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-23/81 Fuselage - Step Attachment Area - Inspection 9/80 Applicability: All models PA-23 & PA-23-160 with S/Nos. 23-1 to 23-2046; All models PA-23-235 with S/Nos. 27-505 to 27-622; All models PA-23-250 with S/Nos. 27-1 to 27-504; All models PA-23-250 (6 place) with S/Nos. 27-2000 and subsequent. Document: Piper SB No. 672. Compliance: Within 100 hours time in service after 30 September 1980 and thereafter at intervals not exceeding 100 hours time in service. Background: The manufacturer has received reports which indicate that some aeroplanes may develop cracks in the fuselage tubular cross member adjacent to the cabin entry step attachment.