fuel Flashcards
ideal characteristics for fuel
lubricity
flows easily
ease of engine starting
complete combustion
no damage to engine from combustion byproducts
low fire hazard
non corrosive
high calorific value (amount of heat released during combustion)
Energy from fuel is dependent on…
Energy is dependent on mass not volume
Octane
**Measure of fuel’s resistance to detonation when subjected to high pressure **
Fuels for Gas & Pistone engines
Piston Engine - Use Gasoline
1. Avgas (aviation gasoline)
2. Mogas (motor gasoline)
Gas turbine engine - Use Karosene
1. Avtur (aviation turbine fuel)
2. Avtag (aviation turbine gasoline)
AVGAS properties
Aviation Gasoline
Use for Piston engines
labelled in white print and red background
manufactured to conform with DERD 2485 specifications
Use High Octane because Piston engines are high compression engines
AVGAS 100 LL –> Blue –> Low Lead –> 100/130 Performance
Flashpoint -40C / Freezing -58C
AVGAS 100 –> Green –> High Lead –> 100/130 Performance
Flashpoint -40C / Freezing -58C
AVGAS 115 –> Green –> High Lead –> 115/145 Performance
Specific Gravity (density) = 0.72 at 15C
Octane rating
Higher octane is used with high performance engines having high compression ratios
MOGAS
Motor gasoline
used in certain airframe engine combinations
specs: CAP 747 GC2
low octane rating (below 100 octane)
high volatility - causes icing in carburettor - locks vapour
Gas turbine fuels are known as …
kerosene
‘heavier and less volatile than gasoline*
Avtur
For gas turbine engines
avtur (aviation turbine fuel)
Kerosene
JET A1 - SG 0.8 at 15C, flash point 38C & waxing point -47-50C - used worldwide
**Jet A **- SG 0.8 at 15C, flash point 38C & waxing point -40C - used in USA only
Avtag
not used in civil aircraft
avtur (aviation turbine gasoline)
Kerosene + gasoline mix
**Jet B **- SG 0.77 at 15C, flash point -20C & waxing point -60C
**Not used in aviation due to wide range flammability **
colour of gas turbine fuel
straw yellow - colourless
‘natural colour’
not dyed for identification
cloudy fuel indicates…
cloudiness usually indicates presence of water
however…
if cloud ‘rises quickly’ to the top = air
if cloud ‘falls slowly’ to the bottom = water
Jet fuel additives
Fuel is blended with additives in refinary or at the airfiled and storage/transfer
Why?
to improve its operating ability
Types:
FSII (Fuel System Icing Inhibitor)
* To avoid icing and fungus
* Jet A-1 has FSII
* Jet A - does not have FSII
- Icing inhibitor: with altitude, fuel is cooled and water droplets form and crystalize blocking fuel system components
- fungal inhibitor: fungus is always present and grow to form green long filaments that block fuel system components. Byproducts of fungus are also corrosive
HITEC
* Lubricity agent
* reduces wear in fuel system components (pumps, fuel control, etc)
Static dissipater
* **eliminates **harzard of static electricity
* which forms when **fuel flows through ‘high flow transfer system’ during fueling and de-fueling **
corrossion inhibitors
* protect ferrous metals in fuel handling systems
* pipelines, storage tanks
* also improves lubricating quality
Metal de-activators
* supress fuel oxidation caused by some metals
Water in fuel - how to manage it
1. manufacturer quality control & preventative measures
2. water drain:
* when fuel settles after fueling, water droplets sink in the tank and can be drained via water valve
3. Atmosphere exclusion:
* filling tank to full to exclude the atmosphere and avoid contamination with water/moisture.
Fuel heater:
* ice can form at high altitude
* fuel passes through engine heat exchanger with high compressor hot air to heat it and dissolve ice crystals.
* Systems utilize a** fuel cooled oil cooler**, this uses the hot engine oil to warm fuel but also cools the oil (heat exchange)
Waxing
Fuel has hydrocarbons
In low temperature they deposit in the form of paraffix wax cyrstals
To avoid:
- Refinery should keep low levels of hydrocarbons
- keep engine fuel warm
Boiling
- Temperature at which fuel boils varries depending on pressure.
- In climb –> pressure drops –> fuel burns quicker
- vapor is formed in the pipelines
- fuel supply to the engine is cut off –> engine stalls
Solution
* Fuel booster pumps:
* - pressurizes fuel in the pipeline from the tank to the engine -> pushing fuel towards the engine
* - instead of using enging pumps that suck fuel from tanks further reducing pressure
Specific Gravity
Ratio of density of solid/liquid to density of water
OR
weight of liquid / weight of equal volume of water
Specific gravity **varies ‘inversely’ **on temperate
it makes a difference when tank is full and mass of fuel load is taken into account
Fuel quantity measuring system also compensates for changes in Specific Gravitty
Aircraft fuel tank
Integral:
* inside wing, torsion box, horizontal stabilizers
* sealed & light weight
* in modern aircraft with mutli-engine
Rigid: light aircraft
* externally mounted in or on wing tip or fuselage
* heavier due to mounting structure needed
* on light single engine aircraft
* filled overwing method (open line thru filler cap)
* metal or composite construction
flexible
* bag made of sealed rubberized material - fuel bladder
* needs a structure inside the wing/fuselage to mount it
* self sealing in the event of damage
* high performance light aircraft, smaller turboprops, military aircraft
Baffles
On large aircraft/integral tanks
fitted inside the tank to minimize fuel serges from inertial forces generated from heavy maneouvering of aircraft
Baffle check valve
* allow fuel to flow inboard not outboard to wing tip during manoevres
Delivering fuel to the engine..
