NTSB Identification: LAX02LA137.
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Accident occurred Sunday, April 14, 2002 in Scottsdale, AZ
Probable Cause Approval Date: 03/02/2004
Aircraft: Schweizer 269C, registration: N324PH
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The helicopter sustained substantial damage after experiencing a severe vibratory event during liftoff. The certified flight instructor (CFI) reported that the helicopter was positioned on a slope. The preflight and runup were uneventful. The engine was advanced to 3,100 rpm and the CFI instructed the student to bring the downslope skid level with the upslope skid. As the collective was raised, the helicopter began to vibrate. The CFI decreased engine power and control pressures. He then increased the engine speed to 3,100 rpm. As soon as pressure was placed on the controls, the helicopter began to "self destruct." The uphill skid did not leave the surface during either attempted takeoff. No unresolved mechanical discrepancies were noted with the helicopter prior to the accident. The helicopter was examined by an FAA airworthiness inspector. No preimpact discrepancies were noted with the main rotor dampers or the skid strut oleos. In the FAA Rotorcraft Flying Handbook (FAA-H-8083-21) it states that ground resonance is associated with fully articulated rotor systems. If a helicopter touches down on one corner, the blades may move out of their normal phase. If the rpm is in the normal operating range, the pilot should fly the helicopter off the ground, allowing the blades to automatically realign themselves. If not, the helicopter may self-destruct in a matter of seconds.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The flight instructor's inadequate remedial action following the onset of ground resonance.

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