Millions of litres of jet fuel are put into turbine-powered aircraft every day. One of the things that operators try to ensure is that their fuel is free from contamination. Contaminated fuel can cause significant damage to the aircraft and engine. Damage can range from fuel system corrosion, clogging of fuel filtration components, failure of aircraft fuel system instrumentation, and even stopping the fuel supply to the engines during flight. But with proper procedures in place, you can help prevent contaminated fuel from causing problems to your aircraft.
Jet fuel’s composition allows water to be easily absorbed and held in suspension. Water can be present as suspended particles in the fuel and in liquid form. The amount of suspended particles varies with the temperature of the fuel. Whenever the temperature of the fuel decreases, some of the water particles that are suspended in the fuel are drawn out of the solution and slowly accumulate at the bottom of the fuel cell. However, whenever the temperature of the fuel increases, it draws moisture from the atmosphere to maintain a saturated solution. Therefore, temperature changes result in a continuous accumulation of water.
Water can promote corrosion in fuel system components. If enough water is present, it can form ice crystals in low temperatures and clog fuel lines, filters, or components. This could disturb or even stop the fuel supply to the engine.
If water is allowed to remain in fuel, it will culture micro-organisms or bacteria that feed on the hydrocarbons in the fuel, thereby degrading the fuel quality. These organisms are the next topic of contamination – microbial growth.
Certain bacteria and fungi are capable of existing in the water where it interfaces with the fuel. These microorganisms use alkanes and additives in fuel as foodstuff. These microbes can propagate rapidly. The by-product is a sludge-like substance. In sufficient quantity, this can cause corrosion on steel and aluminum surfaces and attack rubber fuel system components. It can also foul filters and system instrumentation.