Accident Details
On final approach to Grand Canyon-National Park Airport, the right engine partially failed. The pilot feathered the propeller of the affected engine. The airplane subsequently lost height and crashed on a plateau located several miles from the airport. The pilot and four passengers were killed, while four other occupants sustained serious injuries.
Probable Cause
The official probable cause of the accident was that the airplane crashed on a plateau following improper operation of powerplant and powerplant controls.
Contributing Factors
Investigators reported several contributing factors: failure to follow approved procedures, improper emergency procedures, issues with the lubrication system including lines, hoses, and fittings, leakage, rough terrain, a forced landing off airport on land, oil leakage on the right engine, the propeller feathered, no malfunction found, and failure to boost the left engine power.