On Saturday, November 9, 2019 at 12:49:14 PM UTC-6, jp wrote:
I know that Vne can vary with altitude but does it also vary with aircraft weight?

It might be more useful to use Vd rather than Vne, but in any case my guesstimate is that neither Vd or Vne varies with weight (mass), particularly if Vd is determined in a dive with no abrupt control deflections (white arc, right?).

I'm pretty sure calculating Vne employs a surprisingly arbitrary factor chosen to provide a safety margin of 10% below Vd (designed diving speed) which in turn is related to Vc, designed cruising speed. Various references suggest Vd can be either calculated or is the empirically derived maximum speed the test pilot attains before or when the aircraft experiences (1) flutter [Echo has it right I believe], (2) buffeting, (3) other signs of structural stress or (4) nothing [e.g., pilot instructed to go no faster than a pre-determined speed). Vne is a metric apparently not used in certification/testing, but is certainly part of the placard/POH.

Design Cruising Speed (Vc) = 33 * Sqrt (wing loading)
Design Dive Speed (Vd) = 1.4 * Vc
Never Exceed Speed (Vne) = 0.9 * Vd


Disclaimer: take this with a grain of salt, I am not fluent in aerodynamics