40 Questions
What is the purpose of a vent system in a light aircraft?
To maintain a positive internal pressure inside the fuel tank
What is the function of the vent openings pointing in the direction of flight?
To prevent fuel tank collapse
What is the purpose of a vent line in an aircraft?
To vent air from the tank
What is shown in Figure 19?
A multi-tank fuel system
What is the purpose of the inwards and outwards relief valves?
To vent air from the fuel tank
What is a disadvantage of jettisonable tanks?
They have minimal protection in a crash or from enemy fire.
What is the location of the vent ports in a multi-tank fuel system?
At the wing tips
Why are integral fuel tanks preferred over rigid tanks?
They use the maximum amount of space for the minimum amount of weight.
Where are integral fuel tanks typically located?
In the wings of the aircraft.
What is the function of the vented filler cap?
To vent air from the fuel tank
What is the benefit of maintaining a positive internal pressure inside the fuel tank?
It prevents fuel tank collapse
What is used to seal the rivets and nut plates in an integral fuel tank?
Sealant.
What is the purpose of access panels in an integral fuel tank?
To allow for easy maintenance and inspection.
How are the covers of access panels in an integral fuel tank typically made fuel-tight?
By using seals or sealant.
What is a disadvantage of jettisonable tanks in terms of aircraft performance?
They restrict the aircraft's performance due to bulkiness and increased drag.
Why are jettisonable tanks not suitable for all aircraft?
They require a large open space in the aircraft structure.
What is the purpose of the amplifier in a capacitance type fuel quantity indicator?
To increase the amplitude of the electric signals
What affects fuel density and thus capacitance of the tank units in a capacitance type fuel quantity indicator?
Temperature variations of the fuel
What is the purpose of the magnetic measuring stick?
To measure the fuel level
How does the latching cam on the bottom surface of the wing tank work?
It is turned a quarter of a turn
What happens when the magnet on the measuring stick is attracted to the magnet in the float?
The measuring stick is pulled down
What is the purpose of the drip stick?
To measure the fuel level
What happens when the drip stick is pulled down to the top of the fuel in the tank?
Fuel enters the top of the stick and runs down to a small drip hole
What is the purpose of unlocking the sealing cap on the drip stick?
To unlock the sealing cap to allow fuel to enter the stick
What is the purpose of the cross-feed manifold?
To connect the refuelling manifold to the desired tank
What is the function of the defuel valve?
To connect the cross-feed manifold to the refuelling manifold
What is the purpose of fuel pressurisation transfer?
To transfer fuel from the auxiliary tank to the main tank
What type of aircraft mainly uses fuel pressurisation transfer?
Fighter aircraft
What type of valve is required in fuel tanks that use pressurisation?
Relief valve
What is the purpose of the jet pump in the fuel transfer system?
To transfer fuel from the auxiliary tank to the main tank
What is used to move the fuel into the main tank in the jet pump system?
Motive flow of fuel from the boost pump
Why is fuel pressurisation transfer mainly used on fighter aircraft?
Because it eliminates the need for transfer pumps
What does the term 'clear' refer to in the context of fuel inspection?
The absence of any readily visible sediment or entrained water
What is indicated by cloudy looking fuel or a slug of water at the base of the glass inspection jar?
The presence of water
Why may the initial sample taken from an aircraft fuel tank drain point contain a high concentration of water and sediment?
The aircraft has been idle for a long time
What is the purpose of sampling until the fuel sample meets the specified requirements of purity?
To meet the specified requirements of purity
What method is used to test for water contamination in aircraft fuel?
Either the glass jar method or the Shell water detection kit method
What is visually inspected during the glass jar method?
Colour, appearance, and water particulate contaminants
Why is it important to thoroughly clean and flush the sampling jar before use?
To prevent contamination of the fuel sample
What is not related to the natural fuel colour?
Clear and bright
Study Notes
Jettisonable Tank Disadvantages
- Minimal protection in a crash or from enemy fire
- Restrict an aircraft's performance due to bulkiness and/or increased drag
Integral Fuel Tanks
- Use maximum space for fuel with minimum weight
- Wing structure is sealed to form a fuel tank
- Leading edge portion of the wing is sealed at both ends and along the spar with fuel-resistant sealant
- Rivets and nut plates are sealed, and sealant is used around inspection openings
- Access panels, hand holes, and tank connections are included at strategic positions
Venting Systems
- Simple venting system: hole drilled in fuel cap or tube running from top of fuel tank to outside of aircraft
- Vent systems have vent openings pointing in the direction of flight to maintain positive internal pressure
- Venting provided through inwards and outwards relief valves
- Vented air flows in and out through vent ports at wing extremities
Multi-Tank Vent Systems
- Vent lines and vent relief valves are used to vent fuel tanks
- Venting modifies current flow to reflect temperature variations of fuel, affecting fuel density and capacitance
Fuel Quantity Indicators
- Capacitance type fuel quantity indicator uses an amplifier to increase the amplitude of electric signals
- Electric signals move the drive motor in the analogue indicator
Magnetic Measuring Sticks
- Used to gauge amount of fuel in a tank manually
- Magnet on the measuring stick is attracted to the magnet in the float
- Fuel level is read on the measuring stick
Drip Stick
- Used to measure fuel level by fuel dripping from the hollow measuring stick
- Fuel enters the top of the stick and runs down to a small drip hole at the base
Fuel Cross-feed Manifold
- Connected to the refuelling manifold via the defuel valve
- Refuel valves can transfer fuel to the desired tank/s
Pressurisation Fuel Transfer
- Uses engine compressor bleed air to increase pressure in fuel tank air space
- Increased air pressure forces fuel to feed into a tank where lower pressure exists
- Fuel tanks must have inwards and outwards relief valves to prevent tank damage
Jet Pump Fuel Transfer
- Jet pump automatically transfers fuel from auxiliary tank into main tank
- Uses motive flow of fuel from the boost pump to move fuel into the main tank
Fuel Sampling
- Initial sample may contain high concentration of water and sediment
- Sampling must continue until fuel sample meets specified requirements of purity
- Water test kits are available to test for water contamination
- Water detection can be performed by glass jar method or Shell water detection kit method
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