What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
During sequential hovering to track main rotor blades, aircraft was difficult to control. PIC reported cyclic moving in a semicircular motion periodically in a time sequence. I watched a video taken prior to accident flight, which appeared to have blade out of phase in a one-per-rev pattern.
Nearing dusk, PIC was not sure what happened, as ground contact was made, impact of blade with fence and hard landing with ground and obstacles. Aircraft moved forward-ish and turning left about couple hundred feet, as it appeared a week later.
PIC stated to investigator he had known something was wrong and after 89 hours, he had not yet taken his family for a ride, as they tried to correct the vibration and control issues.
Manufacturer reportedly told him to track the blades. He was tracking blades using little led lights on the blade tip areas.
Another owner reportedly told him it was the dampers needing correction.
One article in privacy data omitted by another owner builder, who visited privacy data omitted also; showed a multiple blade damper change sequence of all main rotor dampers more than once trying to resolve similar.
In that helicopter, the assistance from the manufacturer removed all dampers and the entire rotor hub and brought it back much later and then used a privacy data omitted electronic track and balance apparatus to improve that one and adjust the dampers for proper phasing and operation.
As the FAA filed it
DURING SEQUENTIAL HOVERING TO TRACK MAIN ROTOR BLADES, AIRCRAFT WAS DIFFICULT TO CONTROL. PIC REPORTED CYCLIC MOVING IN A SEMICIRCULAR MOTION PERIODICALLY IN A TIME SEQUENCE. I WATCHED A VIDEO TAKEN PRIOR TO ACCIDENT FLIGHT, WHICH APPEARED TO HAVE BLADE OUT OF PHASE IN A ONE-PER-REV PATTERN.
NEARING DUSK, PIC WAS NOT SURE WHAT HAPPENED, AS GROUND CONTACT WAS MADE, IMPACT OF BLADE WITH FENCE AND HARD LANDING WITH GROUND AND OBSTACLES. AIRCRAFT MOVED FORWARD-ISH AND TURNING LEFT ABOUT COUPLE HUNDRED FEET, AS IT APPEARED A WEEK LATER.
PIC STATED TO INVESTIGATOR HE HAD KNOWN SOMETHING WAS WRONG AND AFTER 89 HOURS, HE HAD NOT YET TAKEN HIS FAMILY FOR A RIDE, AS THEY TRIED TO CORRECT THE VIBRATION AND CONTROL ISSUES.
MANUFACTURER REPORTEDLY TOLD HIM TO TRACK THE BLADES. HE WAS TRACKING BLADES USING LITTLE LED LIGHTS ON THE BLADE TIP AREAS.
ANOTHER OWNER REPORTEDLY TOLD HIM IT WAS THE DAMPERS NEEDING CORRECTION.
ONE ARTICLE IN ^PRIVACY DATA OMITTED^ BY ANOTHER OWNER BUILDER, WHO VISITED ^PRIVACY DATA OMITTED^ ALSO; SHOWED A MULTIPLE BLADE DAMPER CHANGE SEQUENCE OF ALL MAIN ROTOR DAMPERS MORE THAN ONCE TRYING TO RESOLVE SIMILAR.
IN THAT HELICOPTER, THE ASSISTANCE FROM THE MANUFACTURER REMOVED ALL DAMPERS AND THE ENTIRE ROTOR HUB AND BROUGHT IT BACK MUCH LATER AND THEN USED A ^PRIVACY DATA OMITTED^ ELECTRONIC TRACK AND BALANCE APPARATUS TO IMPROVE THAT ONE AND ADJUST THE DAMPERS FOR PROPER PHASING AND OPERATION.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.