COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Piaggio P166 Series Aeroplanes AD/P166/5 Engine Nacelle - Drainage Modification NK Applicability: All models. Requirement: Provide adequate drainage facilities for all sections of the lower nacelles. Compliance: Forthwith.