What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) Instructor pilot privacy data omitted (PIC) was training pilot privacy data omitted on an upcoming 135-check ride for the BHT-206-L3. Upon completion of the training flight both pilots observed buckling damage to the tailboom. The damage was located approximately 18 inches aft of the tailboom to fuselage mount point. The skin buckling is located from the 0130 position to the 0530 position on the right side of the tailboom and the 0700 position to the 1130 position on the left side of the tailboom. There was a one-inch long crack in the sheet-metal skin of the tailboom at the 1130 position approximately 18 inches aft of the mount point. The training flight took place late in the afternoon at approximately 1545-1600. The aircraft had just arrived from being repositioned from pne to owd. Prior to the flight the pic/instructor briefed on positive control transfer procedures. The training flight consisted of the following manuevers: pedal turns, hovers, hovering autorotations, and 2 autorotations one terminating at a hover and one autorotation terminating with a run on landing. During the autorotation terminating with a run on landing the PIC took over the controls without communicating with thestudent at approximately 12 feet AGL and completed the run-on landing. Both pilots were interviewed and did not feel there were any periods during the flight that would be considered to have incurred a hard landing. The director of operations for us helicopters inc. stated during telephone interviews that the aircraft had encountered severe turbulence during the repositioning flight from pne to owd and that was the reason for the tail-boom damage. During interviews with privacy data omitted the pilot who repositioned the helicopter from pne to owd he stated he is not aware how the damage could have happened, there was never a mention of severe turbulence during the pne to owd trip. Communication with Bell helicopter indicates that the damage apears similar to previous events that occurred a number of years back. "It was found that allowing the main rotor RPM to decay below 70% before the skids touch the ground in a touchdown autorotation can induce a "whirl mode" type vibration in the tailboom. If severe enough, this vibration can cause compression buckling in the tailboom skins." To address this problem, Bell helicopter issued operational safety notice 206L-84-10, which described the phenomenon and recommended that the skids be in ground contact before the main rotor decays below 70% during a touchdown autorotation. Also, a caution was added to the 206L-3 flight manual addressing this issue. The damage to the tailboom noted on N206PL at the completion of the training manuevers is consistent with the operational safety notice 206L-84-10.
As the FAA filed it
(-23) INSTRUCTOR PILOT ^PRIVACY DATA OMITTED^ (PIC) WAS TRAINING PILOT ^PRIVACY DATA OMITTED^ ON AN UPCOMING 135-CHECK RIDE FOR THE BHT-206-L3. UPON COMPLETION OF THE TRAINING FLIGHT BOTH PILOTS OBSERVED BUCKLING DAMAGE TO THE TAILBOOM. THE DAMAGE WAS LOCATED APPROXIMATELY 18 INCHES AFT OF THE TAILBOOM TO FUSELAGE MOUNT POINT. THE SKIN BUCKLING IS LOCATED FROM THE 0130 POSITION TO THE 0530 POSITION ON THE RIGHT SIDE OF THE TAILBOOM AND THE 0700 POSITION TO THE 1130 POSITION ON THE LEFT SIDE OF THE TAILBOOM. THERE WAS A ONE-INCH LONG CRACK IN THE SHEET-METAL SKIN OF THE TAILBOOM AT THE 1130 POSITION APPROXIMATELY 18 INCHES AFT OF THE MOUNT POINT. THE TRAINING FLIGHT TOOK PLACE LATE IN THE AFTERNOON AT APPROXIMATELY 1545-1600. THE AIRCRAFT HAD JUST ARRIVED FROM BEING REPOSITIONED FROM PNE TO OWD. PRIOR TO THE FLIGHT THE PIC/INSTRUCTOR BRIEFED ON POSITIVE CONTROL TRANSFER PROCEDURES. THE TRAINING FLIGHT CONSISTED OF THE FOLLOWING MANUEVERS: PEDAL TURNS, HOVERS, HOVERING AUTOROTATIONS, AND 2 AUTOROTATIONS ONE TERMINATING AT A HOVER AND ONE AUTOROTATION TERMINATING WITH A RUN ON LANDING. DURING THE AUTOROTATION TERMINATING WITH A RUN ON LANDING THE PIC TOOK OVER THE CONTROLS WITHOUT COMMUNICATING WITH THESTUDENT AT APPROXIMATELY 12 FEET AGL AND COMPLETED THE RUN-ON LANDING. BOTH PILOTS WERE INTERVIEWED AND DID NOT FEEL THERE WERE ANY PERIODS DURING THE FLIGHT THAT WOULD BE CONSIDERED TO HAVE INCURRED A HARD LANDING. THE DIRECTOR OF OPERATIONS FOR US HELICOPTERS INC. STATED DURING TELEPHONE INTERVIEWS THAT THE AIRCRAFT HAD ENCOUNTERED SEVERE TURBULENCE DURING THE REPOSITIONING FLIGHT FROM PNE TO OWD AND THAT WAS THE REASON FOR THE TAIL-BOOM DAMAGE. DURING INTERVIEWS WITH ^PRIVACY DATA OMITTED^ THE PILOT WHO REPOSITIONED THE HELICOPTER FROM PNE TO OWD HE STATED HE IS NOT AWARE HOW THE DAMAGE COULD HAVE HAPPENED, THERE WAS NEVER A MENTION OF SEVERE TURBULENCE DURING THE PNE TO OWD TRIP. COMMUNICATION WITH BELL HELICOPTER INDICATES THAT THE DAMAGE APEARS SIMILAR TO PREVIOUS EVENTS THAT OCCURRED A NUMBER OF YEARS BACK. "IT WAS FOUND THAT ALLOWING THE MAIN ROTOR RPM TO DECAY BELOW 70% BEFORE THE SKIDS TOUCH THE GROUND IN A TOUCHDOWN AUTOROTATION CAN INDUCE A "WHIRL MODE" TYPE VIBRATION IN THE TAILBOOM. IF SEVERE ENOUGH, THIS VIBRATION CAN CAUSE COMPRESSION BUCKLING IN THE TAILBOOM SKINS." TO ADDRESS THIS PROBLEM, BELL HELICOPTER ISSUED OPERATIONAL SAFETY NOTICE 206L-84-10, WHICH DESCRIBED THE PHENOMENON AND RECOMMENDED THAT THE SKIDS BE IN GROUND CONTACT BEFORE THE MAIN ROTOR DECAYS BELOW 70% DURING A TOUCHDOWN AUTOROTATION. ALSO, A CAUTION WAS ADDED TO THE 206L-3 FLIGHT MANUAL ADDRESSING THIS ISSUE. THE DAMAGE TO THE TAILBOOM NOTED ON N206PL AT THE COMPLETION OF THE TRAINING MANUEVERS IS CONSISTENT WITH THE OPERATIONAL SAFETY NOTICE 206L-84-10.