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FAA requires mode annunciator for fly-by-wire 525

Bell Helicopter’s 525 super-twin will be required to operate with a system that annunciates to the flight crew whether the fly-by-wire system’s flight envelope protections are on or off and other details, the US Federal Aviation Administration says.

The new requirement to be published by the FAA on 7 December in the Federal Register reflects the 525 Relentless’ status as the first civil helicopter to enter service featuring a fly-by-wire control system.

The FAA’s Part 29 regulations governing helicopter design don’t yet have standards specifying how to alert the flight crew about which control modes are engaged.

In the absence of a formal rule, the FAA publishes a special condition that Bell is required to meet in order to obtain a type certificate for the 525, which can accommodate 16-20 passengers.

The special condition will require “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”, according to the notice in the Federal Register.

Bell plans to receive a type certificate for the 525 in 2018 after a one-year delay caused by the investigation into a fatal crash in July 2016. The helicopter broke apart in mid-air after the rotors contacted the tail boom and nose the aircraft, killing both test pilots.