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.