Cessna TU206G N235HM accident near Saint Ignatius, Montana

Probable cause

Maintenance personnel’s failure to tighten a fuel line, which resulted in a loss of fuel pressure and a subsequent loss of engine power during cruise flight and an off-airport landing and collision with obstacles.

NTSB analysis

The pilot was conducting the airplane's first flight since the engine had undergone maintenance several months earlier. He reported that, after about 45 minutes of flight, he noticed that the exhaust gas temperature (EGT) had increased but that he was able to reduce the temperature by increasing the fuel flow. Shortly after, the EGT again increased, and the pilot began to troubleshoot the issue. The pilot stated that, after he turned the electric fuel boost pump on a second time, the engine ran normally for about 2 minutes and then lost power. He determined that the airplane would be unable to reach the airport, so he initiated a forced landing to a road. During the landing roll, the airplane struck vegetation and a fence.

During a postaccident examination of the airplane, blue fuel stains were observed on the top of the engine. The fuel line attached to the fuel flow transducer was found finger tight and leaking. A review of the airplane's maintenance records indicated that, during the maintenance conducted several months before the accident, three cylinders, including the No. 6 cylinder, had been removed and reinstalled. The fuel line attached to the fuel flow transducer was just above the No. 6 cylinder and, therefore, it would been removed to access the cylinder during the maintenance. It is likely that maintenance personnel did not adequately tighten the fuel line during its reinstallation, which led to the loss of fuel pressure and the subsequent loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR15LA229 for the full record.