12.16. Fuel

The hydrocarbon product burned to provide power in an internal combustion engine.

12.16.8. State the common fuel contaminants and the precautions which can be taken to avoid them. 

Most common contaminant is water
– full tanks overnight if in cold weather will minimise condensation
– rust, sand, dust and micro organisms can also cause contamination.
– it is important to filter fuel when refuelling.

12.16.6. State the precautions regarding the use of MOGAS in aero-engines.

– mogas should not be used in an aircraft engine unless its use is authorised.
– more prone to vapour lock, plug fouling and detonation.

12.16.4. Distinguish between the different characteristics of AVGAS, MOGAS andAVTUR (Jet A1). 

AVGAS -(aviation gasoline)
– more leaded than MOGAS – with higher octane / performance rating
– less volatile than MOGAS – safety enhancement (reduces vapour lock tendencies at high altitudes.)
MOGAS – (ordinary motor gasoline)
AVTUR – (aviation turbine fuel)
– straw coloured or clear and smells of kerosene
– not to be used in piston engines

MOGAS in aero-engines
– MOGAS hasn’t the same degree of quality AVGAS which is manufactured to strict quality control standards
– is more volatile than AVGAS
– can cuase vapour locks and fuel starvation in the system
– can cause a lower power output, fouling of the spark plugs and string possibility of detonation

12.16.2. State the common types of fuels and their colour identification.

Different grades of fuels are colour coded

MOGAS
91 = purple
96 – yellow

100LL – Blue
100/130 – Green
115/145 – Purple

12.14. Fuel Injection

A system of introducing fuel to a motor by means other than the pressure drop through a venturi (carburettor)

12.14.8(c) . fuel injectors. 

– with indirect injection, fuel injectors spray the fuel into the inlet manifold.
– with direct injection fuel injectors spray fuel directly into the cylinder.

12.14.8(b) . fuel distribution system; 

– fuel is distributed through a fuel control unit which senses throttle postion, mixture setting and airflow the meter the correct amount of fuel to the injectors.

12.14.8(a) . fuel delivery pump system; 

– most systems have a fuel pump and a boost pump system.
– as well as being a back-up, the boost pump is used the prime the engine for starting and preventing vapour lock problems.

12.14.8. State the purpose of the following components in a basic fuel injection system: