Fuel Tanks - AVGAS Water Contamination - AVGAS Water Contamination

Getting airborne was easy. It was the forced landing 15 minutes later that sent the adrenaline flowing into this pilot's blood. At the first sign of rough running, carb heat seemed to work..., then I lost all power except a very faint idle. I picked out a field and made a forced landing. The next day they found ice in the fuel filter and sediment bowl; in fact, the wing tank drains were frozen and there was ice in the bottom of both tanks.

The aircraft was parked on the ramp throughout the winter. After most flights it was left with fuel tanks less than half full. On this aircraft type as on many others the fuel caps are recessed below the wing surface, leaving space for the collection of rainwater. Removal of the cap without first drying out this recess would permit water to dribble into the tank. In addition, the tank cap seals were in poor condition. The night before the incident the aircraft had been towed into a heated hangar for repairs and by flight time it was thawed out. The rapid change in temperature and exposure to the elements resulted in a build-up of water from condensation and seepage. After refuelling, the stirring action in the tanks will put the water in suspension; before draining the sumps wait a few minutes for any water to settle.

Originally Published: ASL 1/1998
Original Article: Fuel Tanks - AVGAS Water Contamination