What happened
During the takeoff roll, the pilot of N916TM, a Beech 18, reported that the aircraft achieved liftoff at a speed of 70 knots. While accelerating within ground effect, the aircraft began to exhibit instability in the roll axis. In an attempt to correct the instability, the pilot increased engine power.
As the aircraft continued down the runway, the left wingtip made contact with the pavement roughly three-quarters of the way through the takeoff roll. The pilot applied further power, which led to the left wing striking the grass area located on the left side of the departure end of the runway. Following this contact, the pilot reduced the engines to idle and brought the aircraft to a stop in the grass. The impact caused the landing gear to collapse. The pilot noted that the engines appeared to be operating normally during the entire sequence of events.
Findings
An investigation into the incident revealed that another Beech 18 had departed from the same runway in the opposite direction less than one minute before the accident involving N916TM.