THE US NATIONAL Transportation Safety Board (NTSB) recommends immediate and recurring inspections for cracks in the tail booms of certain Bell 206L (LongRanger) helicopters.
The NTSB urges the US Federal Aviation Administration to act after probing the 4 April crash of a Bell 206L-1 near Charleston, West Virginia, in which the pilot and passenger were killed.
According to the NTSB, the aircraft, operated by the West Virginia State Police, suffered an in-flight break-up. Examination of the wreckage revealed that the tail assembly, which included the vertical stabiliser and the tail-rotor gearbox, had separated from the tail boom, confirming eye-witness reports. Evidence of pre-existing cracking in the tail boom was found.
Discovery of tail-boom cracks in 206L-series aircraft prompted Bell to begin installing doublers (reinforcement sheets riveted to the skin), beginning with the 206L-4.
The NTSB believes that 206L, L-1 and L-3 models without a doubler in the gearbox-fairing attachment are sus ceptible to premature fatigue cracking and should undergo immediate and periodic inspections, adding that the 100h inspection interval should be halved.
Source: Flight International
