What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) The aircraft was being operated as a public aircraft contracted by the us dept of interior/blm. After landing on a rocky outcrop the pilot lowered the collective. Just as the collective was completely lowered the pilot was going to instruct the occupants to deplane, however just at that moment the aircraft began a somewhat gentle gyrating motion and the pilot decided ground resonance could develop if he did not raise the collective and get airborne. Just as he began to raise the collective the aircraft began a series of very violent motions. The entire sequence took only about 2 seconds. At least one main rotor impacted the cabin roof and struck the helmets of the rear seat passengers. Two passengers complained of some strained muscles and one passenger sustained a non-life threatening head injury. The tail-boom was severed just forward of the tail-rotor gear box, the main transmission was ripped up and out of the helicopter, coming to rest a few feet to the right side of the helicopter with the main rotorblades still attached. An on-site investigation was conducted on 12/16/05 by the usdoi and an FAA ASI. No conclusion was reached as to probable cause. (-23 amendment) 02/08 and 09/2006, a team consisting of 2 inspectors from doi/amd a Eurocopter rep. FAA iic privacy data omitted and asi/pmi privacy data omitted conducted an investigation of the wreckage inside a hangar at kcdc. The investigation did not seem to pin point or divulge any outstanding single failure or cause. There were some questions raised as to the main strut pressures and the differences. The team spent much time inspecting the maintenance records and some questions were raised. The general consensus appeared to point towards ground resonance as the cause but what induced the resonance may not be determined due to the extent of poor condition and absence of numerous components. In that this accident is a public aircraft accident and the controlling govt agency has jurisdiction, the FAA iic determined to not devote extraordinary time and resources in addition to the doi/amd investigator's. when a probable cause and other factors are made public the FAA will address, as necessary any issues which are determined relevant.
As the FAA filed it
(-23) THE AIRCRAFT WAS BEING OPERATED AS A PUBLIC AIRCRAFT CONTRACTED BY THE US DEPT OF INTERIOR/BLM. AFTER LANDING ON A ROCKY OUTCROP THE PILOT LOWERED THE COLLECTIVE. JUST AS THE COLLECTIVE WAS COMPLETELY LOWERED THE PILOT WAS GOING TO INSTRUCT THE OCCUPANTS TO DEPLANE, HOWEVER JUST AT THAT MOMENT THE AIRCRAFT BEGAN A SOMEWHAT GENTLE GYRATING MOTION AND THE PILOT DECIDED GROUND RESONANCE COULD DEVELOP IF HE DID NOT RAISE THE COLLECTIVE AND GET AIRBORNE. JUST AS HE BEGAN TO RAISE THE COLLECTIVE THE AIRCRAFT BEGAN A SERIES OF VERY VIOLENT MOTIONS. THE ENTIRE SEQUENCE TOOK ONLY ABOUT 2 SECONDS. AT LEAST ONE MAIN ROTOR IMPACTED THE CABIN ROOF AND STRUCK THE HELMETS OF THE REAR SEAT PASSENGERS. TWO PASSENGERS COMPLAINED OF SOME STRAINED MUSCLES AND ONE PASSENGER SUSTAINED A NON-LIFE THREATENING HEAD INJURY. THE TAIL-BOOM WAS SEVERED JUST FORWARD OF THE TAIL-ROTOR GEAR BOX, THE MAIN TRANSMISSION WAS RIPPED UP AND OUT OF THE HELICOPTER, COMING TO REST A FEW FEET TO THE RIGHT SIDE OF THE HELICOPTER WITH THE MAIN ROTORBLADES STILL ATTACHED. AN ON-SITE INVESTIGATION WAS CONDUCTED ON 12/16/05 BY THE USDOI AND AN FAA ASI. NO CONCLUSION WAS REACHED AS TO PROBABLE CAUSE. (-23 AMENDMENT) 02/08 AND 09/2006, A TEAM CONSISTING OF 2 INSPECTORS FROM DOI/AMD A EUROCOPTER REP. FAA IIC ^PRIVACY DATA OMITTED^ AND ASI/PMI ^PRIVACY DATA OMITTED^ CONDUCTED AN INVESTIGATION OF THE WRECKAGE INSIDE A HANGAR AT KCDC. THE INVESTIGATION DID NOT SEEM TO PIN POINT OR DIVULGE ANY OUTSTANDING SINGLE FAILURE OR CAUSE. THERE WERE SOME QUESTIONS RAISED AS TO THE MAIN STRUT PRESSURES AND THE DIFFERENCES. THE TEAM SPENT MUCH TIME INSPECTING THE MAINTENANCE RECORDS AND SOME QUESTIONS WERE RAISED. THE GENERAL CONSENSUS APPEARED TO POINT TOWARDS GROUND RESONANCE AS THE CAUSE BUT WHAT INDUCED THE RESONANCE MAY NOT BE DETERMINED DUE TO THE EXTENT OF POOR CONDITION AND ABSENCE OF NUMEROUS COMPONENTS. IN THAT THIS ACCIDENT IS A PUBLIC AIRCRAFT ACCIDENT AND THE CONTROLLING GOVT AGENCY HAS JURISDICTION, THE FAA IIC DETERMINED TO NOT DEVOTE EXTRAORDINARY TIME AND RESOURCES IN ADDITION TO THE DOI/AMD INVESTIGATOR'S. WHEN A PROBABLE CAUSE AND OTHER FACTORS ARE MADE PUBLIC THE FAA WILL ADDRESS, AS NECESSARY ANY ISSUES WHICH ARE DETERMINED RELEVANT.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.