Aerodynamic braking
Aerodynamic braking should always be avoided.
As the rotor slows down the relative impact of wind and wind gusts becomes bigger (v gust stays, v tip decreases) : the perturbation to a rotor is greater because the disturbance forces remain while the rotor gets less stiff.
It should be clear to any one that tried it, that aerodynamic braking of the MR creates extra flapping. Exactly the same principles apply for the TR.
The greater the angle of attack the greater the disturbance, the greater the flapping, the greater the risk of a strike
An extra caution is that: as the system is slowing down the resonance characteristics change (the fase lags in the rotors) so points of max. flap need not be at the same angle as at nominal rotor speed.
Besides the risk of strike, the flapping also (over)loads the system.
The power the TR can give as a brake is further more quite limited as soon as RPM is below say 70%.
If left with no choice I would:
- use maximal rotor brake, even if I had to prepare a fire exstiguisher so to speak because of risk of overheated brakes. Dont start braking too soon because this is a waste of potential. And report this for inspection, it looks to me as the lesser evil.
- look for a good shelter : Vortices or gusts create an extra danger. Buildings can indeed be dangereous because they create strong vortices, natural protection such as trees (tree lines) can have less vortices (unless it storms and you have branches flying around..).
d3