COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Robinson R22 Series Helicopters AD/R22/47 Fuel Tank Vent System 13/98 DM Applicability: R22 helicopters S/Nos. 0002 through 1451 except aircraft overhauled by Robinson after January 1991. Requirement: Inspect, and modify if required, the fuel tank vent system in accordance with Robinson R22 Service Bulletin No. 84. Note 1: FAA Priority Letter AD 98-21-09 also refers. Note 2: Robinson Service Bulletin No. 83 also addresses fuel tank vent system modification. Compliance: Within 25 hours time in service, or 30 days, from the effective date of this Directive, whichever occurs first. This Airworthiness Directive becomes effective on 14 October 1998 Background: This directive is prompted by reports of uncommanded loss of engine power on R22 helicopters. The power loss events have been attributed to kinking of the fuel tank vent system.