AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 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. Agusta A109 Series Helicopters AD/A109/58 Lower Semichannel Assemblies 9/2007 DM of the Forward Firewall Applicability: Model A109E helicopters, with serial numbers up to and including 11694, except serial numbers 11633 and 11634. Model A109S helicopters, with serial numbers up to and including 22034, except 22026 and 22033. Requirement: Action in accordance with Agusta Alert Technical Bulletin (BT) No. 109EP-79 or BT No. 109S-15, as applicable. Note: EASA Emergency AD 2007-0192-E refers. Compliance: Within 20 flight hours after 18 July 2007, but not later than 30 September 2007; unless already accomplished. This Airworthiness Directive becomes effective on 18 July 2007. Background: Interference between the forward firewall metallic spacer part number 109-0642-01-195 and the main drive shaft part number 109-0415-06-103 has been detected on Model 109LUH helicopters. Damage to the main drive shaft, unless detected and corrected, could result in failure of the drive shaft and consequent loss of controllability. David Villiers Delegate of the Civil Aviation Safety Authority 16 July 2007