What happened
On March 30, 2013, at 1300 local time, a Robinson R22 Beta II, registration ZK-HIE, was conducting an instructional flight near New Plymouth, New Zealand. During maneuvers, the aircraft experienced a sudden pitch down and a roll to the right.
The crew, consisting of a student pilot and a certified flight instructor, were not injured. The pilot was able to regain control of the helicopter and completed the flight by landing without further incident.
While the landing was successful, the maneuver caused mast bumping, which resulted in damage to the aircraft. The damage was significant enough to require the replacement of numerous components within the main rotor system.