AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/BELL 407/20 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 Helicopter Textron Canada (BHTC) 407 Series Helicopters AD/BELL 407/20 Amdt 1 Tailboom Tail Rotor Gearbox Support Casting 11/2002 Applicability: Model 407 helicopters, serial numbers 53000 through 53475; equipped with tailboom assemblies part number 407-030-801-105, -107, or 407-530-014-103, identified as serial numbers 53390 through 53440, 53449, BP921, BP1014, and subcomponent tail rotor gearbox support casting part number 406-030-121-105, identified as serial numbers 980867/01-2, -3, -4, -5, -8, -9, -10. Requirement: 1. Determine if the affected part is installed on the applicable aircraft by conducting Part I of Alert Service Bulletin 407-02-53, dated 5 June 2002. 2. If an affected casting is identified by Requirement 1, perform an inspection of the casting for cracks in accordance with Part II of Alert Service Bulletin 407-02-53; and, if a crack is found, replace the tailboom before further flight. 3. Remove the tailboom from service until the affected tail rotor gearbox support casting is replaced. Note: Transport Canada AD CF-2002-32R1 refers. Compliance: 1. Within 10 hours time in service or 7 days after 7 August 2002, whichever occurs first. 2. Before further flight. Thereafter at intervals not to exceed 25 hours time in service. 3. Before 1 October 2002. The compliance times remain unchanged by this issue. This Amendment becomes effective on 31 October 2002. Background: Transport Canada received a report of a cracked tail rotor gearbox support casting that is part of the tailboom assembly. Investigation revealed the crack originated from a weld repair made during fabrication of the part. Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters AD/BELL 407/20 Amdt 1 (Continued) Amendment 1 is issued in response to a revision of the related Transport Canada AD which corrects the issue date of the Requirement document. The original issue of this Airworthiness Directive became effective on 9 October 2002. David Alan Villiers Delegate of the Civil Aviation Safety Authority 12 September 2002 The above AD is notified in the Commonwealth of Australia Gazette on 9 October 2002.