COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Piper PA-23 (Apache and Aztec) Series Aeroplanes AD/PA-23/18 Aileron Balance Weight Brackets - Reinforcement NK Applicability: Model PA-23 with S/Nos. 23-1 to -731, -733, -734, -735, -737, -738, -742 to -768, -770 to -776, 0778 to 0783, -785, -786, -788 to -793, -795, -796, -798 to -800. Document: 1. Piper SB No. 149; or 2. FAA AD 56-27-3. Compliance: Before issue of a Certificate of Airworthiness.