COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Enstrom F-28 Series Helicopters AD/ENST 28/30 Amdt 2 Tail Rotor Spindle 3/93 Applicability: All F-28F, 280F or 280FX model helicopters and any F-28C, F-28C-2, or 280C models that have been converted to use the 28-150064-11 or -13 spindle. Requirement: Action in accordance with Enstrom Service Directive Bulletin No 0077 Revision B. Compliance: As specified in the requirement document but with a revised effective date of 26 March 1992. Background: This amendment raised in sequence to add the -13 spindle to the AD requirements and to place a service life limit of 1200 hours on the 28-150064-11 and -13 spindles.