AAIB investigation to Bell 429 GlobalRanger, G-WLTS
Un-commanded yaw during Power Assurance Check, Melksham Airbase, Wiltshire, 2 January 2019.
Summary:
The report considers two events which occurred while the pilot was conducting a Power Assurance Check. In one, an un-commanded yaw pedal movement caused a rapid rotation of the helicopter through two and a half complete rotations; in the other, a trim runaway was contained by the pilot. The trim runaway was found to be an unknown feature of the Automatic Flight Control System logic.
Following these events, safety action was taken by the helicopter manufacturer and Transport Canada to help crews respond to a yaw trim runaway and to address the underlying causal factor. Also, the flight recorder manufacturer improved the way it reported the results of CVR recording inspections.
Two Safety Recommendations are made: one to Transport Canada in relation to conduct of the Power Assurance Check; and one to the European Union Aviation Safety Agency to ensure that the installation of new equipment on aircraft does not have a detrimental effect on existing equipment.
Download report:
Safety Recommendation document: