What happened
Shortly after takeoff, while climbing through 200 feet, the engine RPM of the aircraft decreased to 1,500 RPM. The pilot attempted to adjust the throttle settings, but these changes had no effect on the engine performance. Unable to maintain altitude, the pilot maneuvered the aircraft for a forced landing at a nearby sod farm.
During the landing sequence, the airplane stalled and struck the ground hard just short of the intended touchdown location, subsequently nosed over. The occupants were not injured.
The investigation
An FAA Airworthiness Inspector examined the engine and aircraft, discovering that the fuel selector valve had been improperly assembled, as no detents could be felt during operation.
Testing of the engine revealed low cold differential compression readings for several cylinders: cylinder No. 1 recorded 20 psi, No. 2 recorded 19 psi, No. 3 recorded 54 psi, and No. 4 recorded 5 psi. Following an adjustment of the valves on cylinder No. 2, the compression reading increased to over 50 psi.
The investigation also identified fire damage on the backside of the induction air filter assembly. Additionally, the carburetor was found to contain a two-piece venturi, despite an airworthiness directive requiring a one-piece venturi. Although maintenance records indicated that a one-piece venturi had been installed, the physical component did not match the documentation. Records also showed that the rocker arms had been adjusted on April 21, 1997, with approximately 85 flight hours accumulated since that service.