AFS Topic 2 EASY

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Questions and Answers

What is the purpose of a vent system in a light aircraft?

To reduce the weight of the aircraft

To reduce fuel consumption

To maintain a positive internal pressure inside the fuel tank (correct)

To increase the speed of the aircraft

What is the function of the vent openings pointing in the direction of flight?

To improve aircraft stability

To reduce air resistance

To increase fuel efficiency

To prevent fuel tank collapse (correct)

What is the purpose of a vent line in an aircraft?

To vent air from the tank (correct)

To drain fuel from the tank

To increase fuel pressure

To reduce fuel evaporation

What is shown in Figure 19?

A multi-tank fuel system Signup and view all the answers

What is the purpose of the inwards and outwards relief valves?

To vent air from the fuel tank Signup and view all the answers

What is a disadvantage of jettisonable tanks?

They have minimal protection in a crash or from enemy fire. Signup and view all the answers

What is the location of the vent ports in a multi-tank fuel system?

At the wing tips Signup and view all the answers

Why are integral fuel tanks preferred over rigid tanks?

They use the maximum amount of space for the minimum amount of weight. Signup and view all the answers

Where are integral fuel tanks typically located?

In the wings of the aircraft. Signup and view all the answers

What is the function of the vented filler cap?

To vent air from the fuel tank Signup and view all the answers

What is the benefit of maintaining a positive internal pressure inside the fuel tank?

It prevents fuel tank collapse Signup and view all the answers

What is used to seal the rivets and nut plates in an integral fuel tank?

Sealant. Signup and view all the answers

What is the purpose of access panels in an integral fuel tank?

To allow for easy maintenance and inspection. Signup and view all the answers

How are the covers of access panels in an integral fuel tank typically made fuel-tight?

By using seals or sealant. Signup and view all the answers

What is a disadvantage of jettisonable tanks in terms of aircraft performance?

They restrict the aircraft's performance due to bulkiness and increased drag. Signup and view all the answers

Why are jettisonable tanks not suitable for all aircraft?

They require a large open space in the aircraft structure. Signup and view all the answers

What is the purpose of the amplifier in a capacitance type fuel quantity indicator?

To increase the amplitude of the electric signals Signup and view all the answers

What affects fuel density and thus capacitance of the tank units in a capacitance type fuel quantity indicator?

Temperature variations of the fuel Signup and view all the answers

What is the purpose of the magnetic measuring stick?

To measure the fuel level Signup and view all the answers

How does the latching cam on the bottom surface of the wing tank work?

It is turned a quarter of a turn Signup and view all the answers

What happens when the magnet on the measuring stick is attracted to the magnet in the float?

The measuring stick is pulled down Signup and view all the answers

What is the purpose of the drip stick?

To measure the fuel level Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is the purpose of the cross-feed manifold?

To connect the refuelling manifold to the desired tank Signup and view all the answers

What is the function of the defuel valve?

To connect the cross-feed manifold to the refuelling manifold Signup and view all the answers

What is the purpose of fuel pressurisation transfer?

To transfer fuel from the auxiliary tank to the main tank Signup and view all the answers

What type of aircraft mainly uses fuel pressurisation transfer?

Fighter aircraft Signup and view all the answers

What type of valve is required in fuel tanks that use pressurisation?

Relief valve Signup and view all the answers

What is the purpose of the jet pump in the fuel transfer system?

To transfer fuel from the auxiliary tank to the main tank Signup and view all the answers

What is used to move the fuel into the main tank in the jet pump system?

Motive flow of fuel from the boost pump Signup and view all the answers

Why is fuel pressurisation transfer mainly used on fighter aircraft?

Because it eliminates the need for transfer pumps Signup and view all the answers

What does the term 'clear' refer to in the context of fuel inspection?

The absence of any readily visible sediment or entrained water Signup and view all the answers

What is indicated by cloudy looking fuel or a slug of water at the base of the glass inspection jar?

The presence of water Signup and view all the answers

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 Signup and view all the answers

What is the purpose of sampling until the fuel sample meets the specified requirements of purity?

To meet the specified requirements of purity Signup and view all the answers

What method is used to test for water contamination in aircraft fuel?

Either the glass jar method or the Shell water detection kit method Signup and view all the answers

What is visually inspected during the glass jar method?

Colour, appearance, and water particulate contaminants Signup and view all the answers

Why is it important to thoroughly clean and flush the sampling jar before use?

To prevent contamination of the fuel sample Signup and view all the answers

What is not related to the natural fuel colour?

Clear and bright Signup and view all the answers

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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