Book 3 - Engine HP Fuel System

Question 1

the power (_____) of a gas turbine engine is controlled by metering the quantity of ____ injected into the combustion system. varying the fuel flow will lead to variations in engine _____, thus altering the mass air flow and thrust

Answer 1

the power (THRUST) of a gas turbine engine is controlled by metering the quantity of FUEL injected into the combustion system. varying the fuel flow will lead to variations in engine SPEED, thus altering the mass air flow and thrust

Question 2

the thrust requirement is initially set by the control _____ in the cockpit

Answer 2

the thrust requirement is initially set by the control LEVER in the cockpit

Question 3

the system must _________ the engine from excessive ___, temperatures and thrusts

Answer 3

the system must SAFEGUARD the engine from excessive RPM, temperatures and thrusts

Question 4

the HP fuel shut off valve (HP ____) is used to ____ the engine and to keep the fuel system ______ when the engine is stationary

Answer 4

the HP fuel shut off valve (HP COCK) is used to STOP the engine and to keep the fuel system PRIMED when the engine is stationary

Question 5

in a turbo-prop aircraft, the throttle _____ and propeller control ____ are usually ____________ to provide ______ lever control

Answer 5

in a turbo-prop aircraft, the throttle LEVER and propeller control UNIT are usually INTERCONNECTED to provide SINGLE lever control

Question 6

when a higher thrust is required, the throttle is _______ and the pressure to the burners _________ due to the greater flow of ____. this increases temperature and ________ through the turbine giving a higher engine speed, greater mass ____ and increased thrust

Answer 6

when a higher thrust is required, the throttle is OPENED and the pressure to the burners INCREASES due to the greater flow of FUEL. this increases temperature and VELOCITY through the turbine giving a higher engine speed, greater mass FLOW and increased thrust

Question 7

changes in altitude, air __________ and forward air _____ all change the density of the air at the intake and the weight of air drawn through the engine. fuel flow must be automatically _______ to maintain the desired RPM and thrust levels

Answer 7

changes in altitude, air TEMPERATURE and forward air SPEED all change the density of the air at the intake and the weight of air drawn through the engine. fuel flow must be automatically CHANGED to maintain the desired RPM and thrust levels

Question 8

HP fuel is supplied to the ________ in sufficient quantity from flow generated from a __________ pump, generally driven from the engine ________

Answer 8

HP fuel is supplied to the BURNERS in sufficient quantity from flow generated from a MECHANICAL pump, generally driven from the engine GEARBOX

Question 9

HP fuel pumps may be simple ____ gear pumps, which deliver output directly related to gearbox _____, or more complex _________ displacement pumps, which can vary their output irrespective of the speed of the engine

Answer 9

HP fuel pumps may be simple SPUR gear pumps, which deliver output directly related to gearbox SPEED, or more complex VARIABLE displacement pumps, which can vary their output irrespective of the speed of the engine

Question 10

the output of the ________ plunger or piston fuel pumps is controlled by a series of plungers which are rotated via a drive from the engine gearbox. the plunger position is set by the angle of a ___ plate, the larger the angler of the plate, the _______ the output of the pump.

the position of the cam plate is controlled by a ______ piston which moves according to a pressure in the fuel system that is sensitive to the variables

Answer 10

the output of the VARIABLE plunger or piston fuel pumps is controlled by a series of plungers which are rotated via a drive from the engine gearbox. the plunger position is set by the angle of a CAM plate, the larger the angler of the plate, the GREATER the output of the pump.

the position of the cam plate is controlled by a SERVO piston which moves according to a pressure in the fuel system that is sensitive to the variables

Question 11

if the cam plate in the variable displacement pump is set in the vertical position, i.e. zero angle, then no ________ in fuel flow will occur

if the system demands more fuel, there is an _________ in servo pressure, which forces the plate across and increases cam plate ______. as the angle increases, the plungers now increase their stroke, therefore creating an _________ fuel flow in the system

Answer 11

if the cam plate in the variable displacement pump is set in the vertical position, i.e. zero angle, then no INCREASE in fuel flow will occur

if the system demands more fuel, there is an INCREASE in servo pressure, which forces the plate across and increases cam plate ANGLE. as the angle increases, the plungers now increase their stroke, therefore creating an INCREASE fuel flow in the system

Question 12

variable displacement pump over speed protection is set using a __________ spring and servo pressure ______ valve

should the engine exceed its maximum safe working limit, the pressure of the fuel under the _________ (created by __________ force) will be enough to overcome the _______ of the governor spring and will open the servo pressure spill valve

this bleeds off servo pressure, reducing ___ plate angle, and therefore reducing fuel flow

as RPM drops, the __________ spring pulls the diaphragm back down and closes the ______ spill valve

Answer 12

variable displacement pump over speed protection is set using a GOVERNOR spring and servo pressure SPILL valve

should the engine exceed its maximum safe working limit, the pressure of the fuel under the DIAPHRAGM (created by CENTRIFUGAL force) will be enough to overcome the TENSION of the governor spring and will open the servo pressure spill valve

this bleeds off servo pressure, reducing CAM plate angle, and therefore reducing fuel flow

as RPM drops, the GOVERNOR spring pulls the diaphragm back down and closes the SERVO spill valve

Question 13

servo pressure within a variable displacement pump is regulated using either a ____ ball valve or ________ knife

