|Quoting Boeing nut (Reply 8):|
I believe it to be feasible because I know at one point, McDonnel Douglas was considering "flaperons" for the MD-11 upgrade some years back.
The 777 has flaperons, namely the inboard ailerons also function as flaps but still move as ailerons as well.
The idea here has to be: Is it really beneficial?
What's the purpose of reducing this little vortex? Is it to increase efficiency (by decreasing drag) or to decrease wake turbulence?
If it's to decrease drag, well, at higher flap settings, the flaps are designed to create more drag. The 757 you see in the picture is very slippery. If you fly a normal ILS in one, you'll have a touch time bringing your speed down to final approach speed during the final glideslope descent, if you didn't have the extra drag. Furthermore, you need "engine spool-up" which is a higher thrust setting, during the final part of the approach. This is required in case of a go-around. Big jet engines take a long time to spool-up to high thrust, and if your thrust was at or just above idle, the engines would take TOO long. It's a legal requirement. So the drag is needed.
If it's to reduce wake turbulence, well, the wing vortices are much more significant than the flap vortices. With current separation minima, there are no problems at all regarding flap vortices. Minimum separation on final is usually 3 nm, cutting that any shorter would increase risk of go-around if the preceding aircraft wasn't able to clear the runway. So the 3 nm seperation is just fine.