Hi Guys,
I've been watching some spotter videos on Youtube recently, featuring multiple takeoffs of the 787. I have noted an interesting behaviour oft he flaperons during the takeoff roll. At the begining of the roll, they seem to be positioned straight, around zero degrees, forming a visible gap between deflected flaps. Then, around 80-ish kt (?) they deflect downwards, flush with the flaps to seal the gap and provide additional lift.
An example can be seen here at 6:18, 11:42 and 20:50:
- both flaperons deflect downwards symmetrically at some speed. It happens on all takeoffs and in my opinion does not have to do with the control wheel deflection due to crosswind.
Any idea behind this logic?
Also, a bonus question - does anyone have any more background info on how the cruise flaps work? Boeing devoted just one small paragraph in the FCOM to their operation, with virtually no explanation. Do they move the Center of Pressure, as in the A350, or do they modify Cl? Do they always deflect downwards, or can they move up as well?
Cheers,
SnR