Incident Overview
Shortly after takeoff, the aircraft experienced a partial loss of engine power. The pilot was unable to maintain altitude and airspeed. Due to the low airspeed, the pilot could not retract the landing gear because the automatic gear extension system was not set to the override position. Normal flight operations do not utilize the gear override feature.
Sequence of Events
The aircraft cleared trees at the departure end of the runway and subsequently descended onto a boat dock and then to the ground.
Findings
Post-accident examination revealed that four out of the six top spark plugs were not firing. At the time of the accident, the density altitude was calculated to be about 6,200 feet.
Operational Details
The automatic gear extension system, which extends the landing gear at low airspeeds, remained in its normal operating mode (not overridden). The pilot was unable to retract the gear due to the low airspeed, which likely increased drag and hindered climb performance.
Conclusion
The investigation documented these facts without attributing a specific probable cause.