Bell 525 interior. Image courtesy of Bell Helicopter
The FAA is proposing special conditions for the Bell Helicopter 525 Relentless. As the first commercial fly-by-wire helicopter, the FAA said it believes the model should feature mode annunciation.
“This helicopter will have a novel or unusual design feature associated with fly-by-wire flight control system functions that affect the pilot awareness of the flight control modes while operating the helicopter,” Thursday’s Federal Register stated. “The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These proposed special conditions contain the additional safety standards that the administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.”
For background information, the FAA offered that the 525’s design has a four-axis full authority digital fly-by-wire flight control system that uses pilot input and coupled flight director modes. Believing that currently regulations are inadequate when it comes to pilot awareness of the control modes, the FAA is proposing a special condition that would require that “suitable mode annunciation be provided to the flight crew for events that significantly change the operating mode of the system but do not merit the traditional warnings, cautions and advisories.”
The FAA is welcoming comments on or before Jan. 22, 2018. The rule would affect only the 525, as it is “not a rule of general applicability.”
Bell resumed flight test activity for its 525 in July after receiving an experimental certificate renewal from the FAA. The company said it still hopes to certify its fly-by-wire aircraft next year. The NTSB probe is ongoing, and the board has provided no official update since its July 29, 2016, preliminary report.
Bell told R&WI that this special conditions notice is a “normal part of the certification process and not linked to the NTSB report.”