Accident Report: The fuel remaining

Precautionary landings are defined in the FAA’s Airplane Flying Handbook as “a premeditated landing, on or off an airport, when further flight is possible but inadvisable. Examples of conditions that may call for a precautionary landing include deteriorating weather, being lost, fuel shortage, and gradually developing engine trouble.”

Given that definition, the off-airport variety, although less risky than a Hollywood-style forced landing, is the preferred option for safety in a situation where the safety chain is about to break. Often when it does break, it’s because a pilot senses, rightly or wrongly, that fuel is in short supply.

The fuel shortages that lead to emergency landings come in several varieties. There’s the fuel-exhaustion scenario that takes a pilot by surprise, requiring an immediate (forced) landing on whatever surface lies beneath. Fuel starvation is a variation on this theme. A pilot may think fuel is exhausted—only to find out later that sufficient fuel was available in another tank that was not selected for use when the engine stopped.

Another kind of fuel shortage is perceived when a flight seems likely to exceed its assumed time aloft—a scenario sometimes compounded by the pilot’s lack of familiarity with the aircraft’s demonstrated fuel consumption. On June 22, 2020, a 272-hour private pilot flying a recently purchased Cessna 150 experienced a hard landing when setting down the aircraft (with its engine sputtering) in a field in Shelby, North Carolina. The accident site was about three miles short of the destination airport.

According to the NTSB accident report, the pilot reported departing with full tanks, and noted that while receiving radar flight following en route, he complied with an air traffic control request to “adjust his heading” before being “routed back on course.”

“After the airplane was recovered, the pilot drained the unbreached fuel tanks and 3 gallons were removed from the airplane. According to the airplane’s pilot operating handbook, the airplane held 26 total gallons of fuel, of which 22.5 gallons were useable,” the report said.

The pilot had been watching the fuel gauges during the flight, and his statements were offered in terms of gauge indications, not calculated fuel remaining. The accident might have been avoided, “if I had stopped and fueled when I was at one-quarter tank of useable fuel,” he noted on the NTSB’s accident reporting form. “I had only had [the] plane for 10 days and had flown it for 11 hours,” he said.

The NTSB determined the probable accident cause as “the pilot’s inadequate preflight and inflight fuel planning, which resulted in fuel exhaustion.”

Always plan to be on the ground long before the time aloft offered by your fuel supply.If fuel exhaustion occurs all too regularly year after year, consider how demoralizing it might be to make a precautionary landing (substantial damage resulting) based on a guesstimate of fuel remaining, only to learn that an hour of usable fuel remained.This unfortunate outcome was experienced by a 3,600-hour private pilot flying a big-engine Bellanca Viking on June 19, 2020, near Martinton, Illinois.

According to the NTSB, the pilot, who had a passenger aboard, began to suspect imminent fuel exhaustion at a 19-gallon-per-hour fuel burn after flying about three hours of a cross-country. Seeing no runway nearby, he went for a gravel road.

“During the landing the airplane exited the road and went into a ditch, substantially damaging the fuselage. Post-accident examination of the airplane revealed that it contained about one hour of useable fuel,” the accident report said, affixing the probable cause as “the pilot’s improper decision to conduct an off-field precautionary landing.”

If these two accidents bracket the ways a pilot can fall short on estimating fuel remaining, their other common element is that the precautionary landings on terrain more or less of their own choosing were survivable. These accidents also illustrate the simple steps you can take to avoid similar predicaments and the likely criticism that you acted either too late or too soon.

Build a true knowledge of your engine’s fuel-consumption before planning a flight close to the published limits. Another is to always plan to be on the ground—that is, a runway—long before the time aloft offered by your fuel supply, despite any inconvenience that might cause.

Until your familiarity with the aircraft you fly rises to a high level of confidence, plan your flights based on a higher-then-expected fuel burn and a lower quantity of fuel than you actually carry. Then for good measure, set aside more than the fuel reserves required by regulations as a further boost to your safety margin. No one waiting at the destination will mind if you show up a little late.

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