FAA 2019-10-51

This emergency AD was prompted by reports of fatigue cracks in the fuselage frame, through the left-hand door frame webs and frame cap at station 4135. These cracks occurred on certain serial numbered helicopters with STC SR00592DE installed. The cracks initiated under the doubler that reinforces the door frame where recessed medical wall fittings are attached. In one case, the crack under the doubler propagated through the inboard frame cap and onto the inboard web. This condition, if not corrected, could result in excessive vibration, an in-flight breakup, and subsequent loss of control of the helicopter. Although the exact cause of this unsafe condition is still being investigated, the FAA has determined that the cracks are a result of the recessed medical wall rack installation