Airworthiness Directives; Fokker Model F27 Mark 500 Airplanes

The FAA is adopting a new airworthiness directive (AD) for all Fokker Model F27 Mark 500 airplanes. This AD requires an inspection to determine whether certain main landing gear (MLG) drag stay units (DSUs) are installed. This AD also requires an ultrasonic inspection to determine if certain tubes are installed in the affected DSUs of the MLG, and related investigative/corrective actions if necessary. This AD results from a report that, due to fatigue cracking from an improperly machined radius of the inner tube, a drag stay broke, and, consequently, led to the collapse of the MLG during landing. We are issuing this AD to prevent such fatigue cracking, which could result in reduced structural integrity or collapse of the MLG.