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At constant fuel flow if engine compressor air is bled off for engine anti ? [ Questionnaire LAPL ]

Question 32-1 : Will rise will be unchanged will fall may rise or fall depending on which stage of the compressor is used for the bleed and the rpm of the engine at the moment of selection

The ratio of the tertiary airflow around the combustion flame tube that cools the turbine decreases thus less cooling flow as the warm air is diverted for anti icing so the egt will increase as a result exemple 132 Will rise.Will rise.

A hung abortive start of a gas turbine engine may be caused by ?

Question 32-2 : A too low pneumatic starter pressure compressor surging the starter cutting out early in the starting sequence before the engine has accelerated to the required rpm for ignition failure of the fuel to ignite in the starting sequence after the engine has been accelerated to the required rpm by the starter

.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 exemple 136 A too low pneumatic starter pressure.A too low pneumatic starter pressure.

A reverse thrust alert on the flight deck occurs when .1 the reverser doors ?

Question 32-3 : 1 3 2 4 1 4 2 3

Boeing fcom .thrust reverser .each engine is equipped with a hydraulically operated thrust reverser consisting of left and right translating sleeves aft movement of the reverser sleeves causes blocker doors to deflect fan discharge air forward through fixed cascade vanes producing reverse thrust the thrust reverser is for ground operations only and is used after touchdown to slow the airplane reducing stopping distance and brake wear .when reverse thrust is selected an electro mechanical lock releases the isolation valve opens and the thrust reverser control valve moves to the deploy position allowing hydraulic pressure to unlock and deploy the reverser system an interlock mechanism restricts movement of the reverse thrust lever until the reverser sleeves have approached the deployed position when either reverser sleeve moves from the stowed position the amber rev indication located on the upper display unit illuminates as the thrust reverser reaches the deployed position the rev indication illuminates green and the reverse thrust lever can be raised to detent no 2 this position provides adequate reverse thrust for normal operations when necessary the reverse thrust lever can be pulled beyond detent no 2 providing maximum reverse thrust .downward motion of the reverse thrust lever past detent no 1 reverse idle thrust initiates the command to stow the reverser when the lever reaches the full down position the control valve moves to the stow position allowing hydraulic pressure to stow and lock the reverser sleeves after the thrust reverser is stowed the isolation valve closes and the electro mechanical lock engages .if the reverser doors are unlocked with the reverse lever in the stowed position or if the reverser doors remain stowed with the reverse lever in the deployed position the reverser light illuminates the master caution and eng system annunciator lights illuminate exemple 140 1, 3.1, 3.

In a single spool gas turbine engine the compressor rpm is ?

Question 32-4 : The same as turbine rpm independent of turbine rpm greater than turbine rpm less than turbine rpm

The turbine is turning the compressor so one turbine and one compressor . 912. single spool gas turbine engine exemple 144 The same as turbine rpm.The same as turbine rpm.

The primary reason for a limitation being imposed on the temperature of the gas ?

Question 32-5 : Ensure that the maximum acceptable temperature at the turbine blades is not exceeded ensure that the maximum acceptable temperature within the combustion chamber is not exceeded prevent damage to the combustion chamber from overheating prevent damage to the jet pipe from overheating

The temperatures are highest in the combustion chamber but the engine is most sensitive to high temperatures just behind the combustion chamber at the turbine high temperatures and centrifugal loads can cause turbine blade creep . 913. jt9d engine exemple 148 Ensure that the maximum acceptable temperature at the turbine blades is not exceeded.Ensure that the maximum acceptable temperature at the turbine blades is not exceeded.

One of the purposes of the bleed valves fitted to axial flow compressors is to ?

Question 32-6 : Reduce the tendency to compressor stall enable an external air supply to spin up the compressor for engine starting spill compressor air should the engine overspeed thus controlling the speed control the acceleration time of the engine

exemple 152 Reduce the tendency to compressor stall.Reduce the tendency to compressor stall.

A modern auxiliary power unit apu is designed to provide power for ground ?

