Summary
We propose to adopt a new airworthiness directive (AD) for certain Pilatus Aircraft Ltd. (Pilatus) Model PC-7 airplanes. This proposed AD would require you to do repetitive eddy-current, non- destructive inspections of the nose skin and adjacent structure above the left and right main landing gear bay and repetitive visual inspections of the forward support structure of the floor panel for crack damage. If you find any crack damage, this proposed AD would require you to contact Pilatus to obtain a repair solution and incorporate the repair. This proposed AD results from mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. We are proposing this AD to detect and correct cracks in the nose skin and adjacent structure above the left and right main landing gear bay and in the forward support structure of the floor panel. Crack propagation in certain areas could lead to failure of the main wing torsion box, which could result in loss of control.