COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Schweizer (Hughes) 269 Series Helicopters AD/HU 269/39 Amdt 1 Engine Exhaust System - Inspection 2/72 Applicability: Models 269A with S/Nos. 0011 to 0314, 269A-1 with S/Nos. 0004 to 0041, 269B with S/Nos. 0001 and subsequent, 269C with S/Nos. 0001 and subsequent equipped with 269A4201 or 269A4869 exhaust cabin heater installation. Document: Hughes SIN No. N-88.1. Compliance: Within 50 hours time in service after 29 October 1971 and thereafter at intervals not exceeding 100 hours time in service.