Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Bell Helicopter Textron Canada (BHTC) Model 407 helicopters. This proposal would require replacing a certain hydraulic relief valve (valve) with a different valve. This proposal is prompted by the discovery of a manufacturing defect in a valve. The actions specified by the proposed AD are intended to prevent intermittent loss of hydraulic pressure to the flight controls and subsequent loss of control of the helicopter.