Top Four Fuel Exhaustion Excuses

Many pilots think running out of fuel is in the same category of a gear-up landing: It can never happen to them, until it does. While there may be several good reasons for landing with the gear still stowed, we can think of only two for running out of fuel. One of them involves fuel starvation-theres fuel aboard, but it cant get to the engine. In our view, the only time this excuse holds water is when it involves some kind of mechanical event-the fuel selector breaks off in the pilots hand between

detents, for example, or a transfer pump fails. The only other legitimate excuse for running out of gas is when the weather caves and theres literally no place to land within our dwindling range. And thats rare enough we couldnt find any recent examples, although they may be out there.

We looked at five years of NTSB fuel-related accident records-totaling an eye-popping 429 events-to narrow down four principal reasons pilots run out of gas, or what we define as fuel exhaustion. Notably, the most-prevalent reason-by far-in the NTSB data involves pilots who fail to take off with enough fuel for the planned flight.

Our poster-child example of such behavior took off in a V-tail Bonanza on August 5, 2009. The pilot was headed for an airport 17 miles away for-would you believe it?-fuel. He climbed to approximately 3000 feet and was roughly halfway-eight miles, according to the NTSB-when “the airplanes single engine stopped producing power.” He switched tanks and activated the electric fuel pump, which restored power. Briefly. He made it another five miles until the engine again lost power, forcing him to land in a field. During the roll-out, the Bonanza nosed over and came to rest inverted. The FAA inspector who came out could find no evidence of fuel leaking after the airplane came to rest, but verified the tanks were both intact and contained only residual amounts of the precious liquid.

To really understand how little fuel was aboard this Bonanza, lets do the math. First, well presume it was a relatively recent model, easily capable of cruising at 160 knots or so, but on this short flight really only averaged, say, 120 once the wheels left the ground. Well also give the benefit of the doubt and suggest it had a large displacement engine, which can go through fuel, and guesstimate the airplanes fuel burn for takeoff, initial climb and full-rich, low-altitude cruise at 30 gph. Well also throw in three gallons for engine start, taxi and run-up, plus the inevitable delay for the slowpokes in the pattern.

To cover 17 nm at 120 knots requires 8.5 minutes. At our generous 30 gph fuel burn, that requires 3.52 gallons of gas. Add the three gallons for ground time, and this pilot left the ground with less than 6.52 gallons of usable fuel aboard. Not bad if youre flying an LSA burning four gallons an hour, but pretty sad in a high-performance single.

In this day and age of high-priced aviation fuel, we get the idea of seeking out the least-expensive gas we can find. Been there, done that. But in this accident, the pilot either didnt check to see how much fuel was aboard, or didnt care.

From Day One of our primary training, were taught to verify the fuel amount aboard by visually inspecting the tanks. Some tanks-like the Bonanzas-make it difficult to see the fuel level without either a flashlight and/or a dipstick. Even then, it may well have been impossible to see fuel in this Bonanzas tank. Thats when-as we all were trained, hopefully-one adds fuel until it can be seen. At least well know how much we added. If theres no fuel available, we wait for the FBO to open, or scrounge some cans and hitch a ride to a nearby airport. This isnt rocket science.

Unforecast weather-or a general failure to consider weathers implications on fuel requirements-is another excuse. The classic weather-related excuse for running out of gas is headwinds, and we didnt have to look hard to find a good example.

On April 12, 2007, a pilot departed El Monte, Calif., in a Cessna 172M with both fuel tanks full of 100LL. The airplane had been modified by installing a 180-hp Lycoming O-360 engine in place of the original 160-hp O-320. According to the NTSB, his planned flight to Stockton, Calif., usually requires three hours. On this flight, however, turbulence and strong winds extended it to four hours. As he lined up for a straight-in approach to Stockton, the engine stopped due to fuel exhaustion. The pilot executed a forced landing short of the runway, collapsing the nose gear and buckling the engine firewall. An FAA inspector at the accident scene confirmed there was no fuel aboard.

From experience, we know a 180-hp Skyhawk burns more gas than the standard 160-hp version. There are charts demonstrating this, which should be with the airplanes paperwork in the cockpit. Further, it seems the pilot flew the route in this airplane often enough to know how long it takes.

We also know its a hassle to land and refuel, especially in windy conditions. But this pilot had ample opportunity to refuel, advise his destination of the delay and continue. As proof, we used a popular online service to find airports along this route with instrument approaches, at least a 3000-foot runway and within 20 nm of the direct route from El Monte to Stockton. We counted 27 such opportunities.

As we all should know, a manufacturers fuel consumption tables are based on best-case scenarios, which often are driven by marketing considerations and are not valid in the real world. Some skepticism is in order, at least until experience with the airplane is gained. As proof, we offer up the tale of a pilot with 16 hours in a rented Piper PA-32-260.

The pilot flight-planned a 14-gph fuel burn for the three-hour flight. With five people and camping gear aboard, the pilot was able to fill both main fuel tanks, and partially fill the left tip tank for a total of 60 gallons of fuel. After takeoff, the pilot climbed to 5500 feet, set power and leaned the mixture. Soon, however, the pilot noted high engine temperatures and enrichened the mixture a bit.

After exhausting the left tip tank, he switched between the left and right mains every 30 minutes for most of the remainder of the flight. About 30 minutes prior to reaching the destination, the pilot observed approximately 14 gallons of fuel remaining, which he equated to an hour of flight time.

Soon, the left tank was emptied and he switched to the right one, but about two miles from the destination, “fuel was exhausted and the engine quit.” During the forced landing, the airplane clipped a perimeter fence, landed on a road and rolled into a ditch.

Although this is another instance where landing and refueling would have made the difference, enrichening the mixture should have been a warning that fuel consumption was going to be higher than planned. By the time we factor in taxi, takeoff and climb fuel, plus the anticipated 14-gph fuel burn, taking off with 60 gallons for a three-hour flight doesnt leave much room for error if we want to land with legal reserves. Improperly leaning the mixture can drastically increase the fuel required, especially during a multi-hour cross-country flight.

Our final fuel exhaustion excuse involves quantity instrumentation. Aircraft certification rules only require fuel gauges to be accurate when theyre reading empty. Despite the wisdom of that standard, trusting fuel quantity gauges is a time-honored way to run out of gas.

This example involves a piston-twin pilot who later said he started the accident flight with 500 pounds of fuel, which he thought was sufficient. Approximately 12 miles from the destination airport, both engines lost power. The pilot was vectored to a 2700-foot-long turf strip he spotted through breaks in clouds, landing on wet grass. The airplane overran the runway and impacted trees.

The pilot said he used the fuel gauges to determine quantity and the right indicator “consistently reads two hundred pounds less than the left” one. In its probable cause finding, the NTSB noted “the pilots reliance on inaccurate fuel gauges” was a contributing factor.

Running out of fuel is something we all must consider on every flight. But its one of the most preventable accident causes there is. According to the AOPA Air Safety Foundations 2008 Nall Report, “lack of fuel on board is nonnegotiable.” While the trends for this kind of accident are encouraging-in part thanks to fuel totalizers-ensuring there is adequate fuel on board is Airmanship 101.