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. This amendment requires replacement of the ignition exciter in the auxiliary power unit (APU) with a part that is designed to operate better in cold weather. This amendment is prompted by two occurrences of the APU failing to start after flight in cold soak conditions. The actions specified by this AD are intended to prevent such APU failure, which could result in the inability of the APU to restart the engines in the event both engines quit operating during flight.