05 March 2018
‘Severe vibrations’ caused in-flight breakup of Bell 525 prototype during OEI tests
The in-flight breakup of the first Bell 525 prototype was caused by unanticipated severe vibrations as the aircraft attempted to recover rotor rotation speed following a one-engine inoperative (OEI) test at 185 knots, the U.S. National Transportation Safety Board (NTSB) has found in its final report on the accident.
