Intruder -
757/767 has almost exactly 50% reduction in stall speed for the flap movement.
However, we operate in 20 kt speed reductions allowable per flap configuration, which is not the same thing as the actual reduction in stall speed.
Are you positive the you're commenting on actual stall speeds vs. SOP speeds per flap configuration? They're two different situations. I'm asking because a 747 classic pilot told me that the stall reduction for the first notch (or two?) of flaps on the 747 had a similar impact(high percentage of total stall speed reduction).
757 - 200K 767-300 320K
0 - 151 0- 172
1- 125 53% decrease 1- 142 56% decrease
5- 118 5- 130
15- 113 15- 127
20- 109 20- 125
25- 104 25- 120
30- 102 30- 118