Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Fokker Model F28 Mark 0100 series airplanes. This proposal would require repetitive inspections of certain flanges and finger strips at rib 5.0 of the vertical stabilizer to detect fatigue cracking, and repairs, if necessary. It also would require modifications that would strengthen the torsion box at rib 5.0 and prevent fatigue cracking; one of these modifications would be terminating action for the repetitive inspections. This proposal is prompted by reports indicating that, during full-scale fatigue testing, cracking has been found on the vertical stabilizer of the test article. The actions specified by the proposed AD are intended to detect and prevent fatigue cracking in the subject area, which, if not corrected, could reduce the structural integrity of the vertical stabilizer.