must deliver more fuel than the engine can possibly use in critical phases to avoid engine starved for fuel
Rigid Fuel systems on light aircraft
Gravity feed fuel system
Pressure pump
Gravity feed fuel system
used on high wing aircraft - single engine
used with tank is high above the carburettor to provide pressure
Single engine piston fuel system
1 ) Rigid L & R tanks in wings
2) filler cap on top of the wing
3) Fuel is drawn from the tank by these steps:
- electric or manual/mechanical fuel pump
- through a hand operated tank selector (allows pilot to choose fuel from right or left tank or turn off supply)
- then through filter
- then through to carubrettor
Piston engine often are primed with fuel before engine start via hand operated priming pump
float operated level sensors
water drain valve
fuel gauges
Multi engine Complex aircraft
Fuel System
tanks
* for extra fuel capacity: –>Integral, wing, central (torsion box), horizontal stabilizers or fin
* to help change aircraft centre of gravity
filler caps
where you connect the open line fueling pipe to
Float level sensor
gauging system
Over pressure relieve valve:
* release pressure in case of malfunction to save the structure of the tank
Baffles
* dampen the rapid movement of fuel during serges in the tank
Fuel water drains
* drain water - in light aircraft
high level float switch
* switch to close the fuel valve when tank is full
low level float switch
* switch to maintain the required minimum fuel in the main tanks during ‘dumping’
cross-feed & shut off valve
* feeds fuel from any tank to any engine
* isolates when there is a fault/emergency
filters
prevent debris in the tank to be drawn into booster pumps
vent system
* vent valves vent surge tank
* equalize pressure above fuel in the tank to equalize with ambient pressure
* provide for ram air to be introduced to partially pressurize the tanks in flight to assist the fuel flow & reduce fuel boiling at altitude
* overflowing fuel is collecdted by surge tank and recycled back to main tank
* vent space is 2% of tank volume
booster pumps
* fitted in pairs in each tank to pump fuel to engine
* driven by AC motor
* provide 20-40 psi pressure
* provide high flow
* needed in high alititude ->prevent cavitation of the engine driven pump
* pressurize fuel in pipelines (to avoid vapor blocking pipeline from boiling fuel)
* if a double booster pump fails in one main tank the ‘Aircraft Minimum Equpment List’ limits the aircraft to a max operating altitude to prevent fuel starvation
collector tank/feeder box
* booster pumps are fitted in this tank
* carries 500kg of fuel
* keeps booster pump submerged to prevent pump cavitation
benefit of split wing tank
- The wing tanks are split into two elements, outer and inner sections
- allow a certain amount of fuel to remain in the outer section until the inner has reached a pre-determined level.
- Keeping fuel outboard in this manner helps to reduce wing bending stress and relieve flutter.
fueling light aircarft
‘overwing’
remove tank filler cap
fuel in gallon or Litres (amount is displayed on delivery vehicle gaugae)
fueling in large aircraft
- **pressure refuelled **
- from hydrants or bowsers through underwing **refuel/ defuel coupling points **
- The quantity required in each tank can be preselected
- the refuel valve will close **when this level has been reached. **
- The **system will prevent **any tank being overfilled.
Controls
and controlled by quantity, tank and valve selection from a conveniently situated refuelling control panel.
Fuel quantity control gague by tank. in Thousand of kg
HIGH LEVEL LIGHTS.
* These come on BLUE when high level switch is sensed and the corresponding refuel valve will close automatically.
3 position Refuel valve switch
* Guarded in normal - tank is controlled by automatic refueling computer
* Open - valve opens when MODE SELECT switch is set to Refuel or Defuel
* In Refuel, each refuel/defuel valve will close when tank is full
* Shut - refuel valve remains closed
Mode swtich
* Off - guarded to off position
* refuel system is de-energized and refuel valve is closed.
