why is Vne a TAS?

"private" wrote
"Flutter limits high true airspeed operations, and it is possible to
get to the coffin corner where stall speed and Vne approach each
other."
Can I have the groups wisdom and further explanation of the reasons
for this and of how Vne changes with altitude.


It is probably not "flutter" that sets the high speed limit, but
rather "critical Mach bufett". Yes, even a glider has a Mmo but
no mach meter to indicate it, so an equivalent TAS becomes the limit.

Copied from a web site:

"The critical Mach number is the free stream Mach number at which sonic
flow first appears on the airfoil/wing.

Buffeting is the structural response to excitation produced by the shock-
induced flow separation, and is ultimtely related to the vortex formation
and breakdown. Buffeting may affect different parts of the airframe, but
the buffeting on the wing is the most important.

As the speed increases the wing is affected by shock stall, whose
appearance sets an upper limit to the speed. This limit is a function of
the flight altitude. Its envelope is called buffeting boundary."

Bob Moore

Bob Moore wrote:

It is probably not "flutter" that sets the high speed limit, but
rather "critical Mach bufett". Yes, even a glider has a Mmo but
no mach meter to indicate it, so an equivalent TAS becomes the limit.

The typical Vne for gliders is around 150 knots. Pretty low for mach
buffets.

If you want to see what flutter is, look he
http://www.dg-download.de/Videos/dg-...terversuch.mpg

Stefan

"Stefan" wrote

If you want to see what flutter is, look he
http://www.dg-download.de/Videos/dg-...terversuch.mpg

Ooooohh, THAT looks VERY scary! I had never seen such large amplitude
flutter before. I had always seen small buzzing types of flutter. I hope I
never see either kind, except in a video.
--
Jim in NC

Morgans wrote:

If you want to see what flutter is, look he
http://www.dg-download.de/Videos/dg-...terversuch.mpg

Ooooohh, THAT looks VERY scary! I had never seen such large amplitude
flutter before. I had always seen small buzzing types of flutter. I hope I
never see either kind, except in a video.

It was a test flight with a specially reinforced glider. Any production
glider would have lost its wings pretty quickly.

Stefan

("Morgans" wrote)
If you want to see what flutter is, look he
http://www.dg-download.de/Videos/dg-300-flatterversuch.mpg

Ooooohh, THAT looks VERY scary! I had never seen such large amplitude
flutter before. I had always seen small buzzing types of flutter. I hope
I
never see either kind, except in a video.


....when those new piezoelectric wings short circuit. g

BTW, if flutter happens what do you glider pilots do:
Nose up?
Nose down?
Start speaking German?


Montblack

Montblack wrote:

BTW, if flutter happens what do you glider pilots do:
Nose up?
Nose down?
Start speaking German?

Use the chute.

Stefan

BTW, if flutter happens what do you glider pilots do:
Nose up?
Nose down?
Start speaking German?

They say the same thing we do, only in German it's one word instead of
two and two syllables instead of one.

In article ,
john smith wrote:

BTW, if flutter happens what do you glider pilots do:
Nose up?
Nose down?
Start speaking German?

They say the same thing we do, only in German it's one word instead of
two and two syllables instead of one.

The Norwegian term is "Uff Dah!"

In article ,
"Montblack" wrote:

("Morgans" wrote)
If you want to see what flutter is, look he
http://www.dg-download.de/Videos/dg-300-flatterversuch.mpg

Ooooohh, THAT looks VERY scary! I had never seen such large amplitude
flutter before. I had always seen small buzzing types of flutter. I hope
I
never see either kind, except in a video.


...when those new piezoelectric wings short circuit. g

BTW, if flutter happens what do you glider pilots do:
Nose up?
Nose down?
Start speaking German?


Montblack

Bail out! Catastrophic flutter can occur and destroy the structure in
less than 2 seconds.