Minumum Sink Rate/Best L/D at 17,000 feet ?

On Jan 2, 7:13*am, Andy wrote:
On Jan 1, 4:52*pm, wrote:

One interesting experiment would be to deflect the wings on the ground
and release them - with and without water - and measure the difference
in the frequency of the oscillations.

That would be of interest if the flutter limit speed was set by
primary wing structure, *Is it, or do the control surfaces flutter
first.

In my experience in transport aircraft flight test the flutter testing
is always done with maximum allowable free play in control linkages.
Do glider manufacturers do that, it not, does flutter speed reduce as
control links wear?

Andy

I think the flutter mode which occurs first may change with altitude,
the generation of glider, and wear, excluding the pilot induced mode.
Since the optimization of structures for operating under 6000m, I
would suspect dynamic flutter to occur first at lower altitudes, but
elastic flutter to occur first at higher altitudes, say above 8-9000m,
as the center of pressure shifts. Dynamic pressures are more directly
related in IAS, rather than TAS. Elastic modes are related to TAS.
IIRC, spar placement in modern designs is not as resistant to elastic
twisting at higher altitudes.

Frank Whiteley