13.13 Fuel Systems Flashcards
What are the two types of fuel used in aircraft?
Aviation gasolene – piston
Aviation kerosene – turbo–jet and turbo–prop
What qualities should aviation fuel have?
Easy pump and flow under all operating conditions
Enable engine starting at all ground conditions and gives satisfactory relighting characteristics
Efficient combustion under all conditions
High a calorific value as possible
Minimum corrosive effects on the combustion system or the turbine blades
Minimal corrosive effects on the fuel system components
Adequate lubrication for the moving parts of the fuel system
Reduce fire risks to a minimum
What is the identification marking for AVGAS?
Single blue band followed by a red rectangle
AVGAS written in white
What is the identification marking for AVTUR?
Two black bands followed by a black rectangle with JET A–1 written in white
How do antioxidants work and what do they prevent the formation of?
Interrupting the chain of oxidation reactions
Peroxides
Soluble gums
Insoluble particulates
What are ‘chelating agents’?
Chemical compounds that form stable complexes with specific metal ions
How is FSII added to fuel?
The additive must be injected at a controlled rate into a flowing stream of fuel
When will cladosporium resinae propagate in a fuel tank?
When water is present and the temperature is between 15°C and 35°C
At what general geographical zone are conditions favourable to fungal growth in fuel tanks?
30° N to 30° S
What other artificial cause might create the ideal conditions for the growth of Cladosporium Resinae?
Modern heated hangars
What might be the cause of erratic, or false, fuel quantity indication?
Microbiological contamination
What should a refueller deliver line contain?
5 micron filter
In order to meet the requirement of delivering a supply in excess of engine demand under the most adverse operating conditions, what are these conditions considered to be?
Full power at sea level with an almost empty tank
What is ‘surge’ in relation to fuel?
Mass free movement of fuel within a tank
How is ‘surge’ reduced?
Baffles, which allow flow of fuel but reduce ‘surge’
What is a disadvantage of a rigid removable tank?
Tank must be smaller than the tank compartment to fit into the compartment
Best use of the available space is not utilised
What might baffles be called in an integral fuel tank?
Chordal diaphragms
Why are 3–phase AC fuel pumps mainly used in modern aircraft?
High flow rates that can be achieved from relatively small pumps
Why is a bypass mechanism not necessary in a LP pump?
Fuel can be drawn through a ‘stationary pump’
What are the two types of LP fuel pump location?
Fully immersed (wet bay)
External (dry bay)
What is the advantage of a ‘Canister Type Pump’?
Failure of the pump does not require draining of fuel tanks
Reduces aircraft down time
On light aircraft, where is the booster pump normally fitted?
Between the tank and the engine
What are jet pumps also known as?
Scavenge pump
Venturri pump
Where is a jet pump normally fitted, and what is peculiar about it?
Remote areas of the fuel tank
No moving parts, instead relying on the motive flow from the booster pump to move fuel
What are the conditions which require fuel venting?
Inflow and outflow of air as the aircraft changes ‘altitude’
Changes in fuel capacity as the aircraft is being ‘refuelled and defuelled’
Changes of fuel contents as the fuel is being ‘used by the engines’
Effects of temperature changes which would cause expansion and contraction of the aircraft fuel contents
Allowance to discharge excess fuel to atmosphere should the refuelling valve fail to close when the tank is filled
How might vented fuel, which collects in the vent/surge tank, be returned to the fuel tanks?
By a continuous ‘jet pump’ operation
or
An intermittent ‘electrically operated pump’ system
What is the purpose of limit switches in the valves of the aircraft fuel system?
Cut off power to the motor at the fully–open and fully–closed positions
May also be used to operate position indication lights or magnetic indicators in the crew compartment
What is energised automatically as the motor is de–energised in a valve in the aircraft fuel system?
A brake
What is the delineation from airframe mounted fuel system from the engine fuel system?
