15.11 Fuel Systems

Question 1

What are the requirements for fuel systems?

Answer 1

-increase decrease power
-adapt for changes for ambient pressure or temperature
-respond to rapid acceleration demands

Question 2

What is the hydro mechanical/ electronic fuel control?

Answer 2

A hybrid of the two types of control but can be set to purely hydro mechanical.
Input/ output is electronically controlled fuel flow is set by servo motors

Question 3

How does FADEC function?

Answer 3

-uses electronic inputs
-fuel flow is electronically outputted

Question 4

What are the two sections of hydromechanical fuel control?

Answer 4

Computing
Monitoring

Question 5

Which fuel control systems require no electric interface?

Answer 5

Hydro mechanical

Question 6

What is one disadvantage of hydromechanical fuel control?

Answer 6

It is not as accurate

Question 7

in a hydromechanical electronic fuel system what type of system does a more advanced electronic control system use to adjust fuel flow?

Answer 7

a remotely located electronic engine control

Question 8

what is the function of the engine fuel system?

Answer 8

-pressurise the fuel
-meter fuel flow
-deliver atomised flow

Question 9

in a hydromechanical electronic fuel control system what controls fuel flow to the combustion section?

Answer 9

the hydromechanical fuel control assembly

Question 10

what does the hydromechanical fuel section have?

Answer 10

a fuel shut off section and a fuel metering unit

Question 11

what does the vane type fuel pump give?

Answer 11

a fixed displacement pump which provides high pressure fuel

Question 12

what gives indication of filter bypass valve activation?

Answer 12

a differential pressure indicator

Question 13

on a hydromechanical electric type what is fuel metering provided to?

Answer 13

the EFCU

Question 14

what do the engine generated control signals include?

Answer 14

-fan spool speed
-inner turbine temp
-fan discharge temp
-compressor discharge pressure

Question 15

what is the engine mounted power levers purpose on a hydro mechanical electrical fuel systems?

Answer 15

it receives electrical signal from the throttle lever

Question 16

where are engine generated and aircraft generated control signals sent to?

Answer 16

EFCU

Question 17

where is the EFCU mounted in the hydro mechanical electrical fuel system?

Answer 17

the airframe

Question 18

what is the FADEC?

Answer 18

full authority digital electronic control

Question 19

what does the FADEC use to sense engine parameters?

Answer 19

electronic sensors

Question 20

where is information sent to on the FADEC?

Answer 20

EEC

Question 21

what are the two channels contained by the EEC?

Answer 21

Channel A
Channel B

Question 22

how are EEC channels stored and where?

Answer 22

they are physically separated and cooled by convection

Question 23

what supplies the EEC with a signal in proportion with thrust lever position in the FADEC?

Answer 23

throttle lever angle resolver

Question 24

what does cross talk logic provide in FADEC systems?

Answer 24

Channel A & B

Question 25

where is the fuel metering unit mounted on the FADEC?

Answer 25

on the face of the gearbox and fuel pump

Question 26

what does the EEC provide position feed back engine components using?

Answer 26

-RVDT -LVDT -Thermocouples

Question 27

what does the programming plug do in the FADEC?

Answer 27

it selects proper software in the EEC for the engine thrust rating

Question 28

what is the primary and secondary fuel system?

Answer 28

primary - stores secondary - supplies

Question 29

what is the function of the recirculation valve?

Answer 29

to cool fuel in preparation for it being pumped back into the fuel tank

Question 30

what is the function of the servo heater?

Answer 30

to heat fuel more if necessary

Question 31

what is the function of the return bypass line?

Answer 31

bypass excess fuel

Question 32

what are the two types of engine driven pumps?

Answer 32

constant displacement non constant displacement

Question 33

where would a non constant displacement pump be used?

Answer 33

inlet of the engine driven pump

Question 34

how is the fuel pump lubricated?

Answer 34

by fuel passing through the pump

Question 35

what is the low pressure filter installed to prevent?

Answer 35

to protect the engine driven fuel pump

Question 36

where is the high pressure filter installed?

Answer 36

between fuel pump and fuel control

Question 37

where is the low pressure filter installed?

Answer 37

between supply tanks and the engine fuel systems

Question 38

which filter is the highest filtering capacity?

Answer 38

the micron filter

Question 39

what are the two most common filters?

Answer 39

-200 mesh & 35 mesh micron

Question 40

what does the single fuel manifold do?

Answer 40

supplies fuel to each nozzle

Question 41

what is the use for a shroud?

Answer 41

it carrys leaks to the fuel mast

Question 42

what are the two methods to protect fluid lines against leaks?

Answer 42

shrouded connections doubles seal connections

Question 43

on older aircraft how did fuel leak protection differ?

Answer 43

there were two fuel supply lines and two fuel manifolds -primary supplied the primary fuel line and the secondary supplied the secondary

Question 44

how do duplex and simplex nozzles differ?

Answer 44

duplex usually require dual manifolds

Question 45

why are two sets of simplex nozzles usually required?

Answer 45

one for a smaller discharge at idle speeds and one with a larger orifice for accelerations to max

Question 46

how do dual flow nozzles differ?

Answer 46

they contain two nozzles in one component

Question 47

what is the function of a check valve in a fuel nozzle?

Answer 47

to prevent carbon build up

Question 48

when is fuel likely to be pumped back to the tank?

Answer 48

in low pressure modes