Originally Posted by
washoutt
Could it be, that the exhaust and bypass air-gas stream is expanded at low speeds but contracts at higher speeds? The wide gasstream could affect a deployed flaperon, so it's pulled up, but a narrower stream will allow the flaperon to be in line with the flaps, and increase the effectivity during take off.
Thanks, I was thinking along the same lines.
Another explanation I thought of was some sort of direct lift control via the flaperons - the takeoff technique on the 787 is to initiate the roll with a slight forward deflection of the control column and relax it at 80 knots - it more or less co-incides with the flaperons deflecting downwards. However, there’s no mention of anything like it in the FCOM.