15.11 Fuel Systems Flashcards
What are the requirements for fuel systems?
-increase decrease power
-adapt for changes for ambient pressure or temperature
-respond to rapid acceleration demands
What is the hydro mechanical/ electronic fuel control?
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
How does FADEC function?
-uses electronic inputs
-fuel flow is electronically outputted
What are the two sections of hydromechanical fuel control?
Computing
Monitoring
Which fuel control systems require no electric interface?
Hydro mechanical
What is one disadvantage of hydromechanical fuel control?
It is not as accurate
in a hydromechanical electronic fuel system what type of system does a more advanced electronic control system use to adjust fuel flow?
a remotely located electronic engine control
what is the function of the engine fuel system?
-pressurise the fuel
-meter fuel flow
-deliver atomised flow
in a hydromechanical electronic fuel control system what controls fuel flow to the combustion section?
the hydromechanical fuel control assembly
what does the hydromechanical fuel section have?
a fuel shut off section and a fuel metering unit
what does the vane type fuel pump give?
a fixed displacement pump which provides high pressure fuel
what gives indication of filter bypass valve activation?
a differential pressure indicator
on a hydromechanical electric type what is fuel metering provided to?
the EFCU
what do the engine generated control signals include?
-fan spool speed
-inner turbine temp
-fan discharge temp
-compressor discharge pressure
what is the engine mounted power levers purpose on a hydro mechanical electrical fuel systems?
it receives electrical signal from the throttle lever
where are engine generated and aircraft generated control signals sent to?
EFCU
where is the EFCU mounted in the hydro mechanical electrical fuel system?
the airframe
what is the FADEC?
full authority digital electronic control
what does the FADEC use to sense engine parameters?
electronic sensors
where is information sent to on the FADEC?
EEC
what are the two channels contained by the EEC?
Channel A
Channel B
how are EEC channels stored and where?
they are physically separated and cooled by convection
what supplies the EEC with a signal in proportion with thrust lever position in the FADEC?
throttle lever angle resolver
what does cross talk logic provide in FADEC systems?
Channel A & B
where is the fuel metering unit mounted on the FADEC?
on the face of the gearbox and fuel pump
what does the EEC provide position feed back engine components using?
-RVDT
-LVDT
-Thermocouples
what does the programming plug do in the FADEC?
it selects proper software in the EEC for the engine thrust rating
what is the primary and secondary fuel system?
primary - stores
secondary - supplies
what is the function of the recirculation valve?
to cool fuel in preparation for it being pumped back into the fuel tank
what is the function of the servo heater?
to heat fuel more if necessary
what is the function of the return bypass line?
bypass excess fuel
what are the two types of engine driven pumps?
constant displacement
non constant displacement
where would a non constant displacement pump be used?
inlet of the engine driven pump
how is the fuel pump lubricated?
by fuel passing through the pump
what is the low pressure filter installed to prevent?
to protect the engine driven fuel pump
where is the high pressure filter installed?
between fuel pump and fuel control
where is the low pressure filter installed?
between supply tanks and the engine fuel systems
which filter is the highest filtering capacity?
the micron filter
what are the two most common filters?
-200 mesh & 35 mesh micron
what does the single fuel manifold do?
supplies fuel to each nozzle
what is the use for a shroud?
it carrys leaks to the fuel mast
what are the two methods to protect fluid lines against leaks?
shrouded connections
doubles seal connections
on older aircraft how did fuel leak protection differ?
there were two fuel supply lines and two fuel manifolds
-primary supplied the primary fuel line and the secondary supplied the secondary
how do duplex and simplex nozzles differ?
duplex usually require dual manifolds
why are two sets of simplex nozzles usually required?
one for a smaller discharge at idle speeds and one with a larger orifice for accelerations to max
how do dual flow nozzles differ?
they contain two nozzles in one component
what is the function of a check valve in a fuel nozzle?
to prevent carbon build up
when is fuel likely to be pumped back to the tank?
in low pressure modes
