1.3 VS
Hi,
not a test pilot so happy to be corrected but my understanding of how 1.3 Vs is arrived at might be the following.
At the 3 degree glide path that most jets fly at ( based around maximum rate of descent that the gear can handle before overstress ( which I think is up to 640 fpm at max landing weight and 300 fpm at max to weight so I believe) there exists a speed that the aircraft rate of descent can be arrested in the flare. ( I even think there is a G rate for that somewhere) such that the airspeed bleeds off to achieve a speed of touch down just higher than the actual stall speed of the aircraft.
Stalling 250 tonnes of aluminium from even a few feet above a runway would be quite a shock to the jet.
So that is basically how they arrived at 1.3 - guess it works empirically.
Of note is that the Airbus family of FBW jets due to the protection measures in the flight controls are actually certified to slightly lower Vapp speeds if my memory serves me correctly.
Might be totally bogus answer but that is what I am lead to believe.
13000 hours total on both 777 and 330s 707s and stuff like that... but not an B Aero Eng.!