I stumbled across this report of the loss of a Bell 47G2, VH-KHL, at Moorabbin in Australia back in 1989, and it reminded me of the R22 accident being discussed in this thread:
https://www.atsb.gov.au/publications.../aair198901526
Another trial instructional flight. Helicopter was placed in a hover and passenger was invited to attempt to control the helicopter by use of the anti-torque pedals and the cyclic control. The passenger overcontrolled the aircraft and pilot (who wasn't rated as an instructor) wasn't able to recover control in time. Both pilot and passenger were seriously injured according to the report. Hope they both fully recovered.