Incident Overview
A C-47 aircraft was conducting a survey flight at an altitude of 400 feet above ground level (AGL) when an oil leak was observed in the number 2 (right) engine. In response, the crew feathered the propeller of that engine and increased power on the number 1 (left) engine.
Sequence of Events
Shortly after increasing power, the propeller of the left engine ran away, creating additional drag. The crew attempted to unfeather the right engine to restore power, but these attempts were unsuccessful. The aircraft subsequently struck the ground.
Probable Cause
According to the official investigation, the right engine appears to have been feathered unnecessarily and in too much of a hurry, given that the aircraft was only 400 feet above the ground. When power was increased on the left engine, its propeller became uncontrollable due to a failure of the propeller governor or a deficient screen in the oil strainer. This necessitated feathering the left engine as well, leaving the aircraft without any power and resulting in an immediate forced landing.