COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Boeing 737 Series Aeroplanes AD/B737/106 Aileron Centring Spring and Trim Mechanism 6/97 Applicability: Model 737 series aircraft; as listed in Boeing Service Bulletin 737-27-1155, dated October 26, 1989; as revised by Notices of Status Change No. 737-27-1155NSC1, dated January 25, 1990, No. 737-27-1155NSC2, dated February 15, 1990, and No. 737-27-1155NSC3, dated May 17, 1990. Requirement: Action in accordance with the technical requirements of FAA AD 97-04-01 Amdt 39- 9925. Compliance: Before 21 September 1998. This Airworthiness Directive becomes effective on 22 May 1997. Background: This Directive is prompted as a result of findings by the Critical Design Review team of the design of the flight control systems on Model 737 series aircraft. The actions specified by this Directive are intended to prevent jamming of the aileron control system during flight due to fracturing of the springs in the aileron centring units.