What happened
During the takeoff phase, a helicopter experienced a severe vibratory event immediately after liftoff was attempted. The certified flight instructor (CFI) reported that the aircraft was positioned on a slope during the operation. While the preflight and runup procedures were uneventful, the engine was advanced to 3,100 rpm.
The CFI instructed the student pilot to level the downslope skid with the upslope skid. As the collective was raised, the helicopter began to vibrate. In an attempt to stabilize the aircraft, the CFI decreased engine power and control pressures before increasing the engine speed back to 3,100 rpm. However, as soon as pressure was applied to the controls, the helicopter entered a state of intense vibration described by the instructor as "self destruct." Throughout both attempted takeoffs, the uphill skid remained in contact with the surface.
The investigation
The aircraft sustained substantial damage during the event. An FAA airworthiness inspector examined the helicopter and found no unresolved mechanical discrepancies prior to the accident. Specifically, no preimpact discrepancies were noted regarding the skid strut oleos or the main rotor dampers.