Fuel and Water Don’t Mix

Fuel must be handled properly to prevent dangerous contamination.

Last year a large modern airliner was approaching London’s Heathrow when, much to the dismay of the pilots, the engines refused to add that little extra power needed to make the runway.

Exceptional airmanship stretched the resulting glide over the inevitable highway cut (airports after all are large flat areas surrounded by obstacles) so the aircraft ended short of the runway but on the flat so everyone survived. This is not a critique of that accident, save this: After much tortuous investigation and testing, the suspected culprit was some ice collecting on the inlet of the fuel-cooled oil cooler, thus restricting the supply of fuel to the engine. It must be admitted that it took the extreme conditions found at a very high altitude and very long-range operations over the far north to bring this about. Modifications to the engine fuel system are in the works to prevent this.

I have over the years had the responsibility of writing the technical manuals for several airlines. A fair bit of the material in those manuals involves the care and handling of the fuel that goes into the aircraft. There is a lot of information out there when you research it. The fuel companies are always helpful with material concerning fuel specifications and the handling of fuels. They will eagerly share it with you. This is a god-send when you are involved with overseas operations into Russia and its former republics and in parts of Asia. It can be quite fascinating to read the fuel specs.

The airline auditors then have to go to these far-off places and see that the vendors comply with the manuals.

One of the things that comes up time and time again is that water will get into fuel at different stages of its handling and it is up to the supplier and operator to make sure it gets removed before it gets into the aircraft. Also it is important to remove it from the aircraft tanks because the simple fact is, as you burn fuel from a tank, the air venting in will have moisture in it. This will inevitably condense on the cold tank structure and enter the fuel supply. Regular sumping of the aircraft will detect it and prevent future bacterial growth in the tanks. No one, however, has come up with a good way to do this in frigid conditions.

Fuel quality control has improved over the years. On the other hand, aviation gasoline did not hold water as easily as the kerosene blends we now use. Water settles out of gasoline faster than it does from kerosene for one thing and, to a certain extent, the lead and other additives tended to inhibit the formation of the nasty slimes and bacteria that so like kerosene. Then too much of the fuel was delivered to the airport by truck and barge and not in the usual sealed pipelines we have today. Some airports were really tight on fuel storage and it was literally hand-to-mouth at LaGuardia Airport, which depended on barge-loads of fuel to keep it supplied. An uncle of mine at American described how they were literally praying the tug captain could get the barge through the ice one cold winter before they ran out of fuel. Obviously, too, bringing in fuel by barge is another means for water to get in the fuel.

A Lesson learned
Up in Boston, Eastern had an underground tank farm behind its hangar. Fuel was delivered to it by tank truck. I asked why they had never hooked up to a pipeline for the fuel supplier was nearby. I was shown a pit on the edge of the tank farm. On one side was a pipe protruding from the wall with a cap over it. Opposite was another capped pipe. Three feet separated them. One line led to the fuel supplier. The other line led into our tank farm. Some long ago dispute between the airline, airport authority and suppliers prevented the hookup and so there was a regular parade of tank trucks delivering the fuel. With the shuttle operation and regular system, flights that was a lot of fuel.

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