Incident Overview
A helicopter was conducting a hover-taxi check as part of a post-maintenance flight test when the pilot initiated a right turn. During the maneuver, the helicopter began to roll to the right without any command from the pilot. Despite applying left cyclic input, the pilot was unable to stop or reverse the uncommanded roll.
Sequence of Events
The right roll continued unchecked, and the main rotor blades struck the ground. Subsequently, the helicopter impacted the ground in a nose-down, right-bank attitude. The pilot had been performing the hover-taxi check as a standard procedure following maintenance work on the aircraft.
Examination Findings
Investigators examined the helicopter, focusing on the hydraulic dampers connected to the stabilizer bar assembly. Testing revealed that these dampers were not adjusted adequately. This improper adjustment resulted in little to no response from the cyclic control system when the pilot attempted to correct the roll. The inadequate damping prevented the stabilizer bar from functioning as intended, which compromised the helicopter's control characteristics during the hover-taxi maneuver.