Piper PA-30 N4009Y accident near St Ignatius, Montana

Probable cause

A partial loss of power during takeoff for undetermined reasons.

NTSB analysis

The pilot was repositioning the airplane to a local airport for maintenance and an annual inspection. The pilot stated the engine start and runup were normal. During takeoff, shortly after the airplane exited ground effect, the left engine had a partial loss of power. The pilot saw powerlines and, to avoid them, initiated a forced landing on a road just past the end of the runway.

Postaccident examination of the airframe and engine did not reveal any mechanical anomalies that existed before the impact.

The pilot reported that the airplane sat idle for several years and he last added fuel to the airplane about 2 years before the accident. A fuel sample from the accident airplane was green in color, consistent with the introduction of copper to aviation grade gasoline, which typically presents after the fuel has been stagnant for over 2 years. Although it’s possible that the condition of the fuel affected its combustion properties, further testing of the accident fuel for combustion could not be completed due to the disposal of the recovered fuel.

Text from the NTSB. Open the NTSB docket for WPR22LA313 for the full record.