What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Gusty wind in area observed to dive into ground. Indicates main rotors flexed hit door and bubble prior crashing. (.4) witnesses reported hearing the aircraft fly overhead, then a 'schwap' sound, followed by silence. They looked up and saw the helicopter falling vertically to the ground. Postaccident investigation revealed that one main rotor blade had entered the cockpit through the left windshield half and cut the cabin floor aft to the left seat. The location of an indentation in the cyclic control crosstube, made by the rotor blade, corresponded to the cyclic control having been about in the full left control position. There was no evidence of a mechanical malfunction prior to the rotor divergence. A report of meteorological conditions by the safety board showed conditions conducive to mountain wave turbulence, and there were pilot reports of moderate to severe turbulence in the area of the accident. An AIRMET was in effect, calling for occasional moderate turbulence. The pilot did not receive a preflight weather briefing. The aircraft flight manual instructed the pilot to 'minimize cyclic control inputs in turbulence; do not overcontrol' and to land the aircraft 'as soon as practical.' A manufacturer's safety notice regarding flight in high winds or turbulence advised pilots 'do not overcontrol. Avoid large or abrupt controlmovements. Allow the aircraft to go with the turbulence, then restore level flight with smooth, gentle control inputs.' (-23) main rotor penetrated cockpit/left front.
As the FAA filed it
GUSTY WIND IN AREA OBSERVED TO DIVE INTO GROUND. INDICATES MAIN ROTORS FLEXED HIT DOOR AND BUBBLE PRIOR CRASHING. (.4) WITNESSES REPORTED HEARING THE AIRCRAFT FLY OVERHEAD, THEN A 'SCHWAP' SOUND, FOLLOWED BY SILENCE. THEY LOOKED UP AND SAW THE HELICOPTER FALLING VERTICALLY TO THE GROUND. POSTACCIDENT INVESTIGATION REVEALED THAT ONE MAIN ROTOR BLADE HAD ENTERED THE COCKPIT THROUGH THE LEFT WINDSHIELD HALF AND CUT THE CABIN FLOOR AFT TO THE LEFT SEAT. THE LOCATION OF AN INDENTATION IN THE CYCLIC CONTROL CROSSTUBE, MADE BY THE ROTOR BLADE, CORRESPONDED TO THE CYCLIC CONTROL HAVING BEEN ABOUT IN THE FULL LEFT CONTROL POSITION. THERE WAS NO EVIDENCE OF A MECHANICAL MALFUNCTION PRIOR TO THE ROTOR DIVERGENCE. A REPORT OF METEOROLOGICAL CONDITIONS BY THE SAFETY BOARD SHOWED CONDITIONS CONDUCIVE TO MOUNTAIN WAVE TURBULENCE, AND THERE WERE PILOT REPORTS OF MODERATE TO SEVERE TURBULENCE IN THE AREA OF THE ACCIDENT. AN AIRMET WAS IN EFFECT, CALLING FOR OCCASIONAL MODERATE TURBULENCE. THE PILOT DID NOT RECEIVE A PREFLIGHT WEATHER BRIEFING. THE AIRCRAFT FLIGHT MANUAL INSTRUCTED THE PILOT TO 'MINIMIZE CYCLIC CONTROL INPUTS IN TURBULENCE; DO NOT OVERCONTROL' AND TO LAND THE AIRCRAFT 'AS SOON AS PRACTICAL.' A MANUFACTURER'S SAFETY NOTICE REGARDING FLIGHT IN HIGH WINDS OR TURBULENCE ADVISED PILOTS 'DO NOT OVERCONTROL. AVOID LARGE OR ABRUPT CONTROLMOVEMENTS. ALLOW THE AIRCRAFT TO GO WITH THE TURBULENCE, THEN RESTORE LEVEL FLIGHT WITH SMOOTH, GENTLE CONTROL INPUTS.' (-23) MAIN ROTOR PENETRATED COCKPIT/LEFT FRONT.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.