COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES DH114 (Heron) Series Aeroplanes AD/DH114/42 Nose Gear Inner Casing - Inspection NK and Replacement Applicability: All models. Document: Hawker Siddeley TNS Heron (114) No. U.17. Compliance: Inspect casing in accordance with para. 3 of TNS No. U.17 within 50 hours time in service after 31 December 1973 and thereafter at intervals not exceeding 600 hours time in service and after any reported heavy landings.