Fuel Systems and Control Flashcards
The entire system which stores,
carries, and controls the fuel supply
for the engines can be divided into
two sections. These are:
- airframe fuel system
- engine fuel system
receives the
low pressure fuel supply from the
aircraft fuel tanks which are part of
the airframe fuel system.
engine fuel system
increases the
fuel pressure to a value that the fuel
nozzles in the combustion chamber
can use with the use of fuel pump,
and then controls the volume of fuel
into the engine with the use of fuel
control unit into the engine so that it
conforms to the engine’s
requirement.
engine fuel system
situated in the wing, pass fuel
through non-return valves to the
engine via the low pressure fuel cock.
booster pumps
can be
used to shut off the supply of fuel to
the engine to facilitate the removal of
fuel system components.
low pressure fuel cock
Using the low pressure fuel cock to
shut down the engine, instead of the
high pressure fuel cock, will mean
that the engine will take much
shorter/longer to shutdown.
longer
sometimes called the backing pump,
backs up the fuel supply to the
engine in the event of failure of the
booster pumps in the wing tanks.
low pressure fuel pump
the low pressure fuel pump is sometimes called the
backing pump
maintain a positive pressure at the
inlet of the high pressure pump.
low pressure fuel pumps
serves the
double purpose of cooling the oil and
also heating the fuel.
fuel cooled air cooler
these may block component downstream in the fuel system
formation of ice crystals
incorporates a
valve to maintain the oil pressure in
the cooler higher than the fuel
pressure. This ensures that, in the
case of an internal leak, oil leaks into
the fuel system rather than fuel
leaking into the oil system.
oil cooler feed line
working in
conjunction with the fuel cooled air
cooler, uses compressor bleed air to
warm the fuel to automatically
maintain a predetermined fuel
temperature.
fuel heater
used to open or close a valve which
regulates the entry of hot air into the
fuel heater from the engine
compressor.
automatic temperature control
protects the HP fuel
pump and the fuel control unit from
the effects of dirt or contamination.
LP fuel filter
The filter of an LP fuel filter is a replaceable paper filter
element which is capable of filtering
out particles larger than
50 to 100 microns
measures the
instantaneous fuel flow in gallons per
hour, kilograms per hour, or pounds
per hour, and may also include an
________ which can add
the total amount of fuel used.
flowmeter; integrating system
fitted to and
driven by the engine accessory
gearbox. The engine accessory
gearbox itself is driven by the
HP fuel pump; HP compressor shaft
are rotated
against a stationary camplate which
causes them to reciprocate within
the bores that contain them on the
rotor assembly.
plungers
The distance that the plungers move
during this reciprocating action is
dictated by the
angle of inclination of camplate
controlled by a servo
piston which itself is controlled from
the fuel control unit.
angle of inclination of the camplate
the angle of inclination of the camplate is controlled by a _______ which itself is controlled from
the fuel control unit.
servo piston
composed of a
number of wire mesh screen disks, is
incorporated in the output of the
high pressure fuel pump.
filter
is
simpler and lighter in construction
than the plunger type, and is also
driven by the accessory gearbox.
spur gear type fuel pump
The output of the spur gear pump is
directly proportional to its
rotational speed
types of HP fuel pump
- plunger
- spur gear type fuel pump
controls the fuel
flow to the burners for every thrust
setting.
fuel control unit/system
is maintained for a
selected throttle position at all
altitudes and airspeeds.
fixed rpm
A fixed rpm is maintained for a
selected throttle position at all
altitudes and airspeeds. This is
achieved by the ________,
which in turn modifies the fuel flow
to suit the new conditions.
expansion or contraction of the Barometric Pressure Capsule by P1 pressure
receives P1 and P3 information.
It uses information to adjust a fuel
metering plunger which prevents
stall or surge by regulating the fuel
flow during engine acceleration.
acceleration control unit
allows for full power to be selected at
any time without risking a meltdown
in the turbine assembly.
top temperature control unit
are positioned
in the gas stream either within the
turbine assembly or close after it. The
output is used to measure the
temperature at the rear of the
engine.
thermocouple probes
The output of the amplifier drives a
_______ which indirectly controls the
fuel flow to the engine.
solenoid
To prevent compressor casing failure,
the fuel control unit incorporates a
_______ device.
power limiter
receives signals of both intake
pressure (P1), and compressor
delivery pressure (P3).
power limiter
The ratio of P3
to P1 can be found by _______
these signals.
combining
are used to limit
compressor rotational speed in order
to prevent excessive centrifugal force.
rpm limiter
2 methods of rpm limiting
- depends on a shaft speed sensor being sent to an amplifier
- involves hydro-mechanical governor which uses hydraulic pressure as the controlling parameter
controls the flow of
fuel between the fuel control unit
and the fuel spray nozzles in the
combustion chambers.
HP fuel cock
is the control normally used for
starting or stopping the fuel supply
to the engine.
HP fuel cock
Two types of electronic engine
control, which enable better fuel
economy, better reliability, and
prolonged engine life, are currently in use. They are:
- Supervisory Engine Control System
- Full Authority Digital Engine Control System
uses a computer which
receives inputs of various engine
operating parameters and controls a
standard hydro-mechanical fuel
control unit.
supervisory engine control system
It monitors EPR, throttle lever angle,
Mach No., engine intake pressure,
and temperature, and will remain a
constant thrust regardless of
changes in air pressure, temperature,
or flight environment.
supervisory engine control syste
receives all necessary
data for engine operation and takes
over virtually all of the steady state
and transient control functions,
which includes compressor airflow
control.
full authority digital engine control system (FADEC)
will prevent engine
limitations being exceeded, and
controls the engine in response to
the throttle lever position.
full authority digital engine control system (FADEC)
devices on fuel control unit/system
- altitude control
- acceleration control
- top temperature control
- power limiter
- rpm limiter
- HP fuel cock
- electronic engine control
- supervisory engine control system
- full authority digital engine control system (FADEC)
have the task of
atomizing or vaporizing the fuel to
ensure that it is completely burnt.
fuel spray nozzles
At engine start, when there is a low
RPM and low fuel pressure, the fuel
spray pattern forms what is known as
a _______. This spray pattern does not
atomize the fuel jet sufficiently for
ignition to occur.
bubble
As the engine accelerates, the pump
rotates faster and builds up more
pressure until the spray pattern
forms a
tulip shape
these effectively use an orifice of variable
size. At low pressures, a pressurizing
valve closes off the main fuel feed to
the nozzle, the only supply coming
from the primary fuel line.
duplex and duple spray nozzles
feeds the
primary orifice which is capable of
providing a finely atomized spray at
lower fuel pressures.
primary fuel line
When the engine accelerates during
start, _______ builds until the
pressurizing valve starts to open. This
allows fuel to flow through the main
orifice, where it supplements the
spray from the primary orifice.
fuel pressure
Gas turbine engines are powered by
________ because it was more
available than gasoline.
kerosene
After the war, the United States Air
Force started using a fuel in gas
turbine engines which spanned the
gasoline and kerosene boiling ranges.
This fuel was called the ________
which stemmed from catalyzing
process from which the fuel could be
taken.
wide cut fuel
this wide cut fuel is still available in
some parts of Alaska and Canada,
because it is suited to cold climates.
Jet B
In the remainder of North America,
this kerosene-type fuel is
used because of its lower cost and
better availability.
Jet A
In the rest of the world, this kerosene-type fuel,
predominates. It has a higher
freezing point than Jet A, which
makes it suitable for use on long
international flights.
Jet A-1
advantage of Jet A-1 over Jet A fuel
It has a higher
freezing point than Jet A, which
makes it suitable for use on long
international flights.
Eastern Europe use ________, which is also a light kerosene-type fuel.
Russian fuel, TS-1
