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 replacing the radio tuning units (RTU's) and associated components with new, improved parts. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent NAV/COM radios from simultaneously changing tuned frequencies and transponder codes due to a black screen failure or ``blanking'' of an RTU, which could result in loss of communications capability and air traffic control data.