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/56 Amdt 3 Elevator Control System Bob Weight Installation - Inspection and Modification 3/82 Applicability: Models 500, 500A, 500B, 500S, 500U, 520, 560, 560A, 560E, 560F, 680, 680E, 680F, 680F(P) and 720, S/Nos. 1 to 3323 except those aircraft which have complied with Rockwell International Service Bulletins No. 129 Rev. 4 and No. 136 Rev. 3 dated 26 January 1981 as applicable. Document: Gulfstream American Service Information No. SI-176. Note: Rockwell International SB 179 and FAA AD 75-12-09 Amendment 39-4246 refer. Compliance: 1. Unless already accomplished, initially inspect within the next 25 hours' time in service after 8 February 1982, and thereafter at intervals not exceeding 60 hours time in service until modified. 2. Modify within 500 hours' time in service after 8 February, 1982. Note: Aircraft certified to comply with AD/AC/56B and AD/AC/58B are deemed to comply with this Directive. Background: Cracks have been found in the bob weight side supports of six overseas registered aeroplanes. Effectivity has been extended by aircraft serial number and the requirements of AD/AC/56B and AD/AC/58B have been consolidated into this AD.