An other big falsehood :
Balsamo says :
the aircraft prototypes are subject to high speeds in the wind tunnel. When the aircraft develops an onset of buffeting, flutter, instability, CG v CP.. .etc, Vd is set
The two biggest wind tunnel (at NASA Ames Research Center)
12x24 meters for speed up to 300kts
24x36 meters for speed up to 100kts
Wind tunnel tests are used to measure the velocity around, and forces or pressures upon some structures of the plane, not the VD of a real plane as big as a 767.
Today, finite element analysis and computational fluid dynamics modelling are used to estimate the structural limits,
but VD is not the structural limit.
VD is a FAA certification speed representing a
security margin on the cruise speed.
a 7.5° pitch down of 20 seconds (approx 1.15VC)