What happened
During the approach for landing, approximately four feet above ground level, the stall warning horn activated. In response, the commercial pilot abruptly reduced engine power. This caused the aircraft to descend rapidly, touching down in a nose-high attitude slightly left of the runway centerline.
Following touchdown, the commercial pilot applied full power, which caused the aircraft to veer further to the left. The flight instructor then took control of the aircraft to attempt to regain the runway heading. Unaware that full power had been applied, the instructor instructed the pilot to reduce power. Although the power was reduced, the aircraft exited the runway surface and traveled over gravel and snow.
During the excursion, the right wing struck a taxi sign. This collision caused the outboard section of the right wing flap to separate at the two outboard hinges, and the right main landing gear tire separated from its gear leg. The crew members were not injured.
Findings
The investigation noted that both pilots reported no mechanical failures or malfunctions with the aircraft prior to the accident.