COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Cessna 206 Series Aeroplanes AD/CESSNA 206/3 Amdt 3 Wing Rear Spar 1/90 Applicability: All models fitted with rear spar assembly P/N 1220050-1, -2, -23, -24, -25 or -26. Note: These part numbers are in aircraft serial numbers 206-0001 to 206-0275, U206-0276 to U206-1367, and P206-0001 to P206-0597; excepting of course those aircraft that have had rear spar assemblies replaced with later part numbers. Requirement: Visually inspect each main plane rear spar web for fatigue cracking at the root attachment area and the upper flange of the rear spar channel at the outer end of the attachment fittings. These cracks originate in the radius which is located beneath the attachment fittings. This inspection shall be carried out using a magnifying glass of at lease 4X magnification or alternatively, a device such as the "Syte Ade" may be employed. Since the trailing edge root end rib 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: Within 500 hours time in service after 25 January 1990, and thereafter at intervals not exceeding 500 hours time in service. Background: There have been several reports of cracks in the rear spar near the attachment fitting, including at least one fatal accident, in another model that uses a similar design of spar assembly. The problem seems to be confined to the early design rear spars. Later spars have a thicker web and additional doublers. Amendment 3 changes the applicability of this Directive to clarify that only the early part number rear spars need to be inspected. The inspection interval has been extended to 500 hours based on service experience.