From flightglobal :
" Bell Helicopter lost the testbed aircraft for the transmission system of the company's new 525R Relentless in a crash on 7 August in Avalon, Texas.
The Bell 214ST (N409SB) had just completed a right turn when the flightcrew reported hearing a "bang", according to a preliminary report filed with the US National Transportation Safety Board. The chase aircraft informed the crew that "something had departed the tail of the helicopter", the NTSB says. The 214ST crew autorotated to land in a field nearby, but the helicopter "yawed and rolled right on landing". The flightcrew was not injured in the accident.
The Bell 214ST is used by the company for research and development flights. It was assigned to perform risk reduction tests for the transmission system on the Bell 525R, a super-medium twin."
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