Airworthiness Directives; Bell Helicopter Textron Inc. Helicopters

We are adopting a new airworthiness directive (AD) for Bell Helicopter Textron Inc. (Bell) Model 412 and 412EP helicopters with certain static inverters (inverters) installed. This AD requires revising the Rotorcraft Flight Manual (RFM) and installing a placard in full view of the pilot to limit flight to visual flight rules (VFR) only and prohibit night operations. This AD is prompted by failures of certain inverters, most of which resulted in smoke in the cockpit. The actions specified by this AD are intended to restrict flight to VFR only and prohibit night operations to allow safe operation in the event of failure of an affected inverter. This failure would increase pilot workload during instrument flight rules (IFR) and could result in loss of certain pilot information displays and subsequent loss of control of the helicopter.