Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
This Airworthiness Directive (AD) is prompted due to the discovery of cracks in the upper wing strut fittings of some PC-6 aircraft.
It is possible that the spherical bearing of the wing strut fittings installed in the underwing can be loose in the fitting or cannot rotate because of corrosion. In this condition, the joint cannot function as designed and fatigue cracks may then develop. Undetected cracks in this area could lead to failure of upper attachment fitting. This could result in the failure of the wing structure with subsequent loss of control of the airplane.
The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.