On Dec 30, 10:03*pm, "
wrote:
Hi Gang
* Last week Minden had some excellent wave soaring. Off tow at 7.7k
msl and within minutes up to 18k. I decided to go up north skirting
Reno Intl. I had the transponder on and was monitoring Reno Approach.
My goal was to try and fly as fast as possible maintaining an altitude
very close to 18k by speeding up in lift and slowing down in light
lift or sink. This worked well for the first 35 miles where my IAS
(indicated air speed) *ranged between 50 knots and 110 knots flying
never less than 17k. 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. I then glanced at the IAS. It read 138 knots
which is 165 knots TAS. (Every 1000 feet of altitude above sea level
results in an error of 1.5% in IAS.) So what to do? If I pulled the
spoilers at that speed, the shock might destroy them or the glider. So
I gently pulled the stick back and translated speed into altitude
going above 19k. At about 70 knots I pulled the spoilers and got
myself down to below 18k. I wonder if ATC caught that? Why was this so
bad? Well the VNE at sea level for the SparrowHawk is 123 knots and it
has been demonstrated that at 171 knots the wings come off. This
really gave me cause for concern. How quickly one can get into trouble
by not paying attention. In the future I will fly slower and use the
spoilers to compensate for excessive lift so as to maintain altitude.
* This story raises some questions about VNE at various altitudes
which should be of interest to all of us glider pilots. I Googled
combinations of words such as "flutter altitude", "VNE altitude" and
"aircraft breakup altitude" to try and come up with information on
whether the flutter/breakup characteristics of an aircraft are less at
altitude than sea level at the same TAS. Intuitively it would seem so
but intuition may not work here. I found nothing useful. I know that
the World's ultimate high altitude motor glider the U2, which was
designed in the 50s, had much study done on it with regard to its
operating speed window of about 20mph (stall to breakup)at 80k feet
msl. There should now be declassified documents on those studies which
might answer my questions. I would appreciate any pointers anyone. If
I find anything useful I will summarize it on RAS.
* Flying is often unforgiving of errors and I will definitely be more
vigilant after this wake up call.
Dave

Should have rolled her inverted and pulled hard

On a more serious note.
Attention to the altlimeter when wave flying so close to class A is
imperative.
That and looking out for the Southwest jet about to run you down on
the Reno south approach.
As you had a transponder that is not the main issue here.

Your lesson was learnt I guess so don't do it again.

I had a similar over speed experience once in my SZD59.
I was doing Acro in the wave and after about 45mins made myself pretty
sick pulling G's...
So to chill out I just soared in the nice smooth wave lift.
I climb from about 10K up to 17K whilst regaining my composure for
another acro session.

By now I was feeling better I turn upside down and start flying along
inverted.
Bored with inverted straight and level I thought "I know lets try an
inverted circle"
Initiating the bank and still at around 17K I suddenly have that panic
feeling of "I cant push the stick far enough forward to stop the dive"
As the glider accelerated very quickly in the thin air if I pulled
through it would have broken the plane up.
My only way out was to roll upright and pull G's.

As I start my roll out the ASI is up around 170knots!!
I am rolling and starting to get the nose above the horizon now.
The pull out pulled 6.5G's and gave me tunnel vision during the pull
out.

It is a VERY strong and well balanced plane that SZD59.

That was the scariest moment I ever had in my soaring career!!

Happy New Year everyone

Regards

Al