What happened
During a maintenance test flight intended to verify a newly overhauled engine, the pilot of a Piper PA-24-260 Comanche began experiencing a gradual loss of engine power. This occurred at approximately 300 feet of altitude during the initial takeoff climb. The pilot attempted to return to the airport by executing a left turn; however, insufficient altitude resulted in an impact with swampy terrain located on the west side of a lagoon.
During the maneuver to return to the airport, the pilot switched the fuel selector from the left tank to the right tank and back to the left tank, but this action provided no correction for the power loss. The pilot noted that the fuel flow indicator dropped from 28 to 17 gallons per hour. Prior to takeoff, the pilot had performed two ground run-up checks at approximately 2,200 RPM and observed no discrepancies.
The investigation
Following the recovery of the N-number not provided aircraft, an engine examination was conducted by the pilot/mechanic and a representative from New Piper Aircraft, Inc., under FAA oversight. During a fuel flow test with the electrical fuel pump energized, investigators observed fuel spraying from the fuel line at the fuel servo that supplies the flow divider. This was attributed to a loose B-nut. The test was temporarily halted to tighten the nut before resuming.
Further testing of the fuel mixture flow showed a rich mixture flow of approximately 7 gallons per hour and a lean mixture flow of approximately 4 gallons per hour. Maintenance logs indicated that the engine installation followed the Lycoming Overhaul Manual. While service instructions recommend ground run-up checks at full-static power for no more than 10 seconds, the aircraft flight manual specifies full-static power as 2,700 RPM with the turbocharger control off.