Fuel System Flashcards
What components prevent fuel surging about in flight in tanks?
Baffles
What do baffles do?
Prevent fuel surging about in-flight
What is higher up? Fuel supply line or fuel sump?
Fuel supply line
Why is the fuel supply line not at the bottom of a fuel tank?
To prevent impurities that have collected at the bottom being fed into the engine
What is the result of having a fuel supply line not at the very bottom of a fuel tank?
There will always be an unuseable quantity of fuel
How is unuseable fuel possible?
Fuel supply line is above the fuel sump
What is necessary for atmospheric pressure to be maintained in fuel tanks?
Fuel vents
What do fuel vents do?
Retain atmospheric pressure in fuel tanks
What would happen if the pressure in a fuel tank reduced?
Reduce the fuel flow rate and cause the tanks to collapse inwards
Reduction of the fuel flow rate and tanks collapsing inwards is a result of what?
Reduced pressure in fuel tanks (and insufficient venting)
What component alleviates increased pressure in fuel tanks?
Overflow drain
What do overflow drains do?
Alleviate excess pressure in fuel tanks
When does fuel NOT pass through a carburettor?
When the engine is primed
Locking the fuel primer in-flight prevents what?
The cylinders receiving excessive fuel and thus failing due to too-rich a mixture
What might cause an engine to receive excessive fuel if the mixture control is set correctly?
Fuel primer is not locked
What should be done to the throttle if re-starting the engine due to incorrect fuel selection?
It should be closed to prevent a power surge
Why should the throttle be closed when re-starting an engine after incorrect fuel selection?
To prevent a power surge
What component purges the fuel lines of vapour?
Fuel boost pumps
Fuel boost pumps are also known as?
Auxiliary pumps
Auuxiliary pumps are also known as?
Fuel boost pumps
What component is used for simple fuel quantity indicators?
A float
Electric fuel quantity indicators often use what electrical system?
DC
How do electric fuel quantity indicators operate?
Float movement correlates with a variable resistor, changing the current flowing to a gauge
Current alters a magentic field, moving a pointer in the gauge
What aspect of a gauge is altered in an electric fuel quantity indicator?
A magnetic field
What kind of gauge is often used for fuel pressure indicators?
Bourdon tube gauge
What shape is a Bourdon tube gauge?
āCā shape
How does a Bourdon tube gauge operate?
Fluid enters the fixed end
Pressure change will move the free end of the tube
A pressure increase in a Bourdon tube will do what?
Straighten the tube
A pressure decrease in a Bourdon tube will do what?
Curve the tube
Why is Bourdon tube gauge appropriate for light aircraft fuel systems?
The gauge is in close proximity to the engine
What is often used for fuel flow gauges?
Existing pressure gauge that is calibrated to show fuel flow
A fuel pressure gauge can also be recalibrated to indicate what?
Fuel flow
What is an important facet of fuel flow gauges in fuel-injected systems?
A blocked fuel injector will incorrectly read a higher fuel flow
Why does a blocked fuel injector incorrectly read a higher fuel flow in light aircraft systems?
Fuel flow is measured by fuel pressure, so a blockage results in a higher pressure (and thus fuel flow indication)
What colour is Kerosene?
Straw
What fuel is straw-coloured?
Kerosene
100LL AVGAS is what colour?
Blue
Blue-coloured fuel is usually what fuel grade?
100LL AVGAS
What is added to higher octane fuels to improve anti-detonation qualities?
Lead
Why might lead be added to a fuel?
Improve anti-detonation qualities
What does a higher rating/grade of a fuel indicate?
Greater anti-detonation qualities
What does a higher fuel performance number indicate practically?
The power possible (compared to reference fuel) before a rich mixture would detonate
What could occur if using a higher grade fuel than specified?
Spark plug fouling and greater exhaust valve erosion
What causes spark plug fouling and greater exhaust valve erosion?
Use of higher grade fuel than speciified
Kerosene is also known as what?
Avtur
Using motor fuel in an aircraft would cause what?
Lower power output, spark plug fouling and detonation
What is vapour lock?
Vaporisation in fuel lines blocks fuel flow
What is the term given to vaporisation in fuel lines blocking fuel flow?
Vapour lock
What can help minimise fuel tank condensation?
Leaving fuel tanks completely full
What is the advantage to leaving fuel tanks overnight completely ful?
Prevents fuel tank condensation
