressor and the hp turbine drives the hp compressor lp compressor drives the hp compressor turbines are free to rotate at speeds that differ from their associated compressors lp turbine drives both the lp compressor and the hp compressor

exemple 262 Lp turbine drives the lp compressor and the hp turbine drives the hp compressor.Lp turbine drives the lp compressor and the hp turbine drives the hp compressor.

When the combustion gases pass through a turbine the ?

Question 42-32 : Pressure drops pressure rises axial velocity of the flow decreases temperature increases

exemple 266 Pressure drops.Pressure drops.

The most common extinguishing agent used in gas turbine engine fire protection ?

Question 42-33 : A liquid halogenated extinguishing agent and pressurized gas typically nitrogen water co2 powder

exemple 270 A liquid halogenated extinguishing agent and pressurized gas (typically nitrogen).A liquid halogenated extinguishing agent and pressurized gas (typically nitrogen).

When a part of a continuous loop fire detection system is heated .1 its ?

Question 42-34 : 1 and 3 2 and 3 1 and 4 2 and 4

exemple 274 1 and 3.1 and 3.

A fault protection circuit in a fire detection system will ?

Question 42-35 : Inhibit the fire detector when the detection line is connected to ground activate an alarm in the cockpit and in the landing gear bay for ground crew activate the fire detection system when the detection line is connected to ground automatically initiate apu shutdown and fire extinguisher striker activation in the event of fire

A fault protection circuit in a fire detection system will inhibit fire detection when the detection line is connected to ground so if a fire detection system with no fault protection has single loop continuous components if the line is accidentally grounded the alarm will be triggered exemple 278 Inhibit the fire detector when the detection line is connected to ground.Inhibit the fire detector when the detection line is connected to ground.

In a fire detection system with single loop continuous components with no fault ?

Question 42-36 : The fire alarm is triggered the engine fire extinguisher striker is automatically activated there will be no effect on the system the power supply is cut off automatically

exemple 282 The fire alarm is triggered.The fire alarm is triggered.

When a continuous loop wire type fire detection system is tested ?

Question 42-37 : The wiring and the warning are tested the wire is totally heated only the warning function is tested a part of the wire is totally heated

exemple 286 The wiring and the warning are tested.The wiring and the warning are tested.

Regarding fire detection ion detectors are used to detect ?

Question 42-38 : Smoke overtemperature and fire fire overtemperature

exemple 290 Smoke.Smoke.

Smoke detector systems are installed in the ?

Question 42-39 : Upper cargo compartments class e wheel wells engine nacelles fuel tanks

exemple 294 Upper cargo compartments (class e).Upper cargo compartments (class e).

Continuous loop fire detector systems operate on the principle that an increase ?

Question 42-40 : A decrease in resistance an increase in resistance a decrease in the reference current a decrease in pressure

exemple 298 A decrease in resistanceA decrease in resistance

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