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 39.1 (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. Boeing 737 Series Aeroplanes AD/B737/234 Pylon Sealing 1/2005 Applicability: Model 737-600, -700, -700C, -800, and -900 series aeroplanes, line numbers 1 through 946 inclusive. Requirement: 1. Perform a general visual inspection for sealant at the interface of the diagonal brace fitting and the aft bulkhead and at the four bolts common to the interface, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1039, Revision 1, dated 10 October 2002. (a) If the findings of the general visual inspection are as described in paragraphs (1)(a)(i) and (1)(a)(ii) of this Directive, then no further action is required by this Directive. (i) The seal is continuous or there is evidence of fay seal squeeze out present. (ii) The bolts have evidence of sealant squeeze out or a cap seal exists. Application of Fillet Seal (b) The seal is not continuous and there is no evidence of fay seal squeeze out present, fillet seal around the interface of the diagonal brace fitting and the aft bulkhead, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1039 Revision 1. Application of Cap Seal (c) If the bolts do not have evidence of sealant squeeze out and no cap seal exists, cap seal the four bolts common to the interface, in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54- 1039, Revision 1. Note: FAA AD 2004-22-27 Amdt 39-13855 refers. Compliance: For Requirement 1: Unless previously accomplished, within 18 months or 3,500 flight cycles after the effective date of this Directive, whichever occurs first: For Requirement 1(b) and 1(c): Before further flight. Boeing 737 Series Aeroplanes AD/B737/234 (continued) This Airworthiness Directive becomes effective on 20 January 2005. Background: This Directive requires a general visual inspection for sealant at the interface between the diagonal brace fitting and the aft bulkhead and at the four bolts common to the interface. It also requires applying sealant if none is present or if it is not continuous. This action is necessary to prevent flammable fluid in the upper or rear pylon areas from leaking past unsealed areas and onto a hot engine nozzle, which could result in ignition of the fluid, causing an undetected and uncontrollable fire to spread into the engine struts. This action is intended to address the identified unsafe condition. James Coyne Delegate of the Civil Aviation Safety Authority 1 December 2004 The above AD is notified in the Commonwealth of Australia Gazette on 22 December 2004.