What happened
An airline transport certificated pilot was performing a photo flight in a helicopter over mountain terrain covered in snow. While maneuvering along a ridge line, the pilot entered an area where the end of the ridge was obscured by shadow.
While flying through this shadowed area, the pilot experienced a loss of depth perception. In an attempt to move the aircraft away from the ridge, the pilot increased engine power. During this maneuver, the left landing gear skid tube made contact with the snow on the ridge, causing the pilot to feel a vibration. The pilot subsequently performed an emergency landing on lower terrain and shut down the engines.
The investigation
A post-flight inspection of the aircraft was conducted to assess the impact of the contact with the snow. The inspection revealed internal damage to the tail rotor spars and a torsional twist in the tail rotor drive shaft.