COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bell UH-1 Series Helicopters AD/UH-1/1 Tail Rotor Blades 9/96 DM Applicability: All models fitted with tail rotor blades P/N 204-011-702-015 or -121 with serial numbers A-20262 to A-20268, A-20270 to A-20282, A-20284 to A-20287, A-20289 to A-20422, A-20424 to A-20428, A-20430 to A-20433, A-20435 to A-20464, A- 20466 to A-20497, A-20499 to A21019, A-21027 to A-21031, A-21041, A-21047, A- 21049, and A-21059 Requirement: 1. Clean the tail rotor (TR) blades using a mild detergent and water to remove soot and grime; and then visually inspect each TR blade for peeling, flaking, or bubbling paint, or visible corrosion along the bond lines, viewed from the root and tip ends of each blade, and at the abrasion strip bond line on both faces of the blade from the root to the tip. 2. If peeling, flaking, or bubbling paint is found remove the paint from the area and inspect for corrosion. If no corrosion is found refinish blade and return to service. 3. Remove from service any blade where corrosion is found. Replacement with blades not listed in the Applicability terminates this Directive. Note 1: FAA AD 96-12-26 refers. Note 2: BHTI ASB 204-96-48 Rev A refers. Compliance: Within 10 hours time in service after 26 June 1996, thereafter at intervals not exceeding seven days. Background: The manufacturer has reported that certain serial number tail rotor blades were manufactured with internal leading edge doublers fabricated from clad aluminium material instead of bare aluminium material. The bond strength of clad aluminium material declines rapidly with exposure to normal environmental conditions. The condition, if not corrected could lead to debonding of the main spar leading edge doubler which in turn could cause failure of the TR blade and subsequent loss of control of the helicopter.