Airworthiness Directives; Saab Model SAAB 2000 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Saab Model SAAB 2000 series airplanes, that requires replacement of the existing fire, tailpipe, and bleed-air overheat detector control units with new, improved units. This amendment is prompted by reports indicating that false engine and auxiliary power unit (APU) fire warnings were issued from the fire detector control units due to moisture or induced voltages of the detector control unit. The actions specified by this AD are intended to prevent such false fire warnings, which could result in unnecessary diversion of the airplane, and resultant increased risks to the airplane, passengers, and crew, and the potential for an overweight landing.