COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Piper PA-24 (Comanche) Series Aeroplanes AD/PA-24/40 Aileron Nose Rib - Inspection and Modification 3/80 Applicability: All models: PA-24-180 and 250 with S/Nos. 24-1 and up, PA-24-260 with S/Nos. 24-4000 and up, and PA-24-400 with S/Nos. 26-1 and up. Document: 1. Piper SL No. 850; or 2. FAA AD 79-20-10, Amdt. 39-3579. Compliance: Inspect within 100 hours time in service after 30 November 1979 and thereafter at intervals not exceeding 100 hours time in service until modified by fitting Piper Kit Part No. 763 893. Background: The manufacturer has received reports of cracks developing in the aileron nose rib of several aeroplanes regardless of any previous modification kit fitted.