COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters AD/HU 369/99 Four-Bladed Tail Rotor Fork 8/99 DM Applicability: Model 369D and E helicopters, with four-bladed tail rotor fork assemblies, part numbers 369D21701-21, installed. Requirement: Inspect in accordance with MD Helicopters Inc. Service Bulletin 369D-198 or 369E- 092, as applicable. Note: FAA Priority Letter AD 99-13-09 refers. Compliance: Unless the initial inspection is already accomplished, before further flight after 30 June 1999; and if affected, thereafter at intervals not to exceed 50 hours time in service. If no ridges are found on the initial inspection, raise an MDR quoting this directive, and include action under para 1E of the requirement document if necessary. This Airworthiness Directive becomes effective on 30 June 1999. Background: The FAA received reports from the manufacturer of the discovery of a discrepant part. During the manufacturing process, an unknown number of certain four-bladed tail rotor fork assemblies were incorrectly machined in critical areas after the shot-peening process. The two ridges on each of the arms of the fork assemblies were incorrectly machined off. This condition, if not corrected, could result in failure which could cause loss of a tail rotor blade and subsequent loss of control of the helicopter.