The Oil And Cooling System Flashcards
26.18.2 Explain the differences between aviation gasoline (AVGAS) and motor gasoline (MOGAS).
AVGAS is manufactured under more stringent quality control standards than ordinary MOGAS. AVGAS is more leaded than MOGAS giving it a higher octane (or performance) rating to delay the onset of detonation. AVGAS is less volatile than MOGAS and therefore vapour locks problems are reduced. AVGAS is (in NZ) dyed green, MOGAS is yellow (96).
26.18.4 Explain fuel octane ratings and performance numbers.
Fuels which have the same anti-knock quality as iso-octane are given the rating of 100. The addition of small amounts of tetra-ethyl lead to iso-octane results in a fuel which will provide considerably more power, detonation occurs, than pure iso-octane. Since fuel/air ratio has considerable bearing on the power obtained from fuel, most fuels have a dual performance number.
Eg. 100/130 where the first number is power obtained before detonation with a weak mixture, and the
second number with the use of a rich mixture.
26.18.6 Explain the likely result of using a higher grade, or a lower grade, of fuel than that recommended for a given aircraft.
The use of a higher grade of fuel than recommended increases the chances of spark plug fouling and can lead to corrosion of the exhaust valves and seats. The use of a lower grade of fuel than recommended increases the risk of detonation, particularly at high power settings. Aged fuel loses anti-detonation qualities so its performance number falls. The use of a lower grade of fuel than that specified is prohibited.
26.18.8 Explain the caution against using automobile fuel (MOGAS) in an aircraft engine, unless specifically authorized.
MOGAS is not subjected to the same strict degree of quality control as AVGAS. MOGAS is more volatile than AVGAS and vaporizes more readily and therefore is more likely to cause vapor locks in the fuel system. MOGAS can also cause a low power output, spark plug fouling and a strong possibility of detonation.
26.18.10 Describe the distinguishing features of aviation turbine fuel (AVTUR/Jet A1).
AVTUR/Jet A1 is straw coloured or clear and has a distinctive smell of kerosene.
26.18.12 State the difference between the decals used on AVTUR and AVGAS fueling equipment.
AVGAS pump equipment has AVGAS decals or the octane rating (100/130) with white letters on red background. AVTUR pump equipment has AVTUR decals with white letters on black background.
26.18.14 Explain the precautions which can be taken to avoid fuel contamination with water and other impurities.
The most common fuel contaminant is water. Water can be present in the ground tanks, it can also enter via fuel caps, or simply by the air in the tanks condensing. Having full fuel tanks overnight, or if the aircraft is not being used for some days, will minimize condensation occurring.
26.18.16 Explain the special precautions which must be taken when fueling from drumstock.
Fuel in drums can easily be contaminated with water, dirt or rust flakes. When refueling from drums,
pumping equipment should be fitted with an approved in-line filter to remove any moisture and particulate matter. Always check that the drum stock is the right type and grade of fuel and check expiry.
26.18.18 Explain the reasons for the avoidance of non-approved plastic containers.
Storage of fuel in plastic containers is only permitted when those containers have been approved for
this use. It is dangerous to use plastic containers which have not been approved, even if they are of
convenient size and appear to be suitable.
