Originally Posted by
zzuf
....Don't forget that most certification standards require a safe landing from Vref minus some thing - usually 5 knots. I have seen a few light aircraft which cannot comply (at 1.3vso minus x), so Vref ends up being more than 1.3Vso. There may well be transport aircraft with the same situation.
Oh guaranteed. I can think of one immediately. (Engine power on approach and assuring adequate throttle response can be part of the constraints on Vref.)
And ANY transport category aircraft which has speed adders for failure cases which do not directly impact lift generating capability are implicitly in the same category. (If I am to fly at Vref+X for a hyd system failure, that implies at least a chance that the a/c cannot easily flare with the presumably reduced elevator authority, or has lateral control issues, for example)