Repsol YPF

Can an aeroplane use JET A-1 as well as AVGAS 100LL?

No, under no circumstances. Turbine engines use JET-A1 whereas piston engines use AVGAS 100 LL.

Can I use automotion petrol instead of AVGAS 100 LL?

Automotion petrol and AVGAS have a very different composition. Automotion petrol should not be used in aeroplanes for a wide number of reasons, from the danger of the engine stopping to the dirtying or corrosion of the engine.

AVGAS has higher percentages of parrafin hydrocarbons which provide it with a greater resistance to preignition and greater stability against the formation of rubbers in storage over longe periods of time.

Automotion petrol has a higher percentage of aromatics added which, despite being useful in takeoff, has negative effects such as low heat on combustion, damage to rubber, a tendency towards preignition and bad working order in poor mixture, whilst in flight.

Automotion petrol has a higher percentage of olefinic hydrocarbons. In AVGAS, its content is limited due to its tendency to form rubbers and also because of its bad working order in poor mixture.

Automotion petrol contains hydrocarburons of higher molecular weight which burn worse, which produces deposits and dirtying with the added risk of the engine stopping.

The Reid steam pressure of automotion petrol is much higher (it may even go up to twice as high) than in that of AVGAS, above all in winter. This excess in volatility may cause a "vapour lock" and the subsequent stopping of the engine.

The use of automotion petrol brings about a risk in detonations which may damage the engine, as well as preignition and engines failures when elevated power is required.

The replacement of automotion petrol is normally very quick for which reason, for its storage, it does not require long-lasting characteristics in its composition. For this reason, after a certain amount of time it will lose a numer of octanes and will form rubber deposits which will tend to stick to inlet and exhaust valves and also in the quantity of the combustion metre of the mixture.

Detergent additives which the automotion petrol have are highly corrosive and, when used continuously, may affect the exhaust valves and internal parts of the engine. By the same measure, these additives make the decanting of water in suspension difficult with the risk of freezing in the filter in high altitude flights.

The specification limits of the automotion petrol are broader, for which the answer to the question is less homogeneous. There is no guarantee of similar results in automotion petrol acquired in different places or moments.

If the inflammation temperature of the JET is 38ºC, is there any danger of aeroplane or airport deposits exploding on hot days with temperatures higher than 40 or 45ºC?

No, none at all.

In order for the inflammation of the combustible to occur, three factors need to be taken into account:

• JET steams (the liquid combustible does not burn, but rather the steam that is generated on its surface)
• a flame or spark with the sufficient energy in order to start the process
• and oxygen (for example from the air) in appropriate proportions.    

There are concentration limits, outside of which the mixture of air product is not explosive, be it because it is too poor in the air, or because it is too poor in the steam of the combustible.

If we eliminate all risks of sparks in the proximity of the JET, inflammation will not occur as in the absence of flames or sparks, the temperature of self-ignition of the JET is between 220 / 240ºC and the possibility of the stored combustible reaching this temperature due only to solar radiation on very hot days is null.

The risks of sparks are:

• Exogenous (due to knocks between metallic surfaces, flames, defective electrical circuits; for example: camera flashes, torches or mobile telephones,...)
• Static electricity (due to differences in electrostatic charges between metallic surfaces which are left close to steam).
• Static electricity produced in the combustible in its movement through pipes or when passing through filters, in decanting, ... and not having been discharged properly.
  

Favourable conditions are produced for combustion when the inflammable element has an elevated specific surface, that is to say, a high proportion of surface of the liquid in comparison with its mass. Therefore, in a place which has JET or spray, this may burn at a temperature of below zero, with sparks, although its flash point may be +38ºC.

For all of this, it is important to distinguish the difference between the risk of the JET reaching the necessary temperature so that the auto-inflammation of the combustible can be produced with the danger of the flame or spark igniting, which has in itself a very high temperature, which is capable of heating a reduced area of combustible steams, although this may be at a very low temperature. This small portion of inflamed steam frees up energy which generates sufficient heat in order to heat up another portion of steam closeby which, with the existing flame, expands the fire to the rest of the steam. The generated heat raises the temperature of the liquid which, because of this, releases more steam and the process continues until the volatilization and inflammation of all the liquid.

What contaminates aviation fuels?

The fuel must, at all times, be free from water, solid particles, surfactant additives and microbiological pollutants.

The fuel distribution from the Refineries to the airports is mainly carried out using multi-product lines. The incorporation of water, solids and other pollutants is therefore inevitable.

For that reason, four different types of pollutant can be distinguished:

• Solid pollutants. The solids come principally from the metal filings and scale from the tanks and pipes and bits of flange joints and machinery, as well as from dust, coming directly from the environment, which enters through the tank's ventilation shaft.
• Free water. Water enters the fuel principally due to the day/night temperature change. The humidity in the air condenses on the walls of the tanks and drops into the fuel. On the other hand, the fuel also releases free water when there is a decrease in temperature.
• Tensoactive agents. Tensoactive pollutants usually enter the fuel when it is flowing through multi-product pipelines from the Refinery to the intermediate storage areas. On the other hand, additives, such as antistatics, also contribute to the presence of tensoactives in the fuel.
• Microbiological pollutants. The most common microbiological pollutants are fungi and mould. They reach the fuel at some point in the manufacturing process or in transportation and remain latent until there are suitable conditions for them to develop.              

Further information