AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/UH-1/6 Amdt 1 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section. Bell UH-1 Series Helicopters AD/UH-1/6 Amdt 2 Main Rotor Mast and Trunnion 4/2002 DM Applicability: Models UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, and HH-1K, TH- 1F, TH-1L, and Southwest Florida Aviation SW204, SW204HP, SW205, and SW205A-1 helicopters; equipped with main rotor mast, part number 204-011-450- 007, -105, or -109, or main rotor trunnion, part number 204-011-105-001. Requirement: Action in accordance with the technical requirements of FAA AD 2002-01-31 Amdt 39-12628. Compliance: As specified in the Requirement document with a revised effective date of 13 March 2002. This Amendment becomes effective on 13 March 2002. Background: This Directive was raised following several fatigue failures of the mast and a reported head separation from a 205A-1 helicopter. This Directive requires conversion of flight hours to Retirement Index Numbers and an inspection of each main rotor mast for burr or an inadequate radius in the snap ring groove. Amendment 1 was prompted by the discovery of a crack in a main rotor mast with a lower Retirement Index Number value than the established life limit. Certain actions were necessary to preclude the occurrence of a fatigue crack in the damper splined area of a main rotor mast. Amendment 2 is issued in response to a new FAA AD which establishes a retirement life for the main rotor trunnion based on monitoring the number of torque events and flight hours rather than flight hours only as currently required; and also adds a note clarifying that the mast serial number is defined by 5 or fewer digits plus various prefixes. Bell UH-1 Series Helicopters AD/UH-1/6 Amdt 2 (continued) The original issue of this Airworthiness Directive became effective on 28 April 2000. Amendment 1 of this Airworthiness Directive became effective on 15 November 2000. David Alan Villiers Delegate of the Civil Aviation Safety Authority 6 March 2002 The above AD is notified in the Commonwealth of Australia Gazette on 13 March 2002.