Robinson helicopters: mast bumping accidents in NZ

Mast bumping is contact between an inner part of a main rotor blade or a rotor hub and the main rotor drive shaft. The rotor design of Robinson helicopters means they are susceptible to mast bumping during low-G flight conditions. Low-G conditions can arise in turbulence. Significant areas of New Zealand terrain are mountainous, and they are often exposed to strong wind. Serious mast bumping that occurs in flight usually results in the helicopter breaking up during flight, which is fatal for those on board. This means it is often difficult to determine.