Proficient Pilot

Fuel management

April 1, 1998

An engine fails for one of four reasons. The first is component failure, which, thankfully, is relatively uncommon. Critical components ordinarily do not break when engines are maintained and operated with care.

The remaining three reasons involve depriving an engine of spark, air, or fuel. An engine failure caused by an ignition malfunction is rare, primarily due to redundancy. Choking an engine of air is almost always the result of carburetor or induction icing. This, too, is an uncommon cause of power failure. An attentive pilot can usually combat it successfully by applying carburetor heat or selecting the alternate air source (when operating a fuel-injected engine).

The fourth cause of engine failure is by far the most common but also is the most easily avoided: fuel mismanagement. A predictable number of airplanes and lives are lost every year simply because pilots are insufficiently judicious about ensuring uninterrupted fuel flow to the engine.

This is perplexing because the vast majority of engine failures due to fuel exhaustion or starvation are caused by the pilot. Unfortunately, such traumatic events will continue to occur with regularity (but only to the other guy, right?).

Over the years, I have gleaned from experienced pilots some useful advice that I would like to pass along. Hopefully, these tips will be helpful in ensuring that you are never involved in a fuel-related engine failure.

There remains, however, some confusion between fuel starvation and exhaustion; they are not the same. Starvation occurs when an engine is deprived of fuel while there is still some available (usually in one or more unselected tanks). Exhaustion means that all fuel has been depleted.

A recent study concluded that adopting the following procedures and advice could prevent the majority of fuel-starvation accidents:

  • During every preflight inspection, determine that all fuel vents are clear of obstructions. A clogged vent can result in reduced air pressure in the fuel tank(s) and eventually inhibit flow to the engine. Should this occur, switch to another tank, regardless of the quantity remaining in the original tank, and land as soon as practical. A clogged vent could eventually affect the second tank as well.
  • Personally determine the fuel quantity in each tank, as well as its type and purity. Never take the word of another — important advice for those who rent.
  • The before-takeoff checklist for most aircraft suggests selecting the fullest tank during runup. This, however, might be too late. Instead, select the appropriate tank before engine start and use it exclusively for taxi, runup, and departure. This affords a longer opportunity to test the integrity of fuel flow from that tank. Switching tanks shortly before takeoff does not provide that luxury. You can, shortly before takeoff, select a tank with impeded fuel flow to the engine and have just enough in the lines to only get off the ground before the engine fails.
  • When selecting fuel tanks (at any time), note the integrity of the detents. A worn detent, or an excessively easy or difficult-to-move selector-valve handle warrants maintenance.
  • Speaking of detents, do you know what happens to fuel flow when the fuel selector is placed halfway between two tanks or halfway between a tank and the Off position? It might take awhile, but in most aircraft the engine will sputter, stammer, and then stop.
  • Switch tanks en route only when within gliding range of an airport with long runways, just in case.
  • Do not rely on memory to change tanks. Instead, purchase a battery-powered timer/alarm clock. They are small, inexpensive, and available in many pilot-supply shops. The alarm beeps so loudly and persistently that it can be heard in the cockpits of truly noisy aircraft. Use it as a reminder to switch tanks at predetermined times. You might be amazed at how many accidents result from pilots' failing to switch to the fullest tank prior to an approach and landing. This indicates that many pilots fail to use a before-landing checklist.

Two years ago, I mentioned in this column one of my early instructors who drummed into me that there was absolutely no excuse for running out of gas. He obviously was right, even though numerous pilots offer excuses for doing so every year.

If they are honest, pilots interviewed after experiencing fuel exhaustion usually admit that they had become uncomfortable about their remaining fuel quantity some time prior to fuel exhaustion; it rarely comes as a surprise. Preventing such a trauma, therefore, can be more the result of a state of mind than a calculation of fuel remaining.

When any doubt develops about whether a pilot has sufficient fuel to reach his destination, that is the time to plan for a landing at an alternate airport irrespective of how much inconvenience this might cause. It should not matter that this might necessitate an extra night en route, missing an important engagement, and so forth. Imagine the consequences of a fuel exhaustion accident. And then ask yourself how much inconvenience you might endure in order to avoid destroying your airplane and harming your passengers.

Do this and you'll never run out of gas.