Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to BHTC Model 206L-4 helicopters. This proposal would require replacing certain hydraulic relief valves (valves) with airworthy valves. This proposal is prompted by a pilot's report of intermittent hydraulic pressure in the flight controls that was caused by a defective hydraulic relief valve. The actions specified by the proposed AD are intended to prevent intermittent hydraulic pressure to the flight controls and subsequent loss of control of the helicopter.