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Regarding a jet engine .i the maximum thrust increases as the pressure ? [ Report OACI ]

Question 33-1 : I is correct ii is incorrect i is incorrect ii is correct i is correct ii is correct 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 133 I is correct, ii is incorrect.I is correct, ii is incorrect.

One of the advantages of an annular combustion chamber is ?

Question 33-2 : A reduced thermal stress on the turbine that fewer igniters are required a higher structural strength a simpler assembly

A combustion chamber is a very complex structure with its divergent convergent passages compare to old multi can combustion system annular combustion chamber are shorter lighter cheaper with improved combustion characteristics more power and greater efficiency the main driver in combustion chamber development is the need to equalise temperature and flow around the whole turbine entry ring in order to reduced thermal stress exemple 137 A reduced thermal stress on the turbine.A reduced thermal stress on the turbine.

The correct order of decreasing freezing points of the three mentioned fuels is ?

Question 33-3 : Jet a jet a 1 jet b jet b jet a 1 jet a jet a 1 jet a jet b jet b jet a jet a 1

The accepted minimum fuel temperature for safe flight for .jet a is 40°c.jet a 1 is 47°c.jet b is 65°c exemple 141 Jet a, jet a-1, jet b.Jet a, jet a-1, jet b.

Labyrinth seals in the lubrication system of a gas turbine engine are designed ?

Question 33-4 : Not completely tight allowing some movement between rotating and static parts not completely tight allowing only some radial movement between rotating and static parts completely tight allowing no movement between rotating and static parts completely tight allowing some axial movement between rotating and static parts

exemple 145 Not completely tight, allowing some movement between rotating and static parts.Not completely tight, allowing some movement between rotating and static parts.

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

Question 33-5 : 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 149 I is correct, ii is correct.I is correct, ii is correct.

The characteristics of an axial compressor are .1 a low pressure ratio by ?

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

Img914.the key word here is by stage a centrifugal compressor will produce about 5 1 ratio per stage ie impeller & diffuser compared to a axial that gives about 1 2 1 per stage however the use of multi stage axial compressors gives a bigger overall ratio exemple 153 1, 3.1, 3.

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

Question 33-7 : I is correct ii is correct i is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is incorrect

There is a velocity decrease as air flows from a small inlet to a larger outlet exemple 157 I is correct, ii is correct.I is correct, ii is correct.

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

Question 33-8 : I is correct ii is correct i is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is incorrect

In a divergent duct with subsonic flow the static pressure rises as does static temperature but the total temperature remains constant exemple 161 I is correct, ii is correct.I is correct, ii is correct.

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

Question 33-9 : I is correct ii is correct i is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is incorrect

exemple 165 I is correct, ii is correct.I is correct, ii is correct.

A flat rated turbofan engine has a constant maximum rated thrust level ?

Question 33-10 : Up to a specific oat up to a specific pressure altitude above a specific oat above a specific 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 169 Up to a specific oat.Up to a specific oat.

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

Question 33-11 : I is correct ii is incorrect i is incorrect ii is correct i is correct ii is correct i is incorrect ii is incorrect

exemple 173 I is correct, ii is incorrect.I is correct, ii is incorrect.

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

Question 33-12 : I is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect i is correct ii is correct

The speed flow is reduced static pressure increases dynamic pressure decreases and total pressure remains unchanged there is no total temperature changes but static temperature increases while dynamic temperature decreases exemple 177 I is incorrect, ii is incorrect.I is incorrect, ii is incorrect.

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

Question 33-13 : I is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect i is correct ii is correct

Static pressure increases dynamic pressure decreases and total pressure remains unchanged there is no total temperature changes

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

Question 33-14 : I is incorrect ii is incorrect i is correct ii is correct i is correct ii is incorrect i is incorrect ii is correct

Static pressure increases dynamic pressure decreases and total pressure remains unchanged there is no total temperature changes but static temperature increases while dynamic temperature decreases exemple 185 I is incorrect, ii is incorrect.I is incorrect, ii is incorrect.

Which statement is correct about the flow in a divergent jet engine inlet .i ?