Question 32-7 : Air conditioning and electrical services either air conditioning or electrical services but never both at the same time air conditioning and electrical services on the ground electrical and hydraulic back up services in the air air conditioning and thrust in the event of engine failure

exemple 156 Air conditioning and electrical services.Air conditioning and electrical services.

The disadvantages of axial flow compressors compared to centrifugal flow ?

Question 32-8 : 1 and 3 1 and 2 2 and 4 2 and 3

Img914.compared to centrifugal flow compressors axial flow compressors are more expensive to manufacture .due to the design and function of a compressor engine's air inlet the possibility of ingestion of debris always exists this causes significant damage particularly to the compressor and turbine sections when this occurs it is called foreign object damage fod typical fod consists of small nicks and dents caused by ingestion of small objects from the ramp taxiway or runway .however fod damage caused by bird strikes or ice ingestion can also occur and may result in total destruction of an engine .example of a centrifugal compressor . 915 exemple 160 1 and 3.1 and 3.

A stage in an axial compressor ?

Question 32-9 : Consists of a rotor disc followed by a ring of stator blades has a compression ratio in the order of 2 1 consists of a ring of stator blades followed by a rotor disc has a compression ration in the order of 0 8

exemple 164 Consists of a rotor disc followed by a ring of stator blades.Consists of a rotor disc followed by a ring of stator blades.

In a turbo jet the purpose of the turbine is to ?

Question 32-10 : Drive the compressor by using part of the energy from the exhaust gases clear the burnt gases the expansion of which provide the thrust compress the air in order to provide a better charge of the combustion chamber drive devices like pumps regulator generator

exemple 168 Drive the compressor by using part of the energy from the exhaust gases.Drive the compressor by using part of the energy from the exhaust gases.

The gas turbine illustrated is of the following type . 916 ?

Question 32-11 : Free turbine and centrifugal compressor free turbine and axial compressor single shaft turbine and centrifugal compressor single shaft turbine and axial compressor

For a free power turbine engine the turbine driving the main rotor transmission is mechanically independent from the gas generator . 915. radial centrifugal compressor located at the front of the engine exemple 172 Free turbine and centrifugal compressor.Free turbine and centrifugal compressor.

The control of free turbine engines on turboprops is accomplished by . a ?

Question 32-12 : 1 5 and 6 1 3 and 5 3 4 and 6 2 4 and 5

Propeller control lever controls rpm so out of 1 2 and 3 only 1 is correct .fuel control lever controls torque and turbine temp so out of 4 5 and 6 both 5 and 6 are correct .the correct answer option is then 1 5 6 exemple 176 1, 5 and 6.1, 5 and 6.

The static thrust of a turbo jet at the selection of full power .1 equals the ?

Question 32-13 : 1 and 3 4 only 1 and 2 2 and 3

Static thrust is the measured thrust produced when movement is prevented .thrust in its simplest form is .f = m x a.thrust f = mass flow rate x jet velocity tas .statement 1 it is true .2 it is a nonsense .statement 3 it is true no movement = zero mechanical power .statement 4 wrong static thrust is dependant of the outside air temperature since mass flow will vary with temperature/density

The purpose of a compressor bleed valve is to prevent surging ?

Question 32-14 : At low compressor rpm generated by foreign object ingestion of the first compressor stages with altitude

.the compressor bleed valve removes excesss volume of air at low compressor rpm to increase the flow over the front compressor blades and reduce the flow over the latter stages exemple 184 At low compressor rpm.At low compressor rpm.

Severe compressor stall can be indicated amongst others by ?

Question 32-15 : A rise in turbine gas temperature tgt and a change in vibration level an increase in engine pressure ratio epr and a decrease in tgt and fuel flow a decrease in tgt and a change in vibration level a rise in tgt and an increase in fuel flow

A compressor stall means less cooling flow for the turbine so the egt will increase as a result as for a wing vibrations will occur during the stall

In a gas turbine engine compressor blades which are not rigidly fixed in ?

