Acknowledgements: Thomas P. Turner, Mastery Flight Training, Inc. & Flight Instructor Hall of Fame inductee
A twin-engine airplane’s pilot told reporters he was less than two miles from his destination airport when both engines quit. Attempting to land on a highway, he instead ended up a ditch, escaping unhurt despite “totalling” the airplane.
It seems like every time I read about fuel exhaustion - someone running completely out of fuel - it strikes me how frequently the pilot almost makes it to destination. It’s amazing how often an airplane runs out of gas within a mile or two of the planned destination airport!
As a data enthusiast, I planned a detailed romp through the National Transportation Safety Board (NTSB) database to see if there is any truth to my growing assumption that fuel-exhaustion is often a “just a little bit more to get home” phenomenon, and if so, if there’s some way to use this knowledge to prevent similar future events .... I’ve not had time to complete my survey, but I have made a brief, initial stab at it, and if the data are consistent over longer time-frames then my assumption may be proved correct.
I began looking by a search of all “fuel-exhaustion” events in the NTSB database in the past 10 years. I quickly saw I didn’t have time to review the entire batch before this week’s edition; in the interest of time I eventually looked only at fuel-exhaustion events for a single calendar year for which final (“Probable Cause”) reports are posted. I’m sometimes cynical about aircraft accidents (given that I spend so much time looking at and thinking about them). But frankly even I was surprised at how many fuel-exhaustion reports I found: 56 reports, slightly more than one on average every week.
I read each report and noted how many occurred in or near the pattern for the planned destination airport. Removing four that involved airplanes remaining in the airport traffic pattern for the entire flight, and three more involving aerial application flights working away from a dedicated airport, I learned that 27 of the 49 reports occurred while the airplane was in the traffic pattern at the end of a cross-country flight. In many of those cases the airplane was on final approach when the engine (or engines) quit! In three additional cases the aircraft was within a few miles of destination and descending when the fuel ran out.
Remember that these are all fuel-exhaustion reports, when investigation determined there was essentially no fuel remaining anywhere on board the aircraft when it crashed. So, issues of switching fuel tanks near the ground, or violating limitations against descent and landing on auxiliary fuel tanks, or fuel un-porting in a steep slip are all outside the scope of that brief look at one year’s record. These events were all simply attempting to fly farther than the fuelled range of the aircraft.
In many of the reports, the pilot (if he/she survived) reports having made what appears to have been thoughtful pre-flight fuel decisions. But they are also often based on rules of thumb (“my airplane always burns XX gallons per hour” or “it usually takes XX hours and minutes to make this trip”) for considerations that are frequently variable based on power setting, altitude, mixture management technique and winds.
In many more, the pilot clearly knew he/she was running low on fuel before the gas ran out, often reporting the same to Air Traffic Control or after the fact to investigators. In other words, the pilot was aware enough of the fuel state to know trouble was near but didn’t do anything about it soon enough to make a difference.
Nearly half of all reported fuel-exhaustions did not happen in the traffic pattern of the home airport. Those events almost universally occur somewhere during the en-route phase of a cross-country trip, or after a missed approach and while en-route to an airport half an hour or more away.
(But in over half of cases) It (therefore) stands out in the data that pilots are pushing fuel to the last minutes before landing, on the flight home.
Why might a pilot be more likely to run out of gas at the end of a trip home? Three things spring immediately to mind:
First, most pilots get a “based-aircraft” fuel discount at their home airport. There’s an inherent conflict between the need to fuel up for a flight home and the fact that getting home with the least amount of fuel on board includes a financial reward.
Second, I think pilots may be less likely to decide to divert for fuel on the way home. Pilots generally love to travel, but we all like to get home. The desire to complete a trip, perhaps coupled with incentives or stresses to be back at the office or in the home, may make us less likely to stop short just as we’re within 30 to 45 minutes (our legal reserves) of destination.
Third, fuelling away from home can sometimes be a hassle. We might not want to take the time or make the effort to fuel up if we think we can make it home with what we’ve got. Under external or self-imposed pressure to get home, we’re less tolerant of delay, and can more easily rationalize going unrefuelled if for any reason we are unable (or unwilling) to get gas at the remote location.
There are many potential FLYING LESSONS in this realization, including:
We can plan expected fuel burn, but we need to actively monitor fuel burn in flight, using as many independent means as possible to account for changes in power setting, mixture technique, and real-world winds aloft.
We need to consider the added fuel burn of take-off and climb when planning a near-maximum-range flight. Rules of thumb about cruise fuel burn rates won’t cut it when we’re cutting it short.
We must consider our planned reserve an inviolate emergency resource. In other words, if an in-flight check of fuel state shows you’ll begin burning into your 30-minute/45-minute/or more conservative personal fuel reserves, you must remain in a position to land for gas before you access the first portion of your reserve fuel. Fuel reserves are for emergencies, not for convenience.