An interesting thing has come to my attention as I browse photos of MD-11s in action. It appears that while the MD-11 is able to use both inboard and outboard ailerons simultaneously as flaperons, to augment flap function much as the 777 does, in some cases, it is clear that they are not used, and the MD-11 wing in those cases appears to function exactly as its predecessor, the DC-10 (i.e. just flaps, while inboard and outboard ailerons are flush).
Why is this? What flight management decision governs whether a crew will program the system to droop ailerons for flap augmentation, or not?