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 369/77 Main and Tail Rotor Control Tubes 9/89 DM Applicability: All model 369 series helicopters. Requirement: Action in accordance with McDonnell Douglas SIN No HN-217, DN-158, EN-48 or FN-36, as applicable. Compliance: Part 1 of Requirement Document: Unless already accomplished, within 25 flight hours from 14 July 1989. Part 2 of Requirement Document: At next inspection for issue of a Maintenance Release but not later than 31 December 1989. Background: The manufacturer advises that cracking of the main and tail rotor control tubes, mounted in the vertical tunnel, has been discovered.