When reading AAIB Bulletin S/1 2018 a few things catch my attention:
1). According to the bulletin the general wind direction was north-westerly with a strength of 10 to 12 kt at the surface and around 25 to 30 kt at 1000 ft.
2). The helicopter began a climb on a rearward flight path while maintaining a northerly heading.
3). The climb then paused. (somewhere above 320 ft)
4). Then the helicopter entered an increasing right yaw contrary to the pilot’s left pedal command
6). The helicopter reached a radio height of approximately 430 ft before descending with a high rotation rate.
— The climb out procedure was performed in downwind, (the heading was northerly, but the climb was rearward) so maybe the helicopter was following the same airmass with zero TAS so to speak?.. Somewhere above 320 ft the climb paused. Why?.. Did the helicopter reach a condition that sometimes is referred as ”settling with power” / climb in its own downwash? No descend was reported… If so, did the pilot manage to escape the situation with an unusual procedure by applying max power/max collective?-- The helicopter entered an increasing right yaw and reached 430 ft radio height before going down with high collective and power applied?