Switching Fuel Tanks

Source: Wally Moran

Subscriber question:

"What are the safe procedures for switching fuel tanks in low wing aircraft? What are the dangers of running one tank dry?" - Henry W.

Wally:

"I believe that every time you switch fuel tanks, you cause a slight increase in the probability of having an engine failure.

So, for example I never switch tanks just prior to take off. I always take off on the tank I did the run up on. I never switch tanks at low altitude, like in the pattern. Enroute, I try not to switch tanks unless I am within gliding distance of an airport.

Why am I so cautious? I have seen a fuel selector valve come off as a pilot was switching tanks. Then there is always the possibility of an internal failure in the fuel valve. So why put yourself at risk if you can avoid it.

What about running a tank dry?

I think it is a silly risk to actually starve your engine of fuel to the point it begins to shut down, allegedly to get all the fuel out of the tank. First of all, since you cannot predict the precise moment it will happen, it could happen at a bad time. Further, if there is any contaminates in the fuel they will be in the bottom of the tank so now they are in your system.

In addition running out of fuel and restarting at high power can't be any good for the engine and it scares your passengers. If you have such a tight fuel plan that you require those last drops, you have already made a lot of poor decisions in my view."

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