Troubling story and some questions

wrote:
Then I got into some real lift and pointed the
nose down and noticed my Becker transponder registering 18.2k which
is, of course, a no no.

Not really - our 18,000' limit is measured with the altimeter, typically
set by adjusting it to field elevation (msl) while on the ground. Your
transponder was reporting the altitude measured by the encoder, which is
set to 29.92 to measure "pressure altitude". These two measurements can
vary by a thousand feet or more at 18,000', depending on the weather.

As some of the other posters have pointed out, determining flutter
speeds is a tricky business. "Fundamentals of Sailplane Design"
discusses altitude effects on pages 58-60, indicating the "constant TAS"
limit is generally very conservative, but it's best to stick to the
flight manual or contact the manufacturer for guidance.

The flight manual for my ASH 26 E uses a combination of constant IAS and
constant TAS for Vne: it's constant IAS up to 10,000', and essentially
constant TAS above that. That TAS value is equal to Vne (IAS) at 10,000'.

I recommend the "Fundamentals..." book be on every glider pilot's
bookshelf, and that the pilot read it through at least once. It's a
great resource, and a better place to start than wading through a bunch
of hits by Google.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Dec 31, 10:21�am, Eric Greenwell wrote:
wrote:
Then I got into some real lift and pointed the
nose down and noticed my Becker transponder registering 18.2k which
is, of course, a no no.

Not really - our 18,000' limit is measured with the altimeter, typically
set by adjusting it to field elevation (msl) while on the ground. Your
transponder was reporting the altitude measured by the encoder, which is
set to 29.92 to measure "pressure altitude". These two measurements can
vary by a thousand feet or more at 18,000', depending on the weather.

As some of the other posters have pointed out, determining flutter
speeds is a tricky business. "Fundamentals of Sailplane Design"
discusses altitude effects on pages 58-60, indicating the "constant TAS"
limit is generally very conservative, but it's best to stick to the
flight manual or contact the manufacturer for guidance.

The flight manual for my ASH 26 E uses a combination of constant IAS and
constant TAS for Vne: it's constant IAS up to 10,000', and essentially
constant TAS above that. That TAS value is equal to Vne (IAS) at 10,000'.

I recommend the "Fundamentals..." book be on every glider pilot's
bookshelf, and that the pilot read it through at least once. It's a
great resource, and a better place to start than wading through a bunch
of hits by Google.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes"http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

http://711reporting.blogspot.com/

# 711.