Question 32-16 : The resultant of aerodynamic and centrifugal forces thermal expansion blade creep oil pressure

The blades are not rigidly fixed one common mehtod of fitting them is with the 'fir tree root' rotor blades are strong enought to withstand centrifugal forces they take up a rigid position when the engine is running due to the resultant of aerodynamic and centrifugal forces .watch the videos below . >beghfv2y2ry. you can here at 6 00 the 'clung' noise of the blade falling from their casing . >phluddufakg. this is for the turbine stage but construction is similar for the compressor stage exemple 192 The resultant of aerodynamic and centrifugal forces.The resultant of aerodynamic and centrifugal forces.

The characteristics of a centrifugal compressor are .1 a high pressure ratio ?

Question 32-17 : 1 and 2 1 and 4 2 and 3 3 and 4

Img938. axial compressor . 915. radial compressor .the pressure ratio obtained from a centrifugal compressor by stage is lower than that which can be obtained from the axial flow compressor by stage .the diameter of a centrifugal compressor is usually larger compare to an axial compressor for the same flow exemple 196 1 and 2.1 and 2.

The diffuser in a centrifugal compressor is a device in which the ?

Question 32-18 : Pressure rises and velocity falls pressure rises at a constant velocity velocity pressure and temperature rise velocity rises and pressure falls

Diffuser = stator for a compressor .in the case of a compressor the velocity falls and the pressure increases in the stator the diffuser exemple 200 Pressure rises and velocity falls.Pressure rises and velocity falls.

The thrust reversers of jet engines may use clamshell doors in order to ?

Question 32-19 : Change the direction of the exhaust gas stream stop the flow of the exhaust gas stream reduce the pressure of the exhaust gas stream by diffusing it to atmosphere absorb any surge in engine thrust

exemple 204 Change the direction of the exhaust gas stream.Change the direction of the exhaust gas stream.

By pass turbine engines are mainly used in commercial aviation because ?

Question 32-20 : At high subsonic airspeeds they have a better propulsive efficiency than propeller or straight jet engines they produce less noise they are lighter than straight jet engines twin spool or triple spool jet engines require a high by pass ratio

exemple 208 At high subsonic airspeeds they have a better propulsive efficiency than propeller or straight jet engines.At high subsonic airspeeds they have a better propulsive efficiency than propeller or straight jet engines.

Engine auxiliary gearboxes ?

Question 32-21 : Provide the drives for a wide variety of services and may even provide for the support of the engine in the airframe always provide drives for fuel pumps oil pumps speed sensing and torque sensing never provide a torque sensing facility are driven by the output from the free power turbine

Img908. 909.the accessory gearbox is driven by a radial shaft that meshes with a bevel gear driven by the n2 or gas producer rotor and is used to drive essential engine components such as the fuel pump oil pump fuel control unit generators and hydraulic pumps .the accessory gear box is also used to drive engine rpm feedback tacho generators and is the means by which the starter drives the engine these are systems which must operate as soon as the engine starts .structure containing the gearbox can be utilised as a support as well .each component that attaches to the accesssory gearbox has its own mounting pad with its unique gear reduction for speed and rotational direction exemple 212 Provide the drives for a wide variety of services and may even provide for the support of the engine in the airframe.Provide the drives for a wide variety of services and may even provide for the support of the engine in the airframe.

The greatest risk created by a free turbine overspeed is ?

Question 32-22 : Bursting of the free turbine disk a surge of the gas generator creep of the turbine blades an engine overtemperature

In case of turbine overspeed centrifugal force can be so great that the turbines rotor blades can detatch .. 942.during a high powered engine run this 767 had a engine failure . 943.piece of the turbine is seen above lodged in the outboard side of the engine . 944.the photo above shows the gash made on the lower part of the fuselage in the air conditioning bay when a piece of the turbine exited the engine and ended up embedding in the engine exemple 216 Bursting of the free turbine disk.Bursting of the free turbine disk.

The thermal efficiency of a gas turbine engine will increase with a ?

Question 32-23 : Decrease in ambient air temperature increase in ambient air temperature increase in humidity decrease in ambient air pressure

Thermal efficiency is the ratio of useful work to the heat put in expressed as a percentage .the power output of a gas turbine engine depends on mass airflow and a cold air mass has higher density thermal efficiency increases with cold ambient air temperature exemple 220 Decrease in ambient air temperature.Decrease in ambient air temperature.