Question 33-15 : I is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect i is correct ii is correct

The flow speed decreases static pressure increases dynamic pressure decreases and total pressure remains unchanged

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

Question 33-16 : I is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is correct

Static pressure increases dynamic pressure decreases and total pressure remains unchanged there is no total temperature changes but static temperature increases while dynamic temperature decreases exemple 193 I is incorrect, ii is incorrect.I is incorrect, ii is incorrect.

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

Question 33-17 : I is incorrect ii is incorrect i is incorrect ii is correct i is correct ii is incorrect i is correct ii is correct

Static pressure increases dynamic pressure decreases and total pressure remains unchanged there is no total temperature changes but static temperature increases while dynamic temperature decreases exemple 197 I is incorrect, ii is incorrect.I is incorrect, ii is incorrect.

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

Question 33-18 : I is correct ii is correct i is incorrect ii is incorrect i is incorrect 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 exemple 201 I is correct, ii is correct.I is correct, ii is correct.

A twin spool engine with an inlet air mass flow of 220 kg/s and a hp compressor ?

Question 33-19 : 0 1 1 1 10

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.220 220 = 0.0/220 = 0.bypass ratio = 0 exemple 205 0.0.

A turbofan engine with an inlet air mass flow of 200 kg/s and a hp compressor ?

Question 33-20 : 9 10 5 11

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.200 20 = 180.180/20 = 9 exemple 209 9.9.

A turbofan engine with an inlet air mass flow of 220 kg/s and a hp compressor ?

Question 33-21 : 10 11 1 1 12

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.220 20 = 200.200 / 20 = 10 exemple 213 10.10.

A turbofan engine with a bypass air mass flow of 200 kg/s and a hp compressor ?

Question 33-22 : 10 11 1 1 9

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.200/20 = 10 exemple 217 10.10.

A turbofan engine with an inlet air mass flow of 220 kg/s and a bypass mass ?

Question 33-23 : 10 11 1 1 9

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.220 200 = 20.200 / 20 = 10 exemple 221 10.10.

The throttle lever angle tla information of a fadec controlled gas turbine ?

Question 33-24 : To the electronic engine control unit by a direct electrical wiring connection to the hydro mechanical main engine control via cables and pulleys to a single dedicated channel of the fadec

Tla thrust lever angle indicates the position of the thrust lever in control stand from a reference point usually this is 0° when thrust lever is at idle and increases up to 40° when thrust lever is advanced to take off position .this thrust lever is connected by mechanical linkages to an electrical resolver synchro sensor called thrust lever angle resolver the resolver has a stator and rotor the angle of the rotor with respect to stator reference point changes as thrust lever is moved this angle is called thrust lever resolver angle tra .this resolver is connected to electronic engine control eec to control engine thrust for different positions of the thrust lever exemple 225 To the electronic engine control unit by a direct electrical wiring connection.To the electronic engine control unit by a direct electrical wiring connection.

A twin spool engine with a bypass mass flow of 250 kg/s and a hp compressor ?

Question 33-25 : 1 2 0 0 5

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.250 / 250 = 1 exemple 229 1.1.

Which of the following statements regarding variable inlet guide vanes vigvs ?

Question 33-26 : Vigvs are located at the front of the hp compressor and together with the vsvs control compressor airflow vigvs are located in the front of the fan and control both fan and compressor air flow vsvs are used in the compressor only and are used to increase pressure ratio vigvs prevent lp compressor stall and vsvs prevent hp compressor stall if vigvs move towards the open position vsvs move towards the closed position

The compression system is usually split into two units a low pressure lp compressor mounted on one shaft followed by an high pressure hp compressor mounted on the hp shaft and driven by its own hp turbine . 952.the fan blades of the general electric engine on a boeing 747 800 behind the fan the compressor inlet guide vanes inner circle and variable stator vanes outer circle can be seen exemple 233 Vigvs are located at the front of the hp compressor and, together with the vsvs, control compressor airflow.Vigvs are located at the front of the hp compressor and, together with the vsvs, control compressor airflow.

