Catchup,
Yep, aircraft is more
speed-stable with a higher flapsetting. However, with higher flapsetting, the difference in wing-loading when viewed spanwise increases, effectively generating more lift at the centre & root of the wing and proportionally (due to reduced speed) less at the tips. This would imply that the aircraft is less statically stable in the roll channel, and indeed, that is what is observed on (at least) the 737 when going from F30 to F40.
The speed-difference between the 2 flaps-settings is only in the order of 3-5 kts (about 3,5%), so the difference in actual drift angle to overcome is subtle.
Does anybody know if the increased gap between trailing edge/aileron and the flaps (and therefore the size of the generated vortex & the effect on spanwise flow) has anything to do with the decreased static roll stability?
Brgds,
Empty
