The Trouble with water…
The build-up of water in aircraft fuel tanks is a real and ever present risk. Even though Shell Aviation takes extreme care to ensure that we only deliver on-specification, clean, and dry fuel*, water can enter aircraft tanks when humid air is drawn in via tank vents and condenses during aircraft descent. The build-up of water in aircraft tanks can cause two big problems – ice and microbiological organisms. Lumps of ice and ice crystals can block filters and interrupt fuel flow to the engine.
Microbiological organisms can grow in the water, feeding off the jet fuel. The collection of yeasts, molds, fungi and bacteria can themselves block filters and the byproducts of their growth can damage internal tank coatings leading to corrosion and even cause fuel volume gauges to misread. Shell AeroJet uses Fuel System Icing Inhibitor (FSII), an approved additive that dramatically lowers the freezing point of water, thus preventing ice formation. It also creates an environment that discourages the growth of microbiological organisms.
All aircraft can benefit from these features and, for some, the use of FSII is mandatory. In the past, dosing the additive with pressure-fed cans has been problematic – it is essential to achieve correct dose rates and good mixing and, at the same time, avoid contact with people and other materials such as wing surfaces**