“Almost half of pilots involved in fuel management accidents hold either a Commercial or Air Transport Pilot certificate.”
From an Australian Transport Safety Bureau (ATSB) report:
The pilot of a Beech Baron 58 aircraft contacted a refueler and requested 400 liters (about 105 U.S. gallons) of fuel be added to the aircraft. The refueller provided 200 liters of fuel, however the refueller recorded the amount provided as 400 liters.
At the end of the day, the refueller totaled the daily fuel delivery quantities and detected a 200
-liter discrepancy between the recorded deliveries and the fuel tank meter readings. The refueller identified that the discrepancy was due to an error in the refueling of the Baron in question. He immediately went to the aircraft to notify the pilot of the error. However, he was not able to locate the pilot. The refueler was then distracted by a phone call and forgot about the refueling error.
Eleven days later, another pilot prepared to conduct a ferry flight in the aircraft. The takeoff and climb were uneventful. About 5 nm north of the planned destination, both engines failed. The pilot conducted a forced landing i n a paddock (pasture). During the landing roll the aircraft impacted a number of bushes. The pilot was not injured, however, the aircraft sustained substantial damage.
This incident underlines the importance of communication once an error has been discovered. The refueling error was discovered 11 days prior to the incident flight, however, this was not communicated to the Baron’s operator or its pilots. Knowledge of the error would have enabled the pilots to correct the fuel log and avoid the incident.
And from the National Transportation Safety Board:
The pilot of a Piper Seneca departed in night instrument meteorological conditions with the airplane’s fuel tanks full, providing an estimated fuel endurance of four hours 50 minutes. Two hours 50 minutes into the flight, the pilot reported a loss of engine power on the right engine, followed by a loss of engine power on the left engine. The pilot attempted to land at a nearby airport; however, the airplane impacted trees about 8 miles short of the airport. A review of weather information revealed no evidence of in-flight icing or other weather conditions that may have contributed to the accident.
The left engine fuel selector valve was found in the “X-FEED” (crossfeed) position. The right engine fuel selector was in the “ON” position. With the valves in these positions, both the left and right engines would have consumed fuel from the right fuel tank. Review of performance charts and fueling records indicated that if the flight was conducted with the valves in the as-found positions, exhaustion of the fuel in the airplane’s right fuel tank would have occurred about the time the pilot reported the dual engine failure. In addition, the yaw trim was found in the full nose-right position. It is possible that the pilot used nose-right yaw trim to counteract an increasing left-turning tendency during the flight as fuel was burned from only the right wing’s fuel tank making it relatively lighter than the left wing.
According to the checklist in the Seneca Pilot’s Operating Handbook, during taxi the pilot was to move each fuel selector to “X-FEED” for a short time, while the other selector was in the “ON” position, before returning both fuel selectors to the “ON” position before takeoff. According to a checklist found in the airplane, the fuel selectors were to be set to “X-FEED” during taxi and then to “ON” during engine run-up. GPS data recovered from onboard devices indicated that the pilot taxied from the ramp and onto the active runway without stopping in about three minutes, indicating that it is unlikely he performed a complete run-up of both engines before takeoff. He likely failed to return the left engine fuel selector from the “X-FEED” to the “ON” position, where it remained throughout the flight and resulted in fuel starvation and a loss of engine power on both engines.
Focus on Fuel
The NTSB continues to identify fuel mismanagement as a common factor in airplane accidents. Lest pilots of twin and turbine airplanes feel complacent, in its recent Safety Alert 67: Flying on Empty (August 2017), the NTSB notes:
- Almost half of pilots involved in fuel management accidents hold either a Commercial or Air Transport Pilot certificate (48 percent);
- Pilots holding Private or Sport Pilot certificates make up 50 percent of those who have had fuel mismanagement events;
- Only 2 percent of fuel-related mishaps involved student pilots.
Fuel exhaustion (running completely out of fuel) and fuel starvation (having fuel onboard that doesn’t reach the engine because of improperly set selectors, a blockage or water contamination) were implicated in an average of more than 50 accidents per year since 2010, according the NTSB. Fuel exhaustion accounted for a little more than half (56 percent), while fuel starvation resulted in 35 percent of the crashes.
“An overwhelming majority of investigations of fuel management accidents – 95 percent – cited personnel issues (such as use of equipment, planning, or experience in the type of aircraft being flown) as causal or contributing to fuel exhaustion or starvation accidents, Prudent pilot action can eliminate these issues. Less than 5 percent of investigations cited a failure or malfunction of the fuel system.”
