What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) During a practice "autorotation" maneuver the collective was lowered to approximately 2/3 down when, the helicopter experienced a severe vertical 1:1 vibration. Increasing or decreasing power, or inputting of cyclic roll or pitch, would not decrease vibration. The vibration subsided with the collective "bottomed-out". During the flare, when the collective was raised for power, the vibration returned which resulted in a hard landing. A preliminary inspection revealed warped tail boom, dents in the leading edge of the tail rotor blades, bent aft skid cross tube, cracks in the main rotor transmission support, and a 1/4 inch separation between mast retaining plate and the upper transmission case. A review of the maintenance records provided does not indicate a probable cause for the vibration. The post accident inspection by an outside company indicates, several control bearings worn which cummutativity may have induced a vertical vibration. The interviews with the director of maintenance and the pilot, indicate no history of maintenance problems since this aircraft was released from a heavy maintenance visit approximately 30 hours prior to the accident.
As the FAA filed it
(-23) DURING A PRACTICE "AUTOROTATION" MANEUVER THE COLLECTIVE WAS LOWERED TO APPROXIMATELY 2/3 DOWN WHEN, THE HELICOPTER EXPERIENCED A SEVERE VERTICAL 1:1 VIBRATION. INCREASING OR DECREASING POWER, OR INPUTTING OF CYCLIC ROLL OR PITCH, WOULD NOT DECREASE VIBRATION. THE VIBRATION SUBSIDED WITH THE COLLECTIVE "BOTTOMED-OUT". DURING THE FLARE, WHEN THE COLLECTIVE WAS RAISED FOR POWER, THE VIBRATION RETURNED WHICH RESULTED IN A HARD LANDING. A PRELIMINARY INSPECTION REVEALED WARPED TAIL BOOM, DENTS IN THE LEADING EDGE OF THE TAIL ROTOR BLADES, BENT AFT SKID CROSS TUBE, CRACKS IN THE MAIN ROTOR TRANSMISSION SUPPORT, AND A 1/4 INCH SEPARATION BETWEEN MAST RETAINING PLATE AND THE UPPER TRANSMISSION CASE. A REVIEW OF THE MAINTENANCE RECORDS PROVIDED DOES NOT INDICATE A PROBABLE CAUSE FOR THE VIBRATION. THE POST ACCIDENT INSPECTION BY AN OUTSIDE COMPANY INDICATES, SEVERAL CONTROL BEARINGS WORN WHICH CUMMUTATIVITY MAY HAVE INDUCED A VERTICAL VIBRATION. THE INTERVIEWS WITH THE DIRECTOR OF MAINTENANCE AND THE PILOT, INDICATE NO HISTORY OF MAINTENANCE PROBLEMS SINCE THIS AIRCRAFT WAS RELEASED FROM A HEAVY MAINTENANCE VISIT APPROXIMATELY 30 HOURS PRIOR TO THE ACCIDENT.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.
Other reports on N64RA · 1
Matched to the same aircraft by N-number and date.