Accident Details
The pilot and a prospective buyer/passenger were on a local demonstration flight. Prior to this flight, the aircraft had been parked for nearly one year and had flown only 66 hours since its last annual inspection. During the preflight inspection, the pilot found the fuel tanks between 1/4 full and empty. The sumps were drained, the main tanks were filled, then the sumps were drained again.
After takeoff, the pilot leveled the aircraft at 1,500 feet in a cruise configuration. Shortly thereafter, the left engine began running rough, backfiring, and losing power. The pilot turned back toward the airport, but the engine lost all power and the propeller was feathered. While returning, the right engine's cylinder head and oil temperature began rising above the red line. Subsequently, it began losing power, and a wheels-up, forced landing was made in an open field.
Examination
An examination revealed that both engines were out of time, firing was intermittent, and the distributor block on the left engine was burned due to incorrect timing. Additionally, the left turbocharger gate was stuck open, and the left fuel filter was partially clogged.
Probable Cause
The probable cause was determined as occurrence #1: loss of engine power (partial) due to mechanical failure/malfunction. Findings included: inadequate maintenance by other maintenance personnel; incorrect magneto ignition timing; improper adjustment; distributor arcing; partially blocked fuel filter; fuel starvation; binding of the turbocharger; and partial failure of two or more engines.