COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 185 Series Aeroplanes AD/CESSNA 185/2 Amdt 4 Rear Spar 12/74 Applicability: All models except those with rear spars P/Nos. 0523400-90 LH and -91 RH; 0523400-111 LH and -112 RH. Requirement: 1. Modify the rear spar root, left and right mainplanes on all agricultural aeroplanes in accordance with Rex Aviation Drawing RA-491 or an alternative scheme approved by the Secretary. 2. Inspect the mainplane rear spar web for fatigue cracks in the root area. These cracks originate in the radius which is located under the attachment fittings. This inspection shall be carried out using a magnifying glass of at least 4X magnification or alternatively a device such as the "Syte Ade" may be employed. 3. Inspect the upper flange of the rear spar channel at the outer end of the attachment fitting. This can be done via the flap bay inner inspection panel. 4. Since the trailing edge root end fits closely to the spar, it may be difficult to detect possible cracks, therefore where doubt exists, the trailing edge root end rib shall be removed for more detailed inspection. Note: The affected area is illustrated in Rex Aviation Technical Memorandum No. 12 dated 10 May 1960. Compliance: For Para 1: Forthwith. For Paras 2 and 3: Aeroplanes modified to Rex Aviation Drawing RA-491 - at intervals not exceeding 500 hours time in service. All other aeroplanes - at intervals not exceeding 100 hours time in service.