"Arnold Pieper" wrote in
message
om...
| Eric,
|
| Thanks, I see how explicit they are about it.
| DG chose to not get into specifics, because the story is a
bit more complex
| than that.
|
| The VNE of your glider is 146Kt (IAS), but above 10000'
you should start
| observing other IAS limits, that translate into 162Kt TAS
due to flutter
| considerations.
|
| Therefore, simply using 146Kt as a TAS value is not
correct, which is what
| was being suggested earlier, and is what I had trouble
with.
|
| Nowhere in Aeronautic literature is VNE defined as a TAS
value, it HAS to be
| presented to the pilot as Indicated.
|
| In high-performance aircraft where flutter is less of a
consideration, there
| is no such table for high altitude, VNE is always VNE,
until MMo becomes a
| factor.

I think the statement that you should use TAS as the limit
for Vne rather than IAS, comes from earlier times, when less
was known about instabilities such as flutter. I have heard
it said that something between IAS and TAS is what affects
flutter, but the percentage will change from one aircraft to
another, so it is safe to use TAS as a Vne limit. No one
said it was an exact statement, but it is known to be
*safe*.
TAS is calculated by power pilots as a matter of course for
flight planning, so the conversion is well known and easily
available on the various flight computers ("prayer wheels"
and such)
It is sometimes mandated by local Authorities that a table
based on manufacturer's data or TAS is provided.
The Gliding Federation of Australia has such a stipulation,
tied to the installation of oxygen in a glider. Part of the
installation is a placard to be fixed in the cockpit which
shows the table of Indicated Vne versus altitude, derived
either from the manufacturer's table or calculated using TAS
conversion for a standard atmosphere (pressure and
temperature with height)
Whether either table is "right" is immaterial, as long as
the table gives the pilot *safe* information.
Cheers, John G.