COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Airtractor AT-300, 400 and 500 Series Aeroplanes AD/AT/3 Amdt 5 Landing Gear 4/97 Applicability: All models fitted with main landing gear spring legs P/N 40007-2/-3, 40058-1/-2 and 40086-1. Requirement: Retire the main landing gear spring legs, the forward and aft main gear clamp block bolts and the inboard main gear large bolt. Note: Snow Engineering Service Letters #117, #119 and FAA AD 82-06-12 refer. Compliance: Retire the main landing gear spring legs at the number of landings listed in Table 1. At the same time, retire the forward and aft main gear clamp block bolts and the inboard main gear large bolt. If, during initial compliance with this directive, any or all of the components listed in the above Requirement are found to be outside the Table 1 lives, replace those components within 500 landings after 27 March 1997, or by 30 June 1997, whichever occurs first. Table 1 - Spring Retirement Lives Spring Part # Thickness (in) Aircraft Fitted Retire at every (#LDGs) 40007-2 1.0 AT-300, -301 7500 40007-2 1.0 AT-302, -400A 6000 40058-1 1.0 AT-300, -301 7500 40058-1 1.0 AT-400, -400A 6000 40058-2 1.19 AT-400, -402, -402A, -402B 10000 40058-2 1.19 AT-301, -400A, -401, -401B 12500 40007-3 1.12 AT-301, -401, -401B 12500 40086-1 1.31 AT-501, -502, -502A, -502B, -503A 8000 Where the total number of landings during a period of service has not been recorded, the number of landings for that period of service is to be calculated using a rate of 4 landings per hour time in service. This Amendment becomes effective on 27 March 1997. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Background: The original directive was written to inspect for cracking of the undercarriage springs and to publish a life limitation on the springs after a number of failures. Since initial issue of the directive and subsequent amendments, service history and the introduction of a bolt retirement life have led to a need to reassess the directive. This amendment deletes the retirement life based on flight hours, as the cause of failure is driven by number of landings. Amendment 4 of this Airworthiness Directive became effective on 30 January 1997. Amendment 3 of this Airworthiness Directive became effective on 17 August 1995. The original issue of this Airworthiness Directive became effective on 30 September 1982.