COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Twin Commander (Gulfstream/Rockwell/ Aerocommander 500, 600 and 700) Series Aeroplanes AD/AC/90 Wing Station 39 Wing Ribs 5/95 Applicability: Models 690, 690A, and 690B S/n 11001 to 11566 and Model 685 S/n 12001 to 12066. Requirement: Modify the wing ribs at WS 39 in accordance with Twin Commander Service Bulletin 211 Rev 1 Part II. Compliance: Within 50 hours' time in service after 25 May 1995, or at the next inspection for Maintenance Release issue after 25 May 1995, whichever occurs first. Background: This Directive is issued to prevent an under-strength condition developing in the wing ribs at WS 39, and is part of the requirements of FAA AD 94-04-12. This Directive will be amended to include the spar cap and stringer inspections of FAA AD 94-04-12, if subsequent information is received indicating that this is necessary.