Incident Overview
A twin-engine airplane operating under FAR Part 135 experienced a partial loss of power to both engines during cruise flight, resulting in a forced landing to a field. The aircraft sustained minor damage when the landing gear collapsed during the rollout.
Flight Details
The flight was en route to an airport approximately 70 miles from the departure airport. While climbing through 5,600 feet msl, the right engine began running rough, and its manifold air pressure (MAP) dropped to 18 inches. The pilot did not secure the right engine, as it was still producing some power, and compensated by increasing the left engine's MAP to 35 inches. At that time, the airplane was about 25–30 miles from the departure airport, but the pilot continued toward the destination.
Engine Failure and Forced Landing
Approximately 20 miles from the destination airport, the left engine also began running rough, and its MAP quickly dropped to 18 inches. The pilot executed a forced landing to a field about nine miles from the destination airport. According to the pilot, after assuring that the airport could not be reached, both engines were secured, and the best available landing site was selected. The landing gear was lowered after engine shutdown. The airplane touched down in the middle of a field; the landing gear collapsed during the rollout, and the airplane skidded to a stop on its belly.
Post-Incident Inspection and Engine Tests
An inspection of the fuel system and engines revealed no anomalies. The fuel tanks contained fuel, and no contamination was found. Both engines were started for ground runs: the left engine operated normally, while the right engine could only develop 30–32 inches of MAP. After the oil line to the right engine's waste gate differential control was capped off, the engine produced 40 inches of MAP. The FAA approved a ferry flight; the airplane departed and flew for 30 minutes in the local pattern before continuing to Denver without incident or engine anomalies. An uncontrolled airport with lighted runways was located 30 miles from the departure airport and 40 miles from the destination airport.