Most multi-engine airplanes are low-wing types with a fair amount of dihedral. Because of the dihedral “slope” of the wing, fuel filler ports are at the outboard, high-end of fuel tanks. Consequently, in many airplane types there may be no fuel visible at all through the filler ports when there is still significant fuel remaining in the tank. In other words, determining the amount of fuel on board must include ways to accurately detect and track less-than-full fuel levels that are independent of visual inspection.
Fuel awareness requires you use several independent means to judge fuel state. Pilots make totalizer data entry errors. Ground handlers make fueling errors or sometimes forget to add fuel altogether. Fuel burn may vary from flight to flight. And aircraft fuel gauges are sometimes inaccurate. Where fuel is concerned, you need to be uncompromising and skeptical.
There are many independent ways to check and track fuel state:
- A visual check of fuel level in the tanks;
- The indications on cockpit fuel gauges;
- Wing-mounted fuel sight gauges, when installed;
- The “fuel remaining” amount on a fuel totalizer;
- The amount of fuel you personally put into the tanks, or watch being added prior to the flight;
- Fuel records, compared to the engine tach time or airplane Hobbs time when the fuel was last added.
Fuel totalizers are among the best safety devices on an aircraft. But their information is only as good as the accuracy of the pilot’s inputs. If you’ve ever delayed or forgotten to input fuel load, or have entered “approximate” data, all those little errors can eventually add up. It’s best to routinely top the tanks and reset the totalizer at “full” to avoid creeping inaccuracies in the fuel-remaining data.
Not all methods work for all airplane types or all fuel levels. The trick is to look for discrepancies between one or more available method and the others. If any one indication differs noticeably from the others, the only means to resolve the discrepancy is to add fuel until it is at a level known to be sufficient to complete the flight with reserves. This fuel status technique is especially helpful if the flight requires a less-than-full fuel load for weight and balance purposes or for improved performance.
This is even more critical when more than one pilot flies the airplane. For several years I flew and managed two Beech Barons for a company in Tennessee. I generally flew one, and the company CEO flew the other. At times, however, we would swap, sometimes with little notice. We adopted a policy to check the fuel level using every possible way from the list above. If any one indication differed noticeably from the others, we would suspect them all, and add enough fuel to either:
- be able to visually confirm the fuel level in the tanks, or;
- complete the planned flight with the fuel we put in the airplane at that time (most of our trips were short, about an hour plus reserves).
With that operating philosophy, we never departed with concern about the amount of fuel on board.
Once airborne, monitor fuel state and crosscheck expectations against actual fuel burn as you progress along your route. Different power and mixture settings, or slower-than-planned ground speed, will affect your fuel reserves. Don’t forget to occasionally check fuel caps and the trailing edge of the wing behind fuel caps and vents for any signs of fuel venting overboard in flight. I added a step to my “climb checklist” to remind me to check behind fuel caps and along the trialing edge of the wing for any sign of fuel leaks. If fuel is venting, land at the nearest airport, correct the source of the fuel leak if possible (secure the caps), and add fuel until you can confirm you have enough to make it to destination with reserves.
Don’t dismiss a fuel gauge showing a fuel level lower than you’d expect. It may be telling the truth. Conversely, some inflight venting scenarios will cause cockpit gauges to read fuller than actual. You might have to land early to double-check the fuel load if a discrepancy arises between indicated fuel level and your flight planning expectations.
Fuel status tracking is even more important if you’re flying an airplane with multiple, independently selectable fuel tanks. Some twins, especially older ones, have a fuel return that may or may not go to the tank in use. This can create a situation where fuel may be wasted overboard through the vents if the return-fuel tank is over-filled. If you need to move the fuel selector, you need to actively monitor fuel state for each tank individually.
How could the Baron and Seneca pilots – and the many more each year – avoid fuel mismanagement accidents?
- Personally watch the airplane when it is fueled;
- Crosscheck fuel level by all means that are possible;
- Follow before takeoff and inflight checklists meticulously;
- Predict “fuel used” and “fuel remaining” levels at waypoints along your route of flight, and crosscheck to see that you are meeting or exceeding estimates for fuel remaining as you pass each;
- If you have individually selectable fuel tanks for each engine, before takeoff make a written plan of when and where you will change tank selection, and follow that plan in flight;
- Don’t rely on a single method of deciding there’s enough fuel on board to begin or complete a trip;
- Divert early, divert often if you have any doubt about your ability to arrive with a healthy fuel reserve.
Aircraft crashes are especially tragic when they are the result of pilot-induced engine failure. Manage and monitor to avoid fuel trouble.•T&T