Continuing Ed

It Doesn't Take A Genius

The report on the local television news contained sketchy details, as is often the case with an accident involving a light general aviation airplane. The Piper Cherokee reportedly crashed into trees short of the runway on final approach. Fortunately, the pilot and a passenger were not seriously injured.

What could have happened? A catastrophic engine failure is a possibility, but that is an extremely rare event - especially on final approach when the engine is at a very low power setting.

Carburetor icing? Perhaps, but in the local climate at this time of year, not very likely.

The only other detail provided in the story proved to be telling. The accident occurred at the pilot's home airport at the conclusion of a cross-country flight of about 475 nautical miles. Hmmm...

I don't know the model Cherokee involved, so I can't be certain about the fuel capacity. Some models have 36 gallons of useable fuel, some 48, and some 50. But in checking the manufacturer's stated range for each model, it's clear that a flight of that length would be at the outer limits of almost any Cherokee model. Throw in less-than-ideal wind conditions, or tanks that weren't quite full on departure, and you could easily come up short of fuel to reach your destination.

In fact, that may be why this accident occurred. The airplane crashed short of the airport because the tanks were empty of fuel after such a long nonstop flight. If that's indeed the case, there's no excuse. During the last quarter of the trip alone, the pilot passed very close to at least eight airports that have fuel available.

If the crash resulted from fuel starvation, the pilot may have made a crucial error while planning the trip. For example, he may have departed with less fuel in the tanks than he thought. How? If the airplane had sat in the hot sun for several hours with the tanks full, the fuel could have expanded and overflowed through the tank vent line.

It's also possible that the tanks had not been completely topped off and the pilot failed to physically check the quantity before departing. He may have improperly leaned the mixture, resulting in an overly rich mixture and excessive fuel consumption. Or he may have planned the trip on the basis of range without accounting for fuel used in taxiing, runup, takeoff, the climb to cruise altitude, or headwinds.

The other possibility is that the planning was good, but the pilot's judgment was incredibly poor. How else to explain why someone would willfully choose to take a chance on stretching a flight to the limits of fuel endurance - and perhaps even beyond - in the belief that he could somehow beat the odds and make it home without running dry? Some pilots do indeed take that chance. According to the AOPA Air Safety Foundation's Nall Report, in 1997 there were 110 accidents caused by fuel exhaustion.

What were these pilots thinking as they pressed on through the day or night, surely aware on some level that they were risking the lives of everyone on board? Did they want to avoid paying a higher price for fuel at an en-route FBO than they could get at home base? Were they rushed for time, feeling that they couldn't afford to take the extra 45 minutes or hour that an en-route fuel stop typically adds to total trip time? Did they not want to admit to themselves or to their passengers that they had planned the trip poorly by failing to put enough fuel on board to make the trip and land with safe reserves? Whatever the reason, in hindsight it must look like what it is: stupid and irresponsible.

Smart, safe fuel management involves more than simply filling the tanks and watching the gauges, but not a whole lot more. Here are five points to keep in mind and help to ensure that you won't have to sweat making your destination with adequate fuel.

1. Know precisely how much fuel is in the tanks prior to departure. You can't know how much fuel you've used and how much remains unless you know exactly how much you started with.
2. Know the fuel consumption characteristics of your airplane under a variety of flight conditions: altitude, ambient temperature, aircraft weight, and power and mixture settings. Each of these factors affects fuel consumption. The more you know about the thirst patterns of your airplane, the better you can manage its fuel consumption.
3. Lean properly to get the best mileage from every drop of fuel that you burn. An overly rich mixture increases fuel consumption and robs your engine of performance.
4. Use the clock - not the fuel quantity indicators on the panel - as your fuel gauge. In other words, plan and track your fuel consumption based on endurance, not range. Unlike range, endurance is not at the mercy of winds. Besides, those fuel gauge indicators probably won't be very accurate except when they read empty - a setting you should never see. If you know how much fuel your engine uses at the specific altitude and power setting you're flying, you can easily calculate fuel consumption, fuel used, fuel remaining, and how much fuel you should have in the tanks when you land.
5. Pad your fuel consumption calculations to give yourself a safety margin. For example, if the airplane burns eight gallons per hour, use 8.5 gph for planning purposes. The margin allows for increased fuel consumption caused by unanticipated climbing or a lower-altitude cruise. And don't forget to add in fuel consumed during taxiing, runup, climbing, and descending.

An accident that results from fuel starvation - running the tanks dry - is, in one respect, the worst kind of accident because it is the most preventable kind of accident. There is no excuse for running out of fuel, only an explanation: stupidity.