Lonewolf 50
The engine start sequence allows you to move the FFCL to an idle position and at that point the Ng is about 70% and the blades are turning. Once you are all squared away, radios humming,Navaids up, everyone board belted and doors secured etc. you move the lever to the flight gate. At this point, the rotor is considered to be at "full" flight RPM and in governed mode.In other words, you can pull pitch and fly.
To leave it unattended,one would consider leaving it at ground idle,frictions tightened down on the cyclic and the collective locked. The collective in the AS350 has a propensity to pop up.There is ,therefore, a down lock mechanism.Every time you lower the collective fully with the intention of shutting down or spending some time on ground, it is required that you positively lock the collective.
The AS350 has no stick trim mechanism and hence the only safeguards against such incidents are the collective lock and cyclic friction which are considered inadequate protection. So, most companies that I know of who operate the type, require that the pilot not leave the aircraft unattended,even at ground idle.Now ,I don't know what goes on in the bush.You may have to ask Bordeux Bob about that.
I have a sneaky suspicion that the collective ,in this case, may not have been positively locked down and popped up on the pilot while he was out.But, that is for the NTSB to find out.
Bottom line, young uns, if you are newly minted on the AS350 disregard folks like Bordeaux Bob's advice and stay inside the machine , if you intend to let it run.If you need to get out, shut her down. Five minutes is not a big loss of time ,especially when you consider the alternative of eternity.
Alt3.