Incident Overview
An instructor was conducting an employment evaluation for a pilot in a helicopter. The helicopter was positioned on a trailer during the evaluation.
Sequence of Events
During the startup procedure, the pilot prematurely applied full power. This caused the helicopter to rotate rapidly to the right in an uncontrolled manner. The helicopter's tail rotor struck a tractor that was attached to the trailer during the rotation. Following the impact, the helicopter continued to rotate until the main rotor assembly broke away from the helicopter, after which it came to rest a few feet from the trailer.
Damage
The tail rotor struck the tractor, and the main rotor assembly separated from the helicopter. The torque gauge in the helicopter indicated a reading in excess of 100%.