A turbofan engine with an inlet air mass flow of 300 kg/s and a hp compressor ?

Question 33-27 : 5 6 1 7

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.300 50 = 250.250 / 50 = 5 exemple 237 5.5.

A turbofan engine with a bypass mass flow of 250 kg/s and a hp compressor mass ?

Question 33-28 : 5 6 1 4

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.hp compressor mass flow = 50 .bypass = 250.250 / 50 = 5

A turbofan engine with an inlet air mass flow of 300 kg/s and a bypass mass ?

Question 33-29 : 5 6 1 2

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.inlet = 300.bypass = 50.hp compressor mass flow 300 50 = 250.bypass ratio = 250 / 50 = 5 exemple 245 5.5.

A turbofan engine with a bypass mass flow of 888 kg/s and a hp compressor mass ?

Question 33-30 : 8 9 1 12 7

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.888 / 111 = 8

Bleeding air from the hp compressor of a turbofan whilst maintaining thrust ?

Question 33-31 : Egt and fuel flow hp compressor discharge pressure and n2 n2 and fuel flow egt and n1

Oscarjp .if there is less air flow coming in egt will rise in function of that and because there is a loss on efficiency due to the bleed more work is demanded to the system and so fuel flow increases exemple 253 Egt and fuel flow.Egt and fuel flow.

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

Question 33-32 : 1 2 0 3

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.inlet = 500.bypass = 250 > compressor = 250.250 / 250 = 1 exemple 257 1.1.

Compressor stall is due to ?

Question 33-33 : An excessively high angle of attack of the rotor blades an excessively low angle of attack of the rotor blades an excessively high axial velocity an inadequate fuel flow

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 261 An excessively high angle of attack of the rotor blades.An excessively high angle of attack of the rotor blades.

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

Question 33-34 : 8 01 9 01 1 12 10 01

Img939.bypass ratio = bypass mass flow / hp compressor mass flow.bypass mass flow = 1000 111 = 889.889 / 111 = 8 01 exemple 265 8.01.8.01.

Which of these statements about an reaction turbine are correct or incorrect .i ?

Question 33-35 : I is correct ii is incorrect i is correct ii is correct i is incorrect ii is correct i is incorrect ii is incorrect

There is a pressure drop and a velocity increase across the stator of a reaction turbine exemple 269 I is correct, ii is incorrect.I is correct, ii is incorrect.

The electronic engine control of a fadec gas turbine engine checks ?

Question 33-36 : All input and output data active channel input and output data only input data only output data only

The full authority digital engine control system fadec receives all the necessary data for engine operation and takes over virtually all of the steady state and transient control functions which includes compressor airflow control vigv's vsv's etc exemple 273 All input and output data.All input and output data.

Jet engine total efficiency indicates the efficiency at which ?

Question 33-37 : Chemical power in the fuel is transformed into propulsive power t x v chemical power in the fuel is transformed into an increase of jet kinetic energy per second the increase of jet kinetic energy is transformed into propulsive energy potential energy in the jet is transformed into propulsive energy

exemple 277 Chemical power in the fuel is transformed into propulsive power (t x v).Chemical power in the fuel is transformed into propulsive power (t x v).

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

Question 33-38 : 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 decrease for a gas turbine engine with a constant speed propeller and free power turbine when the power setting is decreased exemple 281 I is correct, ii is correct.I is correct, ii is correct.

The fadec of a gas turbine engine consists of ?

Question 33-39 : An electronic engine control unit and its peripherals fuel metering actuators electrical wiring sensors an electronic engine control unit only all electronic engine control units installed on the aircraft an electronic engine control unit and the engine display units in the cockpit

exemple 285 An electronic engine control unit and its peripherals (fuel metering, actuators, electrical wiring, sensors).An electronic engine control unit and its peripherals (fuel metering, actuators, electrical wiring, sensors).

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

Question 33-40 : I is incorrect ii is correct i is correct ii is incorrect i is incorrect ii is incorrect 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 exemple 289 I is incorrect, ii is correct.I is incorrect, ii is correct.

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