COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Eurocopter AS 355 (Twin Ecureuil) Series Helicopters AD/AS 355/23 Hydraulic System 12/86 DM Applicability: All model AS 355 E, F, F1 and F2 helicopters. Requirement: Action in accordance with Aerospatiale AS 355 Service Bulletin No. 29-01. Note: French AD 86-150-30(B) refers. Compliance: Within 300 hours time in service after 30 November 1986 or before 31 January 1987 whichever occurs first. For spares: before installation in an aircraft after 30 November 1986. Background: A spring spacer is fitted to prevent an overpressure in the hydraulic systems if the flange of the regulator valve stem, fitted to the filter unit, should come off.