Incident Description
A student pilot was attempting to bring a helicopter to a hover while an instructor watched from outside the helicopter. During the attempt, the left skid was in the air and the entire right skid remained on the ground. Subsequently, the helicopter rolled over.
Pilot Experience
The student pilot had a total of 27 hours of flight experience, all of which were in helicopters.
Investigation Findings
Investigators found no pre-impact failures or malfunctions. The Federal Aviation Administration Advisory Circular 90-87 (Helicopter Dynamic Rollover) provides relevant information: "During normal or slope takeoffs and landings with...one skid/wheel on the ground, the bank angle or side drift can place the helicopter in a situation where it is pivoting (rolling) about a skid/wheel which is still in contact with the ground....if a roll rate is permitted to develop, a critical bank angle...may be reached where roll cannot be corrected, even with full lateral cyclic."