Besides the traditional and always educational ‘Preflight challenge’, the General Aviation Safety Council (GASCo) provided a very insightful fuel sampling demo at its LAA Rally stand in late August. “The idea came from a recent accident in which a Rockwell Commander had an engine failure after takeoff due to the presence of water in the tanks”, said Mike O’Donoghue (GASCo’s Chief Executive), as he explained the rationale behind the display. “The pilot may have collected fuel samples, as per the checklist, but did not manage to spot the presence of water”.
The likely problem in that case, GASC0 said, is that pilots often assess only the visual appearance of the fuel, or its smell. For a correct assessment, instead, both techniques should be used. The issue became immediately clear when visitors to the stand were presented with a sample that, in marginal light conditions (imagine a hangar on a cloudy day), looked like avgas, and smelled like avgas. In reality, the sample contained only pure water: the liquid smelled like avgas because the container over time had taken up that smell. The marginal light conditions, in addition, made it easy to confuse the transparency of water with the faint blue that avgas should normally have. The only way to detect water, in this case, would be by using a clear source of light (eg a torch), and assess the colour against a white background. A hasty fuel sampling, instead, would almost certainly not allow a pilot to detect water in this scenario.
PHOTO: Eugenio Facci
