Airworthiness Directives; Fokker Model F28 Mark 0100 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Fokker Model F28 Mark 0100 series airplanes, that requires repetitive inspections of certain flanges and finger strips at rib 5.0 of the vertical stabilizer to detect fatigue cracking, and repairs, if necessary. This amendment also requires modifications that would strengthen the torsion box at rib 5.0 and prevent fatigue cracking; one of these modifications constitutes terminating action for the repetitive inspections. This amendment 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 this 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.