Airworthiness Directives; Bombardier, Inc., Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Bombardier, Inc., Model BD-700-2A12 airplanes. This AD was prompted by a report indicating that the fan in a transformer rectifier unit (TRU) can become inoperative in a manner that is not detectable by the fan monitoring circuit. This AD requires replacement of the existing TRU Number 2 with a new part number that incorporates a correction to the fan and the monitoring circuit. This AD also prohibits the installation of affected parts. The FAA is issuing this AD to address the unsafe condition on these products.