Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Saab Model SAAB 2000 series airplanes. This proposal would require replacement of the existing fire, tailpipe, and bleed-air overheat detector control units with new, improved units. This proposal 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 the proposed 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.