The helicopter pilot reported that during the engine run-up sequence while on a movable helicopter pad attached to a tug, he noticed that the right rear door was not secure. The pilot unhooked his shoulder harness to reach back to secure the door. While attempting to reach the door, the pilot reported that he inadvertently applied right tail rotor pedal, which caused the helicopter to spin to the right multiple times. During the rotation the helicopter departed the movable pad, impacted the tug, and came to rest in an upright position on the ground. The helicopter sustained substantial damage to the vertical stabilizer.

The pilot reported there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.