thanks for all replies and sorry for not participate into discussion (a bit busy lately)
here is another example of risky maneuver (in my opinion) , as long as airflow is from underside of the rotor it's fine , but when you raise up collective so dynamically doing kind of flare , your blades will change AoA , load will increase and if your engine is not powerfull enough is there a risk of blade(rotor) stall ?
https://www.instagram.com/reel/CqRni...d=MDJmNzVkMjY=