11.10 Fuel Systems Flashcards
What are the four main types of turbine engine fuels
Jet A1
Jet A
Jet B
JP 5
What is the flash and freezing point of Jet A1 fuel
38 degrees C
-47 degrees C
Flash and freezing point of Jet A
38 degrees C
-40 degrees C
Flash and freezing point of Jet B fuel
- 20 degrees C
- 58 degrees C
Main requirements of turbine engine fuels
Low freezing point and flash point low enough to provide good ignition capabilities but high as possible for safe fuel handling
At a temperature of 15 degrees C what is the density of Jet A1 and Jet A fuel
0.81kg/ltr
Density of Jet B at 15 degrees C
0.78kg/ltr
What requirements are their for fuel characteristics? (3)
✈️Adequate lubrication
✈️low tendency to hold water
✈️widely available worldwide
What are the dangers of water in fuel and fuel tanks? (6)
- Encourages ice build up
- Supports corrosion
- Engine power fluctuations
- Engine flame outs
- irregular fuel level indications
- Microbial growth in tanks
What is the most common method to test for water in fuel
Syringe test - fuel passes through filter, filter changes colour if fuel contains water
What does the fuel storage system consist of
Fuel tanks
Tank drain system
Tank vent system
Where can fuel tanks be found
Wings
Centre fuselage
Horizontal stabilisers
Cargo compartments
On which aircraft does there have to be space for reserve fuel
All aircraft
What are vent surge tanks used for
Help make sure fuel tanks are properly vented
What purpose do trim tanks serve as well as storing fuel?
Used to trim the Aircraft
What is the most common type of fuel tank used on modern jet aircraft and why
Integral tanks - weight saving
How do integral tanks save weight on aircraft
Parts of the aircraft structure are used as tank walls
How are integral tanks made leak tight
Fillet seal where two plates join and cap seals to cover nuts and bolts
What type of tank has a light metal alloy outer housing and a flexible rubber bladder
Bladder type fuel tank
How is fuel movement dampened
Ribs in the wing and non sealing divider walls
Why does fuel movement need to be dampened
Fuel splashing around during attitude changes would make the aircraft unstable
What does a flap baffle check valve ensure
There is enough fuel for the fuel boost pumps by preventing fuel from flowing out of the collector box
What provides the metal contact between the access door and aircraft structure?
Knit Aluminium Gasket
What is the role of the clamp ring
Connects the access door to the wing structure and ensures mounting screw forces are equally distributed on the seals
How is a tank ventilated
Air is passed through the tank, which is then released into the atmosphere
What is used to indicate if there has been a leak or not
Spur pipe - leak monitor
What are the 2 types of drain valve
Direct and indirect drain valves
Which drain valve is installed at the lowest point of a tank
Direct drain valve
Where might you find find electrically operated drain valves
Stabiliser tanks
What are water scavenge systems used for
Remove water that is collected in tanks
Where might you find water scavenge systems installed
Big fuel tanks - large quantities of water can be expected
How is ram air used to reduce the tendency for fuel to vaporise
Air creates a small positive air pressure on top of the fuel surface
What happens to fuel caught in the vent duct
Drained back into the tanks
What is found inside the vent surge tank
NACA intake and Overpressure relief valves
Where is the NACA inlet located on the Aircraft
Lower wing surface
What are the overpressure relief valves made up of
Either carbon discs (break at certain pressure) or Spring loaded valves (open if differential pressure overcomes spring force)
What are the 2 types of refuelling
Gravity and Pressure refuelling
What is the main disadvantage of of gravity refuelling
Takes a long time
Which tanks do not have external filler ports and how are they refuelled
Centre tank and stabiliser tank
Refuelled by transferring fuel from main tanks
What are the two methods of pressure refuelling?
Fuel truck (bowser) or underfloor fuel supply system
At what pressure does the fuel get pumped into the the system
50 psi
Why is correct distribution of fuel important
Danger of CofG shifting behind MLG
Structural stresses
Main components of a refuelling system? (5)
- Coupling
- Manifold
- Valves
- Diffusers
- Refuelling control panel
What are the three types of refuelling modes
Manual
Automatic
Override
What happens when refuelling in manual mode
Calculate distribution
Monitor fuel quantities
Operate switches to control refuelling valves
What happens when refuelling in Automatic mode
Fuel quantity control computer takes pre-selected block fuel and works out the correct distribution
Controls refuelling valve
When is override mode used
No electrical power to refuelling valves available
What is the ‘Normal Mode’ and why is it used
Automatic mode
It is safer, reduces workload, stops refuelling when the pre-selected block fuel is reached
Where can control panels be found
Wing leading edge near refuelling couplings
On the fuselage
In the cockpit
What can be found to enable the setting of the required block fuel
Pre-selector
What are the types of adjuster are there for the pre-selectror
Rocker switch, rotary switch or thumb wheel
What are the typical indicators for refuelling
Tank quantity indicators
Total quantity indicators
Refuelling valve position indicators (on some)
Malfunction warning lights
When is electrical power usually supplied to the refuelling system
When the panel door is open