wing flattering in high altitude

[thru]

Is it corect/normal that in high altitude the max. speed is much lower?

For a DG with a max. of 270kmh the wings are flattering in a wave at e.g. 4-5000 meters
at 220-230kmh already! It happened to me already several times unfortunately, bumm, shock and free fall.

If the indicated air speed in the plane is 220kmh at 4000meters e.g. and there is, lets say no wind, so air speed=ground speed,
how much is the real ground speed? About 260kmh or so due to much lower density of the air?

Thank you, BR

[wickid]

Vne decreases approximately 1 kph per 100 meter altitude.

[MrHerisson]

I use CoTaSa to sound an alarm when i get close to VNE....it does adapt to altitude and prevents surprises

[dins]

To BR
in nil wind, forgetting earyths curvature, and assuming =level flight, TAS= ground speed, IAS at height is less than TAS, Flutter depends on TAS, not IAS, tghats why flutter in Condor correctly simulates the reduced speed at which fluttter happens (Really annoying when you are quite close to the ground at Grand Canyon or equivalent