Creep of turbine blades is caused by ?

Question 32-24 : High blade temperature whilst under centrifugal loading prolonged idling at low rpm bending stresses set up by gas pressure static imbalance of the blades

Blade creep is the increase in length of turbine rotor blades during their operating life due to heat and stress exemple 224 High blade temperature whilst under centrifugal loading.High blade temperature whilst under centrifugal loading.

By pass ratio in a turbine engine is the ratio of the ?

Question 32-25 : Cold air mass flow to the hot air mass flow speed of the combusted air to the speed of the by pass air intake air pressure to the turbine delivery air pressure tertiary air mass flow to the primary air mass flow

Img939.bypass ratio = bypass mass flow / hp compressor mass flow .by pass mass flow is cold air mass flow .hp compressor mass flow is the hot air mass flow exemple 228 Cold air mass flow to the hot air mass flow.Cold air mass flow to the hot air mass flow.

On landing and prior to shut down a gas turbine engine should be run at 'ground ?

Question 32-26 : The core temperature to diminish the turbine blade temperature to reduce only the engine to be compressor washed cool oil flushing of bearings particularly those in the turbines

exemple 232 The core temperature to diminish.The core temperature to diminish.

Both gas turbine and piston engines utilise a cycle of induction compression ?

Question 32-27 : I continuous ii constant pressure i continuous ii constant volume i intermittent ii constant pressure i intermittent ii constant volume

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 exemple 236 (i) continuous (ii) constant pressure(i) continuous (ii) constant pressure

For a subsonic airflow in a divergent duct the ?

Question 32-28 : Pressure increases velocity decreases and temperature increases pressure decreases velocity increases and temperature increases pressure increases velocity decreases and temperature decreases pressure decreases velocity increases and temperature decreases

exemple 240 Pressure increases, velocity decreases and temperature increases.Pressure increases, velocity decreases and temperature increases.

An engine pressure ratio epr can be defined as the ratio of ?

Question 32-29 : Jet pipe total pressure to compressor inlet total pressure jet pipe total pressure to combustion chamber pressure combustion chamber pressure to compressor inlet total pressure compressor outlet pressure to compressor inlet total pressure

Epr is defined as the ratio of the total turbine outlet pressure to the total compressor inlet pressure . 947.'total turbine outlet pressure' is 'jet pipe total pressure' exemple 244 Jet pipe total pressure to compressor inlet total pressure.Jet pipe total pressure to compressor inlet total pressure.

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

Question 32-30 : Cold air mass flow divided by the hot air mass flow hot air mass flow divided by the cold air mass flow hot air mass flow divided by the fuel flow fuel flow divided by hot air mass flow

Img939.bypass ratio = bypass mass flow / hp compressor mass flow .by pass mass flow is cold air mass flow .hp compressor mass flow is the hot air mass flow exemple 248 Cold air mass flow divided by the hot air mass flow.Cold air mass flow divided by the hot air mass flow.

The by pass air in a by pass type gas turbine engine promotes lower specific ?

Question 32-31 : Decrease in exhaust gas flow average velocity and higher propulsive efficiency decrease in combustion chamber temperature and higher thermal efficiency increase in exhaust gas flow average velocity thus increasing engine pressure ratio increase in the mean jet temperature and increase in thermal efficiency

Bypass engines have a number of advantages . the bypass air does not need to be combusted to achieve its acceleration since no fuel is needed to heat the air the design is inherently more thermally efficient . the bypass air is given a smaller acceleration so its propulsive efficiency is greater at lower speeds .the reason that answer decrease in combustion chamber temperature and higher thermal efficiency is not correct is that although the engine is more thermally efficient combustion chamber temperatures are not reduced exemple 252 Decrease in exhaust gas flow average velocity and higher propulsive efficiency.Decrease in exhaust gas flow average velocity and higher propulsive efficiency.

In the airflow through a single spool axial flow turbo jet engine the axial ?

