Troubling story and some questions

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

On 12/30/07 11:03 PM, in article
,
" 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

Great story with a lot of lessons for all of us. I've got nothing to offer
about the U-2, but don't forget to file your NASA ASRS.

Flutter speed (the normal cause of the break-up you
are concerned about) varies with altitude but not so
much as does the IAS. As an example, if your flutter
speed is 180 knots at sea level, meaning you can fly
up to 179 knots IAS (and TAS) at sea level, if you
climb to an altitude where 180 knots TAS is 100 knots
IAS, you will probably be able to go up to abouit 140
knots IAS before flutter occurs.

Don't take that as definitive for your glider, it varies
from type to type.

Your 1.5% error per thousand feet only holds good over
a very limited altitude range, space does not start
at 67,000 feet.

At 06:06 31 December 2007, 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

Dave,



You had another option open to you other than pulling up to slow down to
extend brakes and therefore bumping higher into "no-no" airspace.



You could have maintained your airspeed but turned left or right to get
into weaker lift or light sink. Once you had lost enough altitude then
eased back over into the stronger lift regions.



Larry

"01" USA

Ventus 2bx







" wrote in message
:

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

On Dec 31 2007, 7:06 am, "01-- Zero One" wrote:
Dave,

You had another option open to you other than pulling up to slow down to
extend brakes and therefore bumping higher into "no-no" airspace.

You could have maintained your airspeed but turned left or right to get
into weaker lift or light sink. Once you had lost enough altitude then
eased back over into the stronger lift regions.

Larry

"01" USA

Ventus 2bx

" wrote in message

:

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

If I recall from training days, you can lose altitude faster in a
descending turn than you can in a straight line, even at the same
speed.
I don't think I can explain this late at night why I think this works,
but it sort of makes sense.

If I recall from training days, you can lose altitude faster in a
descending turn than you can in a straight line, even at the same
speed.
I don't think I can explain this late at night why I think this works,
but it sort of makes sense.- Hide quoted text -


It's due to the increased G's in a turn. Steeper turn, more G's, more
drag due to lift required to offset the Gs.

Same reason sink rate increases as you thermal steeper.

A bunch of G also helps keep the speed down in a steep, descending
turn (not a spiral, of course).

Perhaps time to hit the books again?

Kirk
66

Been there done that and glad you got home OK. High performance gliders are
hard to dive out of lift - they just go faster and keep climbing.

I'd suggest to all that, before you get into a situation like this, find out
how your spoilers react at airspeeds near Vne. Work up to it in 5kt
increments starting at 80 knots or so by cracking the spoilers open and
trying to hold them open just a crack.

You won't need much spoiler since the drag produced by them increases with
the cube of airspeed. Even if you need more, most spoiler systems are
fairly forgiving once cracked open so you can smoothly add more drag as
needed.

Bill Daniels



wrote in message
...
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

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.

What does your POH say about opening spoilers at high speed? Below
Maneuvering Speed (80 kts, I checked) it shouldn't be a big deal.
FWIW, I think you did the right thing in losing speed right now, rather
than thinking of the FAA implications. Could the feds ground you from
flying your ultralight anyway (probably)? ;-)


Shawn

What does your POH say about opening spoilers at high speed? Below
Maneuvering Speed (80 kts, I checked) it shouldn't be a big deal.
FWIW, I think you did the right thing in losing speed right now, rather
than thinking of the FAA implications. Could the feds ground you from
flying your ultralight anyway (probably)? ;-)

Forgive me if this strays from the thread a little, but I think it is
worth expanding on the relationships between maneuvering speed (Va),
spoilers and speeds/loads. Here is my understanding:

1. There is no relationship between Va (maneuvering speed) and
spoilers, except that Va is determined with spoilers retracted. Va is
based on pitch (elevator inputs). There is a general belief that
below Va you can do anything with any flight control, and the glider
cannot be damaged. This is may be true in some, perhaps many,
situations, but it is not true in any certification sense. [See EASA
glider regs CS 22.335]

2. Once spoilers are deployed, the loads for which the glider is
certified drop to +3.5 from +5.3 (utility) / +7.0 (aerobatic). [See
EASA glider regs CS 