Jet engine total efficiency indicates the efficiency at which ?
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Which statement is correct for a gas turbine engine with a constant speed propeller and free power turbine when the power setting is decreased I The HP spool speed decreases II The EGT decreases ?
The FADEC of a gas turbine engine consists of ?
The bypass ratio i the ratio of inlet air mass flow to exhaust air mass flow ii can be determined from bypass air mass flow and hp compressor mass flow I incorrect ii correct. bypass ratio = bypass mass flow / hp compressor mass flow the bypass ratio can be determined from inlet air mass flow the bypass mass flow. 
The fadec of a gas turbine engine normally includes An engine overspeed and/or an egt protection function. bypass ratio = bypass mass flow / hp compressor mass flow the bypass ratio can be determined from inlet air mass flow the bypass mass flow. 
In a gas turbine engine propelling jet generated Expansion of hot gases resulting in a conversion of potential energy (pressure) into kinetic energy (velocity). The process of energy conversion in a multistage turbine consists of a number of successive processes in individual stages compressed heated gas at an initial velocity passes through blade to blade channels of nozzle assembly where in course of expansion part of available heat drop converted into kinetic energy of exhaust flow further gas expansion conversion of heat drop into useful work take place in blade to blade channels of rotor the gas flow acting on rotor blades develops torque on turbine's shaft as a result absolute velocity of gas reduced the lower this velocity larger part of available gas energy that converted into mechanical work on shaft the rotor blades receive forces produced a change in direction of gas velocity flowing around them (impulse flow effect) by acceleration of gas flow relative to movement in blade to blade channels (reaction flow effect). 
The internal geometry of a turbofan intake a subsonic commercial aeroplane Divergent in order to reduce airflow velocity increase static pressure in front of fan. in a divergent intake flow speed decreases the static pressure increases dynamic pressure decreases total pressure remains unchanged. Question 33-8
The turbine in a gas turbine engine generates shaft power using Expansion of hot gas followed conversion of kinetic energy (velocity) into (mechanical) work. The expansion the drop of pressure like a venturi tube velocity must increase to keep same mass flow this kinetic energy of hot gases converted into useful rotational mechanical energy the turbine this increased velocity (kinetic energy) what drives shaft. Question 33-9
The principle of aeroplane propulsion to generate a propelling force Accelerating air or gas in order to obtain a reaction force. The expansion the drop of pressure like a venturi tube velocity must increase to keep same mass flow this kinetic energy of hot gases converted into useful rotational mechanical energy the turbine this increased velocity (kinetic energy) what drives shaft. Question 33-10
Which statement correct a gas turbine engine with a constant speed propeller and free power turbine when power setting increased i the gas generator speed decreases ii the egt remains constant I incorrect ii incorrect. Hp spool speed egt gas generator speed all increase a gas turbine engine with a constant speed propeller free power turbine when power setting increased. Question 33-11
Which statement correct a gas turbine engine with a constant speed propeller and free power turbine when power setting increased i the gas generator speed decreases ii the egt decreases I incorrect ii incorrect. Hp spool speed egt gas generator speed all increase a gas turbine engine with a constant speed propeller free power turbine when power setting increased. Question 33-12
The primary performance indicator cockpit instrument the thrust of a turbofan engine I incorrect ii incorrect. Primary engine indications n1 epr egt are primary engine indications on a turbofan engine secondary engine indications n2 fuel flow oil pressure oil temperature oil quantity engine vibration are secondary engine indications a turbofan engine a dual rotor axial flow turbofan the n1 rotor consists of a fan a low pressure compressor a low?pressure turbine the n2 rotor consists of a high pressure compressor a high pressure turbine the n1 n2 rotors are mechanically independent epr engine pressure ratio it compares pressure in engine inlet with pressure in exhaust nozzle n1 the speed of first stage engine compressor this used as a power setting in most jet engines. Question 33-13
If air tapped from a gas turbine hp compressor effect on engine pressure ratio epr and exhaust gas temperature egt that Epr decreases egt increases. If you bleed air from compressor you are reducing pressure inside compressor therefore turbine outlet pressure will be reduced if inlet pressure remains same outlet pressure reduced then epr decreases since hot air tapped directly from a compressor stage temperature will rise in turbine egt increases. Question 33-14
An abortive hung start the term used to describe an attempt to start in which engine Lights up but fails to accelerate sufficiently. After normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall hung starts may be caused 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 variable stators turbine section damage. Question 33-15
On a fadec jet engine meaning of f a d e c on a gas turbine engine Full authority digital engine control. After normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall hung starts may be caused 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 variable stators turbine section damage. Question 33-16
The blades in an axial flow compressor decrease in size from Low pressure to high pressure stages in an attempt to sustain axial velocity. the blades size reduces from inlet until output of compressor. Question 33-17
