COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Pilatus Britten-Norman BN-2 Series Aeroplanes AD/BN-2/31 Amdt 1 Engine Mounting Frames - Inspection 5/74 Applicability: All models with engine mounting frames P/Nos. NB-20-G- 1901, NB-20-G-5231, NB-51-H-1021 and NB-20-D-5209. Document: Britten Norman SB BN-2/SB.72. Compliance: Unless already accomplished, within 10 hours time in service after 31 May 1974.