LP cock
If a booster pump fails, how is the engine prevented from being starved of fuel?
Suction created by the engine driven pump will draw fuel through a suction valve directly from the tanks
What is fitted in a non–return valve for an aircraft fuel system to ensure the valve is not fitted the wrong way round?
Interference spider
When would a booster pump for a light aircraft be on?
Starting
Take–off
Climbing
High altitude
Turbulence
Landing
What is the purpose of the transfer valve?
Transfer fuel from one set of wing tanks, to the tanks on the opposite wing
What is the purpose of the inter–engine valve?
Transfer from one set of tanks on a wing, to the engine usually fed by the other tank of the same wing
What is the purpose of the crossfeed valves?
Transfer from the tanks on one wing, to the engine or engines on the opposite wing
Why is there a higher stack pipe on the pump ordinarily used for ‘jettison’ purposes?
To ensure that all fuel is not jettisoned
Where are fuel supplies normally taken for APUs?
Directly from a suitable tank like the horizontal stabiliser
What are the typical delivery pressures and flow rates when refuelling an aircraft by tanker/hydrant?
50 psi
300 gallons per minute
What is the typical suction pressure when defuelling by tanker/hydrant?
11 psi
What is the purpose of a cascade device in an aircraft fuel tank and why is it required during pressure refuelling?
Protect interior of a fuel tank, especially the sealant
A pressurised jet of fuel entering the tank could easily cause damage
How might the operation of a booster pump used for jettisoning be different than normal operation?
Run at a higher speed
How is the fuel feed to the engine protected during jettisoning?
Non–return valves
When are the jettison valves armed where a jettison pipe is used?
When the jettison pipe is locked in the extended position
How is it ensured that no fuel is lost through the jettison pipe when it is retracted?
Jettison pipe forms a seal at the manifold
Handling of fuels can lead to which skin condition?
Dermatitis
What are the two types of removable fuel tanks?
Rigid and flexible
What are the three separate roles that 3–phase AC fuel pumps can be utilised for?
Booster pumps – supplying fuel to engines
Transfer pumps – transferring fuel between tanks
Jettison pumps – jettison
Why might 3–phase AC fuel pumps not require a pressure relief valve?
Fuel will simply recirculate within the pump maintaining a low pressure supply
What are the three mechanical methods of checking aircraft fuel level in the tanks?
Magnetic level indicator
Dip stick
Drip stick
What operates a warning lamp in the crew compartment with regards to the manually controlled fuel heating system?
A pressure differential switch on the fuel filter, which suggests that ice has begun to block the fuel filter
In an automatic fuel heater, what causes the opening and closing of the bleed air valve?
Expansion and contraction of a wax charge
What seal is required in a low pressure coupling?
O ring or rubber seal
How should tanks be ventilated?
Passing dry filtered air through the tank, until all fuel vapours have been removed
Can also be ‘purged’ with CO2
What must a person working in a tank also have?
Lifeline to a person on the outside
Where should fuelling be carried out?
At a place approved by the aerodrome authority
At least 15 metres (50 feet) from any building
Who must supervise fuelling procedures?
Fuelling overseer
Where must No Smoking Signs be situated when refuelling?
At least 15 metres (50 feet) from the fuelling area
Where must GPUs be positioned when refuelling an aircraft?
At least 6 metres (20 feet) from aircraft filling and venting points
What is the limit of seating capacity for which refuelling cannot be carried out with passengers on board?
Seating capacity of less than 20
What is specific gravity?
Weight of a liquid in comparison with that of water
Within the refuelling manifold, what enables the diaphragm to move in order to allow fuel into the tanks?
Solenoid is energised or the manual override plunger is pushed and held
Fuel pressure above the diaphragm is relieved and the fuelling valve opens
What additive is a ‘chelating agent’?
Metal deactivator
What component will be used where a fuel pump is fully immersed in the tank (wet bay)?
Canister type chamber