Regarding a jet engine i the maximum thrust decreases slightly as pressure altitude decreases ii the specific fuel consumption increases slightly as pressure altitude decreases at constant tas I incorrect ii correct. Jet engines are more efficient at higher altitudes because less fuel needed a given thrust due to reduction in lift drag lower temperatures through inlet cause a significant reduction in specific fuel consumption up to tropopause specific fuel consumption the amount of fuel burnt per unit of thrust for jets it reduces with altitude up to tropopause notice as pressure altitude decreases means 'at a lower altitude'. Question 33-18
Which of following statements correct about flow in a divergent subsonic gas turbine engine intake i the speed decreases in flow direction ii the total pressure decreases in flow direction I correct ii incorrect. In a divergent intake flow speed decreases the static pressure increases dynamic pressure decreases total pressure remains unchanged. Question 33-19
Which of following statements correct about flow in a divergent subsonic gas turbine engine intake i the static pressure increases in flow direction ii the total temperature increases in flow direction I correct ii incorrect. In a divergent intake flow speed decreases the static pressure increases dynamic pressure decreases total pressure remains unchanged. Question 33-20
Both gas turbine and piston engines use a cycle made up of induction compression combustion and exhaust phases which of these statements about a gas turbine are correct or incorrect i the process in a gas turbine engine intermittent ii theoretically combustion occurs at constant volume I incorrect ii incorrect. piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder turbine engine combustion process continuous occurs at constant pressure. Question 33-21
Which of following statements correct about flow in a divergent subsonic gas turbine engine intake i the speed remains constant in flow direction ii the total pressure remains constant in flow direction I incorrect ii correct. There a velocity decrease as air flows from a small inlet to a larger outlet. Question 33-22
Which statement correct about flow in a divergent jet engine inlet i the static pressure remains constant in flow direction ii the total temperature remains constant in flow direction I incorrect ii correct. There a velocity decrease as air flows from a small inlet to a larger outlet. Question 33-23
Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at low rpm ii a compressor stall most likely to occur when air flow stagnates in rear stages of compressor I correct ii correct. Like stall of a wing compressor stall caused a breakdown of airflow if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow) you can prevent this dumping some late stage air to atmosphere (via bleed valves). Question 33-24
In a compressor stage if axial air velocity increases more than rotor blade velocity Stall margin increases. compressor stall occurs when compressor sucks too much air the turbine wheels to handle excessive pressure then builds aft of compressor the compressor blades stall a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow when incoming air flow speed high blade angle of attack will be low stall margin increases (there less risk to encounter a compressor stall). Question 33-25
Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at high rpm ii a compressor stall most likely to occur when air flow stagnates in rear stages of compressor I incorrect ii correct. Like stall of a wing compressor stall caused a breakdown of airflow if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow) you can prevent this dumping some late stage air to atmosphere (via bleed valves). Question 33-26
With regard to a twin spool turbofan an abortive start hung start will result in N2 speed stabilising at a lower than normal rpm a subsequent increase in egt. after normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall hung starts may be caused 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 variable stators turbine section damage. Question 33-27
Which of following statements correct about flow in a divergent subsonic gas turbine engine intake i the dynamic pressure increases in flow direction ii the static temperature increases in flow direction I incorrect ii correct. after normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall hung starts may be caused 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 variable stators turbine section damage. Question 33-28
One of functions of a gas turbine engine subsonic intake to Decrease airflow velocity. after normal light up sequence (until starter 'cut out') a hung start identified light off followed abnormally slow acceleration rpm stabilization below idle a hung start may be result of fuel scheduling being either too lean or too rich a lean hung start associated with low fuel flow proportionally low egt a rich condition can be recognized a high fuel flow an egt rise which may tend to develop into an over temperature condition possible compressor stall hung starts may be caused 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 variable stators turbine section damage. Question 33-29
One of advantages of multiple spool jet engine designs that A smaller air starter driving only a single spool can be used. the air starter motor possibly most popular starting system presently in use it light simple to use very economical utilizing low pressure air the air starter motor fastened to accessory gearbox of engine the sources of air available 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 used air from one of these sources fed through an electrically controlled start valve to air inlet to rotate turbine rotor 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 other spools. Question 33-30
Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at high rpm ii a compressor stall most likely to occur when air flow stagnates in front stages of compressor I incorrect ii incorrect. Like stall of a wing compressor stall caused a breakdown of airflow if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow) you can prevent this dumping some late stage air to atmosphere (via bleed valves). Question 33-31
After a successful start of a high bypass turbofan engine air starter Is disengaged the coupling between engine n2 spool starter the use of centrifugal forces. Air starting used on most commercial some military jet engines it has many advantages over other starting systems is comparatively light simple economical to operate 10 an air starter motor transmits power through a reduction gear clutch to starter output shaft which connected to engine the starter turbine rotated 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 starter controlled an elec trically operated control pressure reducing valve that opened when an engine start selected is automatically closed at a predetermined starter speed the clutch also automatically disengages as engine accelerates up to idling rpm the rotation of starter ceases. Question 33-32
Both gas turbine and piston engines use a cycle made up of induction compression combustion and exhaust phases which of these statements about a gas turbine are correct or incorrect i the process in a gas turbine engine continuous ii theoretically combustion occurs at constant volume I correct ii incorrect. piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder turbine engine combustion process continuous occurs at constant pressure. Question 33-33
Which of these statements about compressor stall are correct or incorrect i a compressor stall most likely to occur in a compressor designed a high pressure ratio operating at low rpm ii a compressor stall most likely to occur when air flow stagnates in front stages of compressor I correct ii incorrect. Like stall of a wing compressor stall caused a breakdown of airflow if your wing suitable high speed you fly at low speed large angle of attack stall most likely to occur a compressor stall most likely to occur when air flow stagnates in rear stages of compressor a compressor blade hitting oncoming airflow at an angle of attack that determined a combination of rotational speed the incoming airflow when incoming speed low angle of attack will be high when angle of attack gets too high blade stalls so when axial flow in a compressor backs up blades stall (pressure increase in rear stages this slows down flow) you can prevent this dumping some late stage air to atmosphere (via bleed valves). Question 33-34
The following problems may occur when starting a twin spool turbofan engine No n rotation although n2 may accelerate normally. during engine start compressor very inefficient if engine experiences more than usual difficulty accelerating (due to such problems as early starter cut out fuel mis scheduling or strong tailwinds) engine may spend a considerable time at very low rpm (sub idle) normal engine cooling flows will not be effective during sub idle operation turbine temperatures may appear relatively high this known as a hot start. Question 33-35
Both gas turbine and piston engines use a cycle made up of induction compression combustion and exhaust phases which of these statements about a gas turbine are correct or incorrect i the process in a gas turbine engine intermittent ii theoretically combustion occurs at constant pressure I incorrect ii correct. piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder turbine engine combustion process continuous occurs at constant pressure. Question 33-36
The most unfavourable conditions adequate inlet air flow of a turbofan engine are Maximum take off thrust zero forward speed strong crosswind conditions. piston engine combustion process intermittent governed the rythm of back forth movements of piston in a cylinder the combustion occurs at constant volume in cylinder turbine engine combustion process continuous occurs at constant pressure. Question 33-37
If a twin spool gas turbine engine controlled a conventional n2 control system rupture of lp shaft may result in Overspeed of lp turbine. In a twin spool engine lp turbine connected to lp compressor hp turbine connected to hp compressor the lp turbine drives lp compressor if a rupture occurs it may result in an overspeed of lp turbine. Question 33-38
The rotor blades of an axial compressor of a gas turbine engine are often mounted on a disk or drum using a 'loose fit' because this Limits damage to blades due to vibration. In a twin spool engine lp turbine connected to lp compressor hp turbine connected to hp compressor the lp turbine drives lp compressor if a rupture occurs it may result in an overspeed of lp turbine. Question 33-39
For a turbine engine self sustaining speed relates to minimum rpm at which engine Will continue to operate without any starter motor assistance. In a twin spool engine lp turbine connected to lp compressor hp turbine connected to hp compressor the lp turbine drives lp compressor if a rupture occurs it may result in an overspeed of lp turbine. Question 33-40
The primary function of diffuser located between compressor and combustion chamber of a gas turbine engine to Decrease flow velocity. Before combustion can proceed air velocity must be greatly reduced air leaves compressor through exit guide vanes which convert radial component of air flow out of compressor to straight line flow the air then enters diffuser section of engine which a very divergent duct the primary function of diffuser structure aerodynamic the divergent duct shape converts most of air's velocity (pi) into static pressure (ps) as a result highest static pressure lowest velocity in entire engine at point of diffuser discharge combustor inlet other aerodynamic design considerations that are important in diffuser section arise from need a short flow path uniform flow distribution low drag loss.
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