AIRWORTHINESS DIRECTIVE For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/ROTAX/20 and issues the following 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. Rotax Piston Engines AD/ROTAX/20 Amdt 1 Exhaust Muffler Inspection 12/2004 Applicability: a. Rotax 914 F series aircraft engines with serial numbers (S/N) 4,420.373, 4,420.374, 4,420.376, and 4,420.378 up to 4,420.391 inclusive, and 4,420.393, 4,420.394, 4,420.396, 4,420.397 and 4,420.399 up to 4,420.406 inclusive, with exhaust muffler part number (P/N) 979402 installed. b. Rotax 914 F series engines from S/N 4,420.407 onwards with exhaust muffler P/N 979402 or P/N 979404 installed. c. Exhaust muffler P/N 979402 with S/N 02.0001 up to S/N 02.0322 inclusive and S/N 03.0001 up to 03.0108 inclusive. d. Exhaust muffler P/N 979404 from 03.0200 onwards. Requirement: 1. Visually inspect the exhaust muffler exterior for smoke traces or cracks in accordance with Rotax mandatory Service Bulletin (SB) SB-914-028 dated March 2004 or later revision as approved by Austrian ACG or EASA. 2. Replace any exhaust muffler that is found to have smoke traces or cracks, with an exhaust muffler that is serviceable and not affected by provisions of this directive. Note 1: Airworthiness Directive A-2004-005 R1 published by Austrian ACG and approved by EASA under reference no 2004-10151 dated 5th October 2004 refers. Compliance: 1. Unless previously accomplished, with-in 50 hours time-in-service after the effective date of this directive, and thereafter every 50 flight hours. 2. Before further flight. Note 2: Installation of an exhaust muffler that is approved by the manufacturer and is not affected by the provisions of this directive is considered terminating action to the requirements of this AD. This Amendment becomes effective on 25 November 2004. Rotax Piston Engines AD/ROTAX/20 Amdt 1 (continued) Background: The initial issue of this directive addressed the unsafe condition caused by the occurrences of cracks in the area of exhaust muffler bottom and exhaust flange. The leaking hot exhaust gases can cause fire. This amendment addresses the same unsafe condition but with the expanded applicability list. This amendment also mandates repetitive inspection at regular intervals. The original issue of this directive became effective on 27 November 2003. James Coyne Delegate of the Civil Aviation Safety Authority 14 October 2004 The above AD is notified in the Commonwealth of Australia Gazette on 3 November 2004.