On Friday, April 10, 2015 at 9:02:23 PM UTC-7, wrote:
"Its also worth mentioning that Vne is not based on load factor, like Va, but on flutter, which is why its True and not Indicated. "

Actually flutter is dependent on equivalent airspeed not true airspeed. There was an interesting article in Soaring magazine way back where Stan Hall brought in a NASA aerodynamic expert specializing in aeroelasticity and had his work peer reviewed by other experts to try and get a definitive answer on a flutter question arising from a flutter accident that led to several months of "argument by letter to the editor."

"In my glider, the placard VNE is 146 knots IAS but at 18,000 ft this is reduced to 122 knots IAS" Which brings up a question I've never been able to get a good answer to: what methodology do they use to determine reduced VNE with increasing altitude? Many gliders specify just IAS and the gliders I've dealt with which do specify lower VNE's with increasing altitude don't have those speeds match up with TAS at those altitudes. Calculate what TAS at 18,000 for an IAS of 122 knots actually is. It's higher than 146 knots.

As for the original question: where I fly the clouds are filled with granite up to 7000 feet or more, the valleys are narrow and the valley floors are not much above sea level. I don't have a turn and slip or AH and I have only had minimal training on those instruments over a decade ago in a Piper Cherokee. Being caught in cloud where I fly I would probably opt for the parachute pretty damn quick. That however is just the best of a bunch of bad options really.

In a cloud, it would be best to observe the max maneuvering airspeed which reliably tracks IAS but is usually considerably below Vne.

As I understand it, the flutter dynamics do not change at the same rate as dynamic pressure which is proportional to air density and V^2 therefore TAS is proportional to delta density^0.5. The coefficient for flutter in somewhere between 0.5 and 1 so the flutter speed increases, but not as fast as TAS increases with falling density. A lot of flutter has to do with dampening, I suppose in thinner air there is less.

I don't think many modern gliders are actually tested to flutter, I believe you are allowed to use computed numbers now for cert.