COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 747 Series Aeroplanes AD/B747/145 Amdt 1 Outboard Engine Strut Spring Beam 1/99 Applicability: Model 747 series aircraft, line numbers 202 through 396, equipped with Pratt & Whitney Model JT9D-70 engines. Requirement: Action in accordance with the technical requirements of FAA AD 98-21-17 Amdt 39- 10826. Note: Boeing Service Bulletins 747-54A2171 and 747-54-2177 refer. Compliance: As specified in the Requirement Document with a revised effective date of 28 January 1999. This Amendment becomes effective on 28 January 1999. Background: A failure of an outboard spring beam on a number 4 engine strut was reported. The failure was due to a material problem in the titanium spring beam which is only fitted to B747 aircraft with JT9D-70 engines. Continued operation with a damaged spring beam could result in loss of an engine. Amendment 1 is issued in response to a new FAA AD which was prompted by the development of an improved process for manufacturing titanium spring beams that will eliminate the embedded porosity flaws in the existing spring beams, from which fatigue cracking can originate. The original issue of this Airworthiness Directive became effective on 25 June 1995.