Many thanks for your clear and detailed reply.
At least I have my answer to this left stick force that I had to counteract using the trim knob.
May I add that I’m a bit surprised by the fact that, as you mentioned, the tranverse fllow effect be “short lived”.
Even tough I totally agree that the air acceleration difference between the front and the rear part of the rotor disc is at its most value during ETL, shouldn’t we still “feel” the right roll tendency at greater airspeed due to the rotor disc tilt to the front during the cruise ?
I remember reading about this subject in the “Cyclic and Collective” Mr Shawn Coyle ‘s book citing that you could feel this tranverse flow roll during a zero ground speed hover with a side wind for example. So I imagined that , with a moderate wind, you could be above ETL and still have to counteract this roll….
Anyway, many thanks again for your for your answer, it was a subject that I had difficulties for explaining to my students.
ps : please forgive me for my “frenchy” english style…..and mistakes…

And remember, when pulling up the cyclic trim knob, be sure to reach around the left side of the cyclic, thereby reducing the likelihood of accidentally pulling up the mixture knob which is to the right of the trim knob.

The transverse flow effect “roll” to the left is short lived and predominatly only encountered during the initial acceleration phase as described in the original article.

Even if I totally agree with this phenomenon, I still can’t explain what’s happening when I fly the R22 model.
One year ago, I exchanged very interesting e-mails with Ron Newman, the author of the excellent “Helicopters will take you anywhere” about this transverse flow effect and what I could feel and read about the R22 on this case. Here is an excerpt of what I wrote to him at this time :

“….And when I consult the R22 ‘s POH, page 7-5, systems description, control trim and friction, I can read :

” The lateral cyclic is equipped with an on-off trim spring to cancel the left stick force which occurs during high speed flight.”

There is for sure a left stick force increasing, but, as for me, it seems to go against the transverse flow effect theory with a counterclockwise rotor type (viewed from above) ?

Furthermore, when I read the Special Investigation Report of the NTSB about the “Robinson Helicopter Company R22 Loss of main rotor control accident” (NTSB/SIR-96/03)(see attached file), you can read about the FAA’s review on flight testings of R22 and R44 models, page 23, second paragraph :

” the tests showed that, during cruise, the cyclic is forward and to the right of neutral, while the rotor plane is tilted aft and to the left, about 5° “.

Statements which whom I agree too, speaking only about the cyclic position, but…….why ?

Ron Newman told me that he couldn’t explain this statement and that he would ask for clarification with Tim Tucker of Robinson’s factory.

Unfortunately, I don’t have the answer yet.

Maybe you’ll have the solution ?

Yes, the rear portion does NEED more angle of attack, but since it doesn’t get said increased angle of attack (it is actually reduced angle of attack due to the downwash), the resultant increased lift of the nose of the helicopter (and the end result of increased left side lift because of GP) occurs, causing the rotor disk to tilt to the right.