The commercial pilot reported that, during a post-maintenance test flight, the Piper PA31’s right engine surged and then behaved consistent with a fuel flow issue. The right engine subsequently lost power, and the pilot prepared to return to the airport.
However, before he could secure the right engine, the left engine started to surge and then lost power.
The pilot conducted a forced landing to a field near Denton, Texas, during which both wings and the engine nacelles sustained substantial damage.
Although a fuel smell was present on scene, there was no visual evidence of fuel in the fuel tanks or in the field.
Only a quart of fuel was recovered from the left fuel tank.
Further examination of the airframe and fuel system revealed that the fuel tanks were not compromised, and no mechanical anomalies with the airframe, engine, or the fuel system were found that would have precluded normal operation.
The pilot reported that there should have been about 120 gallons of fuel on board at the time of departure. Additionally, a fuel receipt confirmed that 99.36 gallons of fuel had been added to the fuel tanks before a 36-minute maintenance engine test run conducted three days before the accident.
No other flights were conducted between the test run and the accident flight, which the engine data monitor indicated was about 30 minutes long.
Based upon calibrations set by the operator, the engine data showed that the engines consumed about 5.6 gallons of fuel during the test run and 19.2 gallons of fuel during the accident flight.
Performance information from the manufacturer indicated that the engines should have burned between 10 and 18 gallons of fuel during the test run and between 27 and 50 gallons of fuel during the accident flight.
Although it is possible the discrepancy between the recorded fuel consumption and the fuel consumption calculations was due to the operator setting the engine data monitor’s calibrations incorrectly, it could not be determined when or by whom the calibrations were set.
The absence of fuel on-scene and the loss of engine power are consistent with fuel exhaustion, however the investigation was unable to determine why there was no fuel on board at the time of the accident.
Probable cause: The total loss of engine power due to fuel exhaustion for reasons that could not be determined.
NTSB Identification: CEN16LA102
This January 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
In his statement to the NTSB the pilot said that during his pre-flight on the day of the accident “As is my custom, I visually checked the mains fuel level (full) and seated the filler caps myself. There was also some fuel in the outboards.” That there was no fuel in the aircraft after just a short flight suggests he may have THOUGHT he checked the fuel, but because of some distraction his expectation bias (defined as “where previous patterns and information held in memory influence what we currently perceive”) created false memories of observation.
Here’s an interesting factoid that is perhaps unrelated to the lack of fuel, but may be indicative of another area of complacency:
Both the pilot/operator report (NTSB Form 6021and the pilot’s statements in the NTSB Docket which supports the NTSB Final said the pilot seat in the aircraft was equipped with just a lap belt. As a result, the pilot experienced some nasty cuts to his head and face because he hinged violently at the waste and his face struck the panel. It seems like the owner of the aircraft (and the pilot who was working with him) overlooked the cheapest and most effective safety accessory we can install in an aircraft: 4 point harnesses. The pilot is lucky that he survived his controlled crash. A lot of pilots (and front seat passengers) have died because they impaled their skulls on pointy parts of the pane,l or despite having survivable injuries, were knocked unconscious and died in a post crash fire.
Only a preflight visual check of the fuel tanks prior to engine start matters and that would appear to not have been done unless I missed something in the report. Correlation between the visual check and the fuel gauge indication is the only reliable preflight check. Otherwise it’s a crap shoot. FEs on the DC-8 for example (revealing my age and experience) always “stuck/sticked” the wing tanks during preflight to confirm fuel on board and accuracy of fuel indications before engine start. No they didn’t climb on top of the wing and stuck a probe into the tanks. The tanks had a calibrated device referred to as a “stick” that could be released from beneath the tanks while standing on the ground using a pole device to reach it which when released would hang down out of the wing indicating the amount of fuel in the tank. The same in principle applies to GA airplanes. Engines won’t run without fuel. Gee, what a profound concept!
“there should have been about 120 gallons of fuel on board”. And what did the fuel gauges in the cockpit and externally on the wing indicate?
Maybe the fuel was stolen….. It happens which is why you ALWAYS check fuel levels during preflight. If a cap was loose it could also allow fuel to be siphoned out… But in this case both caps would have had to be loose.
Reading the full NTSB report, one gets the idea that this aircraft was in a hangar, group or single, doesn’t say (and having been based in the area, you really want to have your aircraft in a hangar).
So, there was a puddle of fuel on the floor under one of the tanks. But it appeared to be a very small amount (IIRC, about a cup of fuel).
The pilot did a full preflight, with the exception of visually inspecting the tanks. The inspectors looking at this apparently understood that the aircraft was secured between the maintenance flights.
My thinking is, the FBO has a fuel thief — I’m thinking this was an inside job (no pun intended).
Agree with your speculation. It’s inconvenient and sometimes a PITA, but even fuel quantities in high wing GA aircraft are best visually checked each pre-flight. I know several pilots who don’t do that. I guess they are “experiential learners” awaiting arrival of that ‘teachable moment’ on some future (hopefully solo) flight. 🙂
Just read the pilot’s report which is in the docket. In it he said the aircraft was fully fueled three days prior, that he did a long runup on that date (30 minutes) then returned the aircraft to the hangar because he wasn’t yet on the insurance policy. He said he pre-flighted the airplane before the accident flight, and ‘visually checked’ the fuel. What’s not clear is whether he correctly recalled he visually checked the fuel prior to the accident flight or if the visual check was prior to refueling it. The docket does not contain any statement by Gary, the A&P who worked on the aircraft, though there is a suggestion that he may have in some way participated in the final pre-flight before going off to work on another similar aircraft.
I agree with you Wylber. Someone either stole fuel out of the tanks or the fueler sold him more fuel than he actually put in the tanks. Of course, that doesn’t excuse the fact that he didn’t visually check the fuel quantity.