NTSB Identification: MIA07LA148
14 CFR Part 91: General Aviation
Accident occurred Wednesday, September 05, 2007 in Lakeland, FL
Probable Cause Approval Date: 11/25/2008
Aircraft: BELL 206B3, registration: N267MW
Injuries: 4 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
At the start of applying up collective for landing in the Bell 206B3 helicopter, the helicopter began an uncommanded yaw to the right due to failure of the No. 5 tail rotor driveshaft. The helicopter landed hard causing substantial damage to the fuselage structure near the left aft cross tube attach point. The forward fitting of the No.5 tail rotor drive shaft exhibited bond area separation between the splined adapter and the shaft, with subsequent rotation. Cream and green colored adhesives were noted at the seam at the aft edge of the splined adapter, and red colored compound similar to torque paint was noted in the area of the green colored adhesive. Disturbed adhesive and remnants of old clear coat was noted at the seam of the fixed coupling adapter on the aft end of the drive shaft. Disassembly inspection of the No. 5 tail rotor drive shaft driveshaft revealed rotational scoring on the outer surface of the shaft tube and inner surface of the splined adapter at the forward end of driveshaft assembly. In May 1999, the helicopter was involved in a tail rotor sudden stoppage which resulted in damage to at least one tail rotor blade, and tail rotor hub and blades being "…scrapped due to [tail rotor] sudden stoppage." The tail rotor driveshafts were not replaced at that time as required by the maintenance manual, and remained installed until 2004, when they were removed for inspection due to the occurrence in May 1999. The tail rotor drive shafts were inspected and approved for return to service in 2004, by the same facility that had scrapped the tail rotor blades in 1999, which is contrary to the maintenance manual. The driveshafts were reinstalled, and at the time of the accident, the No. 5 tail rotor driveshaft had accumulated 245.8 hours since inspection, and 4,087.4 hours since new. NTSB review of photographs of the tail rotor blades installed in May 1999, revealed evidence of buckling of the skin near the tip of both blades.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The failure of company maintenance personnel to replace the tail rotor drive shafts following tail rotor blade damage in 1999, the failure of maintenance personnel to replace the tail rotor drive shafts in 2004, following their knowledge that the tail rotor blades and hub were scrapped due to tail rotor blade damage, and improper inspection and return to service by an FAA approved repair station for their failure to condemn the tail rotor drive shafts in 2004, all of which resulted in failure of the No. 5 tail rotor drive shaft during approach for landing. Full narrative available
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