In this video it seems that he was in the air when the flap occurred? The only instances of blade flap that I am aware of occur while the gyro is on the ground.
What I don't understand how does one get the blades to flap if you are flying. I have only been aware of blade flap occurring on the ground, mostly in the transition from pre-rotation to take-off when the pilot accelerates to fast and doesn't allow the rotor rpm to match the airspeed, but once the rrpm is over a critical amount then blade flap can't occur.
So if the gyro has lifted off doesn't that mean that the rotors are spinning fast enough that blade flap cannot occur? Would you not have to do unload the rotor somehow first reduce the rrpm below the critical rrpm first then load it back up abruptly to induce flap while flying? Like a rapid forward stick movement to induce low Gs on top of a zoom climb then rapid pull back on the stick after the rotors slowed down below the critical rrpm.
As far as critical angle of attack is concerned I would think one of the challenges with a rotor that the angle attack of the rotor does not necessary give any visual cues to the pilot. In other words unlike a fixed wing the pitch of the fuselage is not necessarily a direct correlation thats reflects the angle of attack of the wing, its variable. In a fixed wing the fuselage will always pitch up exactly the same amount each time according to the angle of attack of the wing and therefore the pilot gets both a visual cue and instrument cue (airspeed indicator) about how much angle of attack is being applied by the position of the stick, what is seen out of the windscreen, and what the ASI is showing, in a gyro the pilot only has the position of the stick to determine how much angle of attack they are applying.
So rather than focus on angle of attack (after all gyro cant stall) the pilot should focus on rotor rrpm in relation to the stick position.