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 369/72 Horizontal Stabilizer 2/88 DM Applicability: All model 369E and 369F/FF series helicopters. Requirement: Modify the horizontal stabilizer assembly by removing the existing tab weights and installing stiffeners on the outboard ends of the stabilizer in accordance with McDonnell Douglas Helicopter Company SIN No. EN-40/FN-29. Note: This is intended as a preventive modification only, not as a repair scheme for pre-existing cracks. If such cracks are detected while carrying out the modification they must be separately repaired. Compliance: Within 100 hours time in service after 1 December 1987, or by 1 March 1988, whichever occurs first. Background: The horizontal stabilizer skin and the tabs have been cracking at the outboard ends of the horizontal stabilizer tabs as a result of vibration. Cracking may cause flutter. This modification adds stiffness to the outboard ends of the tabs.