Originally Posted by
whatbolt
I believe this came about after some tests from Boeing which proved that the lift/stall features of the wing changed significantly with various seals missing/damaged on the slats. I think there was an in flight occurance which triggered this investigation.
Sounds unlikely for something where you're only applying a clean config penalty. Perhaps the WUSS-to-slat seal, maybe. I'm more tempted to guess that it's being applied only to the clean config because the basic drag is much lower, so the delta due to the missing seal is proportionally greater. With all the mess of gear and high lift devices dangling in the wind, it may not be as significant.
Also, if you were suffering stall characteristics changes, and yet not adjusting speeds to account for stall speed changes ... again, sounds a bit odd.