NTSB Identification: CHI05LA218.
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Accident occurred Friday, August 05, 2005 in Goshen, IN
Probable Cause Approval Date: 02/28/2008
Aircraft: Enstrom 480, registration: N480FX
Injuries: 1 Serious,2 Minor.
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 certified flight instructor (CFI) stated that the student smoothly lowered the collective and set the helicopter on the ground as he was rolling off the throttle. The helicopter then started to bounce (ground resonance) and the CFI reached down to make sure the collective was down and the throttle was off. The helicopter continued to "shake violently and ripped itself apart." The helicopter had a new design of elastomeric damper installed 91 flight hours before the accident. The new design dampers had been flight tested at the factory and approved by the Federal Aviation Administration prior to being put into service. The helicopter had experienced severe vibrations on two previous flights, one of which resulted in the chin bubble being broken. Inspection of the accident dampers, at the damper manufacturer's factory, determined the dampers were within manufacturer's specifications. After the accident flight the helicopter manufacturer recalled all the new design elastomeric dampers.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: Ground resonance experienced by the pilots. Full narrative available
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