What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) During aerial application, the rotorcraft experienced loss of tail rotor authority. Further investigation revealed that all hangar bearings, spline-coupling shafts and gearing (output quill) from the transmission to the tail rotor gearbox appeared to be without damage or any overheating condition. There was a crack on the tail boom frame that was considered suspect to the accident. This small segment of the tail boom frame was removed for further visual analysis, which confirmed a dark outline of rust indicating a long time crack. Additionally, it was noted that the cross-over support tube was missing in that portion of the tail boom frame. This would explain the crack that generated on this portion of the frame due to the excessive torque being applied during pedal turns.
As the FAA filed it
(-23) DURING AERIAL APPLICATION, THE ROTORCRAFT EXPERIENCED LOSS OF TAIL ROTOR AUTHORITY. FURTHER INVESTIGATION REVEALED THAT ALL HANGAR BEARINGS, SPLINE-COUPLING SHAFTS AND GEARING (OUTPUT QUILL) FROM THE TRANSMISSION TO THE TAIL ROTOR GEARBOX APPEARED TO BE WITHOUT DAMAGE OR ANY OVERHEATING CONDITION. THERE WAS A CRACK ON THE TAIL BOOM FRAME THAT WAS CONSIDERED SUSPECT TO THE ACCIDENT. THIS SMALL SEGMENT OF THE TAIL BOOM FRAME WAS REMOVED FOR FURTHER VISUAL ANALYSIS, WHICH CONFIRMED A DARK OUTLINE OF RUST INDICATING A LONG TIME CRACK. ADDITIONALLY, IT WAS NOTED THAT THE CROSS-OVER SUPPORT TUBE WAS MISSING IN THAT PORTION OF THE TAIL BOOM FRAME. THIS WOULD EXPLAIN THE CRACK THAT GENERATED ON THIS PORTION OF THE FRAME DUE TO THE EXCESSIVE TORQUE BEING APPLIED DURING PEDAL TURNS.
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 N7NB · 1
Matched to the same aircraft by N-number and date.