Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Fokker Model F27 Mark 100, 200, 300, 400, 500, 600, and 700 series airplanes. This proposal would require repetitive x-ray inspections to detect cracks in stringers 4 through 7 of the lower skin of the wings, and modification or repair, if necessary. The proposed AD also would require modification of the stringers of the lower skin of the wings, which would terminate the repetitive inspections. This proposal is prompted by reports of fatigue cracking found in stringers 4 through 7 of the lower skin of the wings. The actions specified by the proposed AD are intended to prevent such fatigue cracking, which could result in reduced structural integrity of the wings.