Answer 13

servo pressure within a variable displacement pump is regulated using either a HALF ball valve or KINETIC knife

Question 14

an engine overspeed and successful operation of the HP pump governor system would present itself in the flight deck by the engine RPM _______ around its maximum permissible value

this would indicate a fault in the fuel control system and correct operation of the governor system

Answer 14

an engine overspeed and successful operation of the HP pump governor system would present itself in the flight deck by the engine RPM HUNTING around its maximum permissible value

this would indicate a fault in the fuel control system and correct operation of the governor system`

Question 15

servo pressure is generated from a restricted ____ of pump output pressure. so therefore, as pump output increases, servo pressure _________

control of servo pressure is achieved by the use of ______ within the system, which open and close in response to specific conditions, thus regulating pump output to compensate

Answer 15

servo pressure is generated from a restricted SPILL of pump output pressure. so therefore, as pump output increases, servo pressure INCREASES

control of servo pressure is achieved by the use of VALVES within the system, which open and close in response to specific conditions, thus regulating pump output to compensate

Question 16

the half ball type servo valve will pivot open, allowing servo pressure to _____ or pivot closed, allowing servo pressure to increase

Answer 16

the half ball type servo valve will pivot open, allowing servo pressure to BLEED or pivot closed, allowing servo pressure to increase

Question 17

the kinetic knife servo valve consists of two ________ jets, one subjected to pump _________ pressure, the other subjected to pump servo pressure

when the knife is withdrawn, the jet from pump delivery pressure jet causes servo pressure to ________, increasing pump output

when the knife is lowered, the jets are separated from each other, allowing servo pressure to ______ away, decreasing pump output

the blade can be placed in an __________ position to allow a slow spill and maintain a ________, constant output from the pump

Answer 17

the kinetic knife servo valve consists of two OPPOSING jets, one subjected to pump DELIVERY pressure, the other subjected to pump servo pressure

when the knife is withdrawn, the jet from pump delivery pressure jet causes servo pressure to INCREASE, increasing pump output

when the knife is lowered, the jets are separated from each other, allowing servo pressure to BLEED away, decreasing pump output

the blade can be placed in an INTERMEDIATE position to allow a slow spill and maintain a BALANCED, constant output from the pump

Question 18

changes in ambient conditions must be compensated for by changing fuel flow

the simplest way of doing this is using a pressure _________ capsule assembly

the pressure sensitive capsule is connected to a ________ line in the engine _____ and will expand or contract with changes in air pressure

increased ____ flow will be required when inlet pressure increases which could be caused by increased density, pressure, temperature or velocity.

increase intake pressure will cause __________ capsule to expand, causing spill valve to _____. this will increase servo pressure and pump output

reduction will do the opposite

Answer 18

changes in ambient conditions must be compensated for by changing fuel flow

the simplest way of doing this is using a pressure SENSITIVE capsule assembly

the pressure sensitive capsule is connected to a SENSING line in the engine INTAKE and will expand or contract with changes in air pressure

increased FUEL flow will be required when inlet pressure increases which could be caused by increased density, pressure, temperature or velocity.

increase intake pressure will cause EVACUATED capsule to expand, causing spill valve to CLOSE. this will increase servo pressure and pump output

reduction will do the opposite

Question 19

in its simplest form the throttle is mechanically connected to a _______ shaped valve which restricts the fuel flow, the amount of restriction dependent upon the position of the sliding valve

this valve has a ____________ in that there is limited control over acceleration or deceleration of the engine

should the pilot make a large, sudden increase in throttle position, an over ________ situation could occur which would reduce engine __________ and potentially cause a stall or surge

in mechanical systems, this is avoided by the use of a ________ throttle which regulates increase or reduction of fuel with pilot input

Answer 19

in its simplest form the throttle is mechanically connected to a NEEDLE shaped valve which restricts the fuel flow, the amount of restriction dependent upon the position of the sliding valve

this valve has a DISADVANTAGE in that there is limited control over acceleration or deceleration of the engine

should the pilot make a large, sudden increase in throttle position, an over FUELLING situation could occur which would reduce engine EFFICIENCY and potentially cause a stall or surge

in mechanical systems, this is avoided by the use of a DASHPOT throttle which regulates increase or reduction of fuel with pilot input

Question 20

the dashpot throttle is held in position by throttle _____ pressure opposed by throttle control pressure plus ______ force

Answer 20

the dashpot throttle is held in position by throttle SERVO pressure opposed by throttle control pressure plus SPRING force

Question 21

the pressure drop control system adjust pump output to reflect the pressure drop sensed across the throttle control valve.

if the _______ valve is opened too quickly, the the pressure upstream of the valve will ____ rapidly. this drop will be sensed on top of the diaphragm and the spring, assisted by downstream pressure will close the _____ valve, increasing pump servo pressure and output which restores pressure in line to the ________

a quick movement of throttle to the closed position will do the opposite

Answer 21

the pressure drop control system adjust pump output to reflect the pressure drop sensed across the throttle control valve.

if the THROTTLE valve is opened too quickly, the the pressure upstream of the valve will DROP rapidly. this drop will be sensed on top of the diaphragm and the spring, assisted by downstream pressure will close the SERVO valve, increasing pump servo pressure and output which restores pressure in line to the BURNERS

a quick movement of throttle to the closed position will do the opposite