Question 32-32 : On exit from the propelling nozzle as it leaves the compressor within the combustion chamber as it leaves the turbine

Single spool axial flow turbo jet engine . 912.the term 'single spool' refers to the fact that there is only one shaft this shaft connects one turbine section to one compressor section .all jet engines in current use are axial flow engines meaning that the compression phase is done axially parallel to the axis of the engine as the air flows through the compressor .axial flow engines are different from early jet engines which compressed air in a centrifugal compressor .the axial velocity of the air is greatest on exit from the propelling nozzle exhaust of the propulsive gases exemple 256 On exit from the propelling nozzle.On exit from the propelling nozzle.

In a jet engine the propelling nozzle ?

Question 32-33 : Must be designed to obtain the correct balance of pressure and velocity to prevent flow separation reduces noise directs the hot gas stream onto the turbine at the optimum angle of attack decreases the velocity and increases the pressure in the jet pipe to provide greater thrust

exemple 260 Must be designed to obtain the correct balance of pressure and velocity to prevent flow separation.Must be designed to obtain the correct balance of pressure and velocity to prevent flow separation.

In a multi spool turbofan engine the fan is driven by ?

Question 32-34 : The rearmost turbine the intermediate turbine the foremost turbine all three turbines since they are on a common shaft with the compressor

The high pressure turbine drives the high pressure compressor .the low pressure turbine drives the fan and the low pressure compressor . 948.therefore we can say that the fan is driven from the rearmost turbine by a shaft exemple 264 The rearmost turbine.The rearmost turbine.

After air has passed through the compressor of a gas turbine engine the ?

Question 32-35 : Temperature will be higher than the inlet temperature velocity will be higher than the inlet velocity pressure will be the same as the inlet pressure velocity will be the same as the inlet velocity

Compression of air generates heat the air is warmer after compression .1 compressed air high pressure flows toward low pressure.2 the compressor sections are in the front of the engine and the turbine in the rear.3 the compressors are attached to the turbines via shafts.4 between the compressor and turbine sections is the combustion chamber where fuel is mixed with the compressed air and iginited .the compressor section is made up of alternating rows rotating blades and stationary vanes that are shaped like wings curved on one side and flat on the other and they function like wings too airflow creates low pressure on the curved side high pressure on the flat this imparts the direction of the airflow toward the rear of the engine high pressure flows toward low pressure .the leading edges of these rotating blades face the leading edge of the stationary blades and as the air cascades through each pair of rotor and stationary vanes it becomes more and more compressed .the air enters the combustion chamber and is rapidly heated and wants to expand but there is only so much room for expansion which is another form of compression so it continues to the rear of the engine where the pressure is lower and it meets the turbines the turbine are like pinwheels the fast flowing compressed air strikes the turbines and causes it them to spin .add more fuel for more heat the compressed air expands faster and the turbines spin faster because they are attached to the compressor section via shaft the compressor spins faster too which compresses incoming air faster and even more .air does not like to be compressed it likes to be in its normal state so it roars past the turbines out the back of the engine and the reaction thrust of the exhaust against the engine itself causes the propulsion exemple 268 Temperature will be higher than the inlet temperature.Temperature will be higher than the inlet temperature.

To achieve reverse thrust on a turbine engine with a high by pass ratio ?

Question 32-36 : The fan flow is deflected the fan is stopped the direction of rotation of the fan is reversed the flow of hot stream air is reversed

exemple 272 The fan flow is deflected.The fan flow is deflected.

An aircraft flying in conditions of continuous heavy rain and high ambient ?

Question 32-37 : Engine igniters airframe de icing only engine intake anti icing only both engine intake anti icing and airframe de icing

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 276 Engine igniters.Engine igniters.

The engine type represented in the drawing is a . 951 ?

Question 32-38 : Twin spool turbofan single spool turbofan twin spool turbojet triple spool turbofan

exemple 280 Twin-spool turbofan.Twin-spool turbofan.

When the combustion gases pass through a turbine the ?

Question 32-39 : Pressure drops pressure rises axial velocity decreases temperature increases

exemple 284 Pressure drops.Pressure drops.

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

Question 32-40 : 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 288 I is correct, ii is correct.I is correct, ii is correct.

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