OUT OF GAS?!... Statistical studies show us that we can count on at least 10% of aircraft accidents to be caused by fuel exhaustion or fuel starvation. Some models show at least one fuel related accident per week. Of all the causes of airplane accidents, fuel exhaustion related accidents should be the easiest to address followed closely by fuel starvation accidents. If there isn't any fuel - that's exhaustion, if there is fuel but it isn't getting to the engine that's starvation.

The beginning of any successful flight is planning, even if the flight is only for an hour or so "just around the patch". Each pilot should know the fuel consumption rate of the airplane they fly. At a given power setting fuel consumption (time) is a constant and range (distance) is variable. When planning any flight it doesn't hurt to add some to the rate for a margin of safety. How much is going to depend on how well we know our airplane.

When checking the quantity of fuel onboard don't rely only on the fuel quantify indicator. Quoting the Certification regulations for small airplanes: "…(1) Each fuel quantity indicator must be calibrated to read "zero" during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply…" That can be interpreted to mean that the requirements for certification require the indicator to be accurate only at zero or empty. That is no time to find out how accurate our gages are. To ascertain the quantity of fuel in your tank you might make a calibrated dip stick "for your airplane". Using a dip stick from another airplane, even though it may be the same model should be avoided. Not all like models are configured the same and the indications will vary. Some airplane manufacturers put tabs in the tanks to help determine the quantity of fuel. When using any visual method of checking the fuel quantity remember that the airplane needs to be on a level surface for accuracy.

Knowing our airplane's fuel system is as important as knowing how much fuel we have onboard. Is the fuel system gravity fed? (high wing), or pumped? (low wing, high performance, etc.). If your tanks are interconnected can they crossfeed during a refueling? Some airplane manufacturers recommend that the fuel selector be in a specific position to prevent crossfeeding. Others recommend going back to the first tank after filling the second tank. On pressure fuel systems most airplanes will have two fuel pumps, an engine mounted pump and an auxiliary pump. The engine is mechanically driven and the auxiliary pump is usually electrically driven. Normal operations usually only utilize the engine driven fuel pump. The auxiliary pump may be used for priming, high-altitude operations or emergency use. Airplanes without an auxiliary pump generally will incorporate a priming pump. It is important to assure the priming handle is stowed and locked in position before flying. Failure to do so can result in an overly rich mixture because priming fuel is taken from the system before fuel metering by the carburetor. Several airplane manufacturers designed their products to receive fuel from only one tank at a time. If this is the case you should know which end of the fuel selector valve handle points to the selected tank. Using the wrong end of the handle has caused several exciting moments in the lives of aviators.

In my experience, and I am sure that I am not alone, leaning an engine was more self learned than taught. During my flight training I normally did not use a fixed power setting because I was always going from one maneuver to the next. This required constant power changes. And, other than the long cross country flights I had to do, I didn't fly much higher that 3000 to 4000 feet AGL. Sure, my flight instructor discussed the leaning procedures to me but we didn't use them because it wasn't necessary. Failing to lean and keeping the mixture control in the full rich position will not enable us to obtain the endurance performance from the airplane. Performance tables and charts are based on properly leaning the engine. As long as you are operating at or below 75% power leaning may be possible at any altitude. (Be sure to verify this with your POH.)

Most of today's small airplanes will fly on 100LL, even if they were certified to operate on 80/87. The color of the fuel will be the indicator of the grade of the fuel. We all know that 100LL is pale blue and 80/87 is pale red. Mixing these two grades will make the color of either one fade away. The fuel will appear to be colorless. The same should occur if automotive fuel is mixed with an aviation grade of fuel. Turbine fuel by itself is clear or slightly yellow and is oily to the touch. Using turbine fuel in a piston is detrimental. It burns at a higher temperature and will, in a very short time, burn your exhaust valves up leaving you with an engine that will not produce any power.

With a bit of planning and knowledge of your airplane's fuel system your flying experience should be free from an untimely utterance of "Oh #@%*,…I can't be out of gas?!"

Upcoming Events

July 18th
Sponsored by the St Louis Chapter
Missouri Pilots Association
Thunder Aviation's New Terminal
(next to Wings of Hope)
Spirit of St. Louis Airport
Runway Safety Action Team (RSAT)
7 to 9PM.

Good maintenance is no accident
Steven Long
Airworthiness Safety Program Manager
1-800-322-8876 extension 4830
Steven.Long@faa.gov