Originally Posted by
212man
How do we know that it was?
212Man from AAIB Special Bulletin:
The helicopter then began a climb on a rearward flight path2 while maintaining a northerly heading.
Gear retraction started as it passed through a height of approximately 320 ft. The climb then paused. Heading changes consistent with the direction of pedal movements were recorded initially, then the helicopter entered an increasing right yaw contrary to the pilot’s left pedal command. The helicopter reached a radio height3 of approximately 430 ft before descending with a high rotation rate.