* Refuel - refuel valve operate in automatic or manual mose depending on the position of Refuel valve switch
* Defuel - Refuel valves and transfer valve open
** TRF (transfer light)** -
* Amber when transfer valve is open
Test switch
High - illuminate BLUE if high level sensors and associated circuits are serviceable
LTS - lights on panel and all 8’s on fuel quantity indicator illuminate
**Elec Power **
Refuelling or defuelling can be powered by GPU , APU or battery 1
Preselected display
display presenlected fuel qty in kg x 1000
preslector rocker switch: increase or decrease the preselected qty
**Actual **- total fuel on board
auto refuel light - Green (end) when auto refuelling is completed
REFUELLING SEQUENCE
- Press ‘Preselector rocker switch/Preselecdted display’ to preselect the required fuel load
- Ensure all 3 Refuel valves are in Normal
- Select **Mode Selector switch ** to ‘ Refuel’
- Then the automatic refuel system will refuel each tank in the correct sequence to achieve the preselected fuel load
- When refueling is complete - the Preselected and Actual windows will read the same. And Actual display will turn Green (End)
- The Mode Selector switch should be turned on the ‘OFF’ position.
AVTUR
Fueling vehicles / hydrants are labelled…
JetA/JetB/JetB in whilte print on black background
AVGAS
Fueling vehicles are labelled…
AVGAS 100LL/100/130 = white print on red background
Fueling zones
- extend at least 20 ft/ 6 m radius to cover all areas where fuel vapor might expel
* venting points (ie. wingtip)
* filling points
* fueling equipment
Fueling zone restrictions
- NO smoking
- NO photographic flash
- fire extinguishers should be readily availbe
- only authorized people should be allowed in refuelling zones
- personnel #s should be kept to a minimum
- **Ground Power Unit **should be located far and cannot be connected / disconnected during refuelling ops.
- if APU exhaust (which is required for fueling operation) discharges, it must be started before filler caps are removed and fuel connections are made
- if APU stops during refuelling, it cannot be started again till refuelling has ceased and no danger in igniting fuel vapor
Before refuelling
Aircraft should be bonded (connected) to refuelling equipment using dedicated wires and clips - avoid sparks/electric static
NOT allowed to use CONDUCTIVE hoses for bonding
Overwing refuelling
The hose nosel must be bonded to aircraft structure before removing the tanks filler caps
funnels, etc must be bonded to aircraft
Plastic funnels or pipes cannot be used
Underwing fueling
the mechanical metal on metal contact between the nosel end and aircraft fitting eliminates the need for a hose end bonding cable
Precautions relevant to flight crew
If aircraft settles on landing gear -
all ground equipment should be cleared from the underside of the aircraft
Main engine should not be operated
No strobe light
Lamps and light should be ‘flameproof’
**Follow refuelling sequence **to ensure aircraft centre of gravity is maintained - aircraft refuelling manual
readily available fire extinguishers
hazards to look out for
- aircraft cannot be refuelled 30m/100ft from radar equipment
- If landing gear is overheated, no refueling till heat is gone. Fire crew should be in vicinity
- avoid fueling during electrical storms
refueling with passengers on board
cannot fuel with passengers on board if fixed wing aircraft has less than 20 seats
If passengers are boarding/disembarking, they are to be **guided by an official **and their route should be directed
cannot fuel with passengers if AVGAS or JETB is used
once specified person must stay outside in designated area whilst passengers are onboard
- who handles emergency & fire fighting procedures
- handles communication and evacuations procedures
If fuel vapor or other issues detected during fueling. fueling must be stopped
crew & passengers must be warned that fueling is going to take place
seatbelt signs OFF
no smoking sign ON
Interior lighting ON to i**ndicate emergency exists **
Person on board designated for immediate evacuation
Ground area beneath exists must be cleared for evactuation
**ground servicing and work in aircraft **(ie catering/cleaning) **should not be creating any hazard or obstruction **
managing exit doors for evactuation
- at least 2 passenger doors (or 1 main and 1 emergency if only one main exists) ideally at opposite ends of aircraft
For aircraft with automatic inflatable chutes
**1. If loading bridge is used **
* no additional steps need to be provided
* left or right rear door should be manned constantly be crew - can be used for inflatable chute evactuation
2. If loading bridge is not available
* one set of steps should be positioned at 1 main door used for embarkation/disembarkation
For aircraft withOUT automatic inflatable chutes
1. If loading bridge is used
* one set of steps shoudl be positioned at another passenger door - ideally at opposite ends
2. If loading bridge is not available
* two set of steps shoudl be positioned at passenger doors - ideally at opposite ends
3. if aircraft is fitted with integral steps
each may count as one means of exit
When fuelling is complete,
bonding wires (grounding wires) should not be removed until either:
- filler caps have been refitted, or
- the pressure refuelling hose has been disconnected.
APU
APU gets fuel from any tank if booster pump is on
but gets fuel from #1 Tank by the bypass valve if booster pump fails. The APUR has DC electric fuel pump which will switch on automatically
APU shut off valve is operated by automatic start/stop sequence
centre tank scavenging system
when booster pumps can’t pump fuel from centre tank, the residual fuel can be removed to the No 1 tank by use of the scavenging system
fuel usage sequance (norma) at take off
start with central fuel tank first, then the wing tank - relieve wing bending
suck valve in tanks
allow engine to be fed by gravity or suction by the engine driven pump if both booster pumps fail in 1 tank
