What happened
While operating in cruise flight at 23,000 feet MSL, the pilot of the aircraft heard a medium loud pop approximately one hour into the flight. Following this sound, there was an immediate drop in manifold pressure to approximately 15 inches. The pilot initially believed the turbocharger had failed and anticipated that engine power would return once the aircraft descended below 10,000 feet. However, the engine power did not recover, prompting the pilot to execute a forced landing into a muddy pasture.
The aircraft sustained substantial damage to the fuselage, engine firewall, and landing gear during the landing.
The investigation
Two FAA safety inspectors conducted an on-scene examination of the aircraft and the engine. During the recovery of the aircraft, approximately 90 gallons of blue aviation fuel were drained from both wing tanks and their respective collector/sump tanks located at the wing roots. Inspectors found approximately one quart of water drained from both the left and right wing collector/sump tanks, which each have a capacity of one U.S. gallon.
The engine was test-run on the airframe using the existing fuel system. Due to cool outside air temperatures, the engine required priming before starting. Once running, the engine was operated through various power settings and ran continuously without interruption. The magnetos functioned normally, and all engine gauge readings remained normal. The pilot noted that a preflight inspection, which included draining both collector/sump tanks, had been performed and no water was detected in the fuel at that time.
Findings
An examination of the engine, accessories, and fuel system revealed no mechanical deficiencies that could have contributed to the loss of power.