Clayton

The pilot was departing the private, fly-in community airport on a personal flight. He was familiar with the airport/fly-in community and was instrumental in its development. Fog was present at the time, and, according to witnesses, it was "rolling up the valley," which was a frequent event at the airport. The witnesses observed the airplane lift off the runway, drift to the left, and disappear into the fog with the landing gear extended. They heard the engine running normally, with no change in sound, until the crash. They heard two distinct "booms" about 4 to 6 seconds apart. They ran down to the departure end of the runway to look for a crash site and could not see the wreckage or any smoke or fire due to the fog. The wreckage was located on elevated terrain in a heavily wooded area, about 1,500 feet north of the departure end of the runway. The elevation at the crash site was about 250 feet higher than the elevation at the departure end of runway. A swath through the treetops leading to the main wreckage was indicative of a near-level flight path at impact. An examination of the airframe and engine did not reveal any evidence of a preexisting mechanical malfunction or failure. A review of the weather by a NTSB meteorologist revealed that the departure airport was at the edge of an area of low-topped clouds. Airport remarks included "Mountainous terrain all quadrants."

The airplane had not been flown for about 5 months and the purpose of the accident flight was a maintenance test flight after both engines had been replaced with higher horsepower models. Witnesses observed the airplane depart and complete two uneventful touch-and-go landings. The airplane was then observed to be struggling to gain altitude and airspeed while maneuvering in the traffic pattern. One witness, who was an aircraft mechanic, reported that he observed the airplane yawing to the left and heard noises associated with propeller pitch changes, which he believed were consistent with the "Beta" range. The airplane stalled and impacted trees in a wooded marsh area, about 1 mile from the airport. It came to rest about 80-degrees vertically. Examination of the wreckage did not reveal any preimpact malfunctions; however, the lack of flight recorders and the condition of the wreckage precluded the gathering of additional relevant information. Damage observed to both engines and both propellers revealed they were likely operating at symmetrical power settings and blade angles at the time of the impact, with any differences in scoring signatures likely the result of impact damage. The reason for the yawing and the noise associated with propeller pitch changes that were reported prior to the stall could not be determined.