COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES SAAB SF340 Series Aeroplanes AD/SF340/21 Auto-Coarsening 2/91 DM Applicability: All SAAB SF340 Series aircraft S/No 004 through 159 inclusive. Requirement: Action in accordance with the technical requirements of FAA AD 90-21-16 Amdt 39- 6763. Note 1: This directive cancels AD/SF340/13. Note 2: Swedish AD No 1-037 refers and cancels Swedish AD No 1-028. Compliance: Prior to 30 April 1991 Background: As previously incorporated Electrical Control Unit (ECU) modifications may affect single engine climb performance. The FAA, Swedish Airworthiness Authority and the Aircraft Manufacturer requires these modifications to be removed and a modified ECU to be installed.