NTSB targets Rolls-Royce helicopter engine FADEC
The ongoing investigation into the fatal crash of a Bell 407 following a loss of engine power during a low-altitude hover has prompted the NTSB to ask the FAA to address an allegedly “catastrophic failure mode” with the full-authority digital electronic control (FADEC) system. The Safety Board said post-accident investigation revealed that, with the FADEC in automatic mode, the Model 250 engine ran erratically and at times lost power when the throttle was advanced. Also, a hard-fault failure of the most likely culprit–erratic signals from the FADEC’s potentiometer–does not generate a warning in the cockpit. In addition to wanting modifications to the system, the NTSB recommended that operators of the Bell 407 and the MD 600 be temporarily prohibited from operating at altitudes and airspeeds under which a safe autorotation landing is not probable.