Accident Overview
The pilot of a Beech 18, registration N916TM, reported that during takeoff the airplane lifted off at 70 knots. After accelerating in ground effect, the airplane became 'unstable in the roll axis,' prompting the pilot to add power. The left wing tip then contacted the runway approximately three-quarters of the way down the runway. The pilot added additional power, after which the left wing contacted the grass off the left side of the departure end of the runway. The pilot subsequently reduced power to idle and landed the airplane in the grass, collapsing the landing gear.
Pilot and Aircraft Information
The pilot noted that the engines sounded normal throughout the accident sequence. The investigation revealed that another Beech 18 had taken off on the same runway, but in the opposite direction of N916TM, less than one minute prior to the accident.
Probable Cause
According to the official findings, the probable cause was the pilot's failure to identify the unsafe condition (vortex turbulence) which existed due to the departing airplane and his subsequent inability to control the airplane once encountering the turbulence.