The ATSB reports that: "... the pilot was undergoing training for mustering approval by a supervising pilot, and, after completing about 7 hours of mustering, the helicopter was returning to a location near Dingo, when about 1,000ft above ground level (AGL) the supervising pilot instructed the pilot to conduct a practice autorotation turning through 180°, which the pilot completed, increasing power when at about 5ft AGL."
"During the subsequent climb, when at about 450ft AGL, the supervising pilot took control of the helicopter and initiated a second autorotation. The supervising pilot initially observed the airspeed at about 65kt, the rotor rpm in the green arc and the autorotation ‘looking good’, and assumed at this stage that he had handed control of the helicopter to the other pilot. At about 100ft AGL, the pilot detected the rotor rpm decaying and a rapid rate of descent, but still assumed that the supervising pilot had control of the helicopter. When at about 20-40ft AGL, the supervising pilot observed the vertical speed increasing and the rotor rpm decreasing and rapidly lowered the collective and increased the throttle. Just prior to the helicopter contacting the ground, the supervising pilot flared then levelled the helicopter and raised the collective."
|Photo source: ATSB|
The helicopter landed hard, bounced once and rotated through about 180° before coming to rest. The pilot sustained serious injuries and the supervising pilot minor injuries. The helicopter was substantially damaged. The ATSB report concludes by stating that: "This incident highlights the importance of good communication between a flight instructor and their student and the use of handover/takeover techniques to clarify who has control of the aircraft at any time."
Referring CQ Plane Spotting Blog post - http://cqplanespotting.blogspot.com.au/2014/08/investigation-in-crash-of-stock-air.html