Airworthiness Directives; Jetstream Model 4101 Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Jetstream Model 4101 airplanes, that requires modification of the existing diaphragms on the surround structure of the Type II emergency exit. This amendment is prompted by a report indicating that, during fatigue tests on a Model 4101 test article, fatigue-related cracking was found in the surround structure of a Type II emergency exit. The actions specified by this AD are intended to prevent such cracking in the surround structure, which could result in reduced structural integrity of the fuselage pressure vessel.