COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES DH114 (Heron) Series Aeroplanes AD/DH114/13 Amdt 6 Applicability: All models. Centre Section and Wing Spar Boom - Fatigue Life Limitations 12/89 Requirement: Retire from service the centre section and wing lower spar booms. Compliance: 1. Series 1 aircraft (a) Before Modification 492 and 520 - at or before 4700 hours total time in service. (b) Centre Section lower spar booms - after Modification 492 - at or before 40,000 hours total time in service. (c) Wing lower spar booms - after Modification 520 - at or before 20,000 hours total time in service. 2. Series 2 aircraft (All Series 2 irrespective of power plant) (a) Before Modification 492 and 520 - at or before 3500 hours total time in service. (b) After Modification 492 and 520 - at or before the total time in service as detailed in the following graph. Interpolation between the lines for different average flight times is permissible. Note 1: The total time in service detailed above for the wing spar boom includes any flying hours prior to the embodiment of Modification 520. Note 2: The Authority must be notified of any aircraft operating regularly on stages shorter than 1/2 hour duration so that an appropriate retirement life can be determined. Note 3: Series 2 aircraft fitted with wing external strap modification to STC SA3125WE are exempted from wing lower spar boom retirement. Note 4: The manufacturer has advised that the wing life cannot be extended beyond the life of the centre section spar boom, i.e. a maximum of 30000 hours for Series 2 aircraft. COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Background: These life limitations were established in consultation with the aircraft manufacturer, and taking into consideration Australian operating conditions and in-flight fatigue loads measurements. This Amendment follows a query received by the Authority and extends the graph to cover higher average cruise weights. The lives at lower weights remain unchanged.