Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Jetstream Model 4101 series airplanes. This proposal would require modification of the existing diaphragms on the surround structure of the Type II emergency exit. This proposal is prompted by a report that, during fatigue tests on a Model 4101 test article, cracking was found in the surround structure of a Type II emergency exit due to fatigue-related stress. The actions specified by the proposed AD are intended to prevent fatigue-related cracking in the surround structure of the Type II emergency exit, which could result in reduced structural integrity of the fuselage pressure vessel.