Lakeland, FL, USA
N267MW
BELL 206B3
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.
On September 5, 2007, about 1515 eastern daylight time, a Bell 206B3, N267MW, registered to and operated by Tiger Aviation Sales, LLC, experienced a tail rotor drive shaft failure and subsequent hard landing at Lakeland Linder Regional Airport (KLAL), Lakeland, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 business flight from a construction site located in Oldsmar, Florida, to LAL. The helicopter was substantially damaged and the commercial-certificated pilot and three passengers were not injured. The flight originated about 1445, from Oldsmar, Florida. After takeoff the flight proceeded to the destination and the pilot later stated that while on short final approach at the start of applying up collective, the nose of the helicopter yawed uncommanded to the right. He applied full left anti-torque pedal input which had no effect. After yawing 360 degrees, he realized he had a tail rotor failure and rolled the throttle to idle. The helicopter continued yawing to the right, contacted the ground while yawing, bounced two or three times, and came to rest upright. Examination of the helicopter by a Federal Aviation Administration (FAA) airworthiness inspector revealed no damage to the tail rotor blades. Structural damage to the fuselage in the area of the left aft cross tube attach point was noted. The main rotor blades were rotated by hand and tail rotor drive continuity was confirmed to the tail rotor blades. The tail rotor blades were then held stationary and the main rotor blades were then rotated in the normal direction of rotation. A "popping or cracking" sound was noted at the forward fitting of the No.5 tail rotor drive shaft; evidence of heat discoloration was noted on the exterior surface of the forward fitting of the #5 tail rotor drive shaft. The No. 5 tail rotor drive shaft and hanger bearing assembly (P/N 206-040-930-9, S/N VNMA-07662) were retained by NTSB for further examination at Bell Helicopter with FAA oversight. Visual inspection of the No. 5 tail rotor drive shaft revealed the seam at the aft edge of the splined adapter showed a cream colored adhesive covering along most of the seam, with dark green colored adhesive covering approximately 135 degrees circumferentially. The area around the green adhesive also showed a red colored compound similar to torque paint. X-Ray inspection of the No. 5 tail rotor drive shaft before disassembly revealed gaps between the splined adapter and shaft tube, and also bond area separation between the splined adapter and the shaft at the forward end of the shaft, with subsequent rotation. The aft flanged adapter on shaft exhibited disturbed adhesive and remnants of old clear coat, and also evidence that the clear coat was repaired or replaced at some earlier time. Following removal of the splined adapter and shaft, discoloration of the adhesive material used to bond the two was noted, and rotational scoring was noted on the outer surface of the shaft tube and inner surface of the splined adapter at the forward end of drive shaft assembly. Red colored torque paint though not required during manufacturing, nor a common practice, was found on the tube shaft and splined coupler at the forward end of the drive shaft assembly. The two adhesives found were both similar to the required adhesive in the main bond area and also to the adhesive required to fill pin holes on the edge of the bond joint. Detailed examination of the main bond area revealed a discolored area where the bond adhesive fractured from the base material. In addition, corrosion pitting was noted on the inner surface of the splined adapter. Dimensional and hardness checks revealed no substantial discrepancies. Research revealed that on or about May 5, 1999, tail rotor blade contact with sage brush occurred during an unknown phase of flight during a 14 CFR Part 135 on-demand flight. The helicopter was then flown uneventfully from the occurrence location (Flagstaff, Arizona) to Scottsdale, Arizona, where an entry in the Helicopter Log dated May 5, 1999, indicates, "[tail rotor] found on post flight with damage." The tail rotor hub and blades were "…scrapped due to [tail rotor] sudden stoppage", and new tail rotor hub and blades were installed. The mechanic who made the May 5, 1999, entry reported he did not personally see the tail rotor blades because he was out of state at the time. He was told however that the tip of one blade may have been bent and the skin was scraped. The tail rotor drive shafts remained in the helicopter until 2004, when the new helicopter owner insisted they be inspected after finding out about the May 1999, occurrence. The tail rotor drive shafts were removed and sent to an FAA approved repair station, which was the same facility that had scrapped the tail rotor hub and tail rotor blades in May 1999, due to "...[tail rotor] sudden stoppage." Records provided by the FAA approved repair station that inspected the tail rotor drive shafts in 2004 indicates they, "Complied with conditional inspections and overhaul requirements on 4 [each] Driveshafts P/N 206-040-931-009 S/N's VNMA 07662..." which included visual and zyglo inspections. The tail rotor drive shafts were re-installed, and had accumulated 245.8 hours and 4,087.4 hours since the conditional inspection and since new respectively, at the time of the failure of the No. 5 drive shaft. Section 5-35 titled "SUDDEN STOPPAGE/ACCELERATION - TAIL ROTOR" of the helicopter maintenance manual (MM) provides the definition of "SUDDEN STOPPAGE/ACCELERATION" and lists maintenance actions to be performed or accomplished pertaining to sudden stoppage/acceleration of the tail rotor. Item 3 of the 13 item list indicates to inspect all tail rotor drive shafts using magnetic particle or fluorescent penetrate methods, while item 7 of the list indicates, "...ALL bonded tail rotor drive shafts shall be considered unserviceable and scrapped, if during a sudden stoppage inspection any of [the] following conditions which are attributable to sudden stoppage are noted" with Item 7a indicating, "Any impact damage to a tail rotor blade leading edge or skin, or any tail rotor blade skin buckling or tears." The helicopter owner at the time of the occurrence in May 1999, retained the tail rotor blades which were removed following the May 1999 occurrence. A friend of the owner inspected both tail rotor blades and reported that the skin on one side of one tail rotor blade exhibited palm sized damage. NTSB review of pictures of the tail rotor blades revealed slight buckling of the skin near the tip of both blades. The leading edges of both blades did not have any apparent damage.
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.
Source: NTSB Aviation Accident Database
Aviation Accidents App
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