COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes
AD/CESSNA 170/16
Amdt 1
Rear Spar 11/67
Applicability: All models prior to models M and F172M.
Requirement: 1. Visually inspect the main plane rear spar web at the root attachment area and the upper flange of the rear channel, at the outer end of the attachment fitting, for fatigue cracks.
2. These cracks originate in the radius which is located beneath the attachment fittings.
3. 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.
4. 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: At intervals not exceeding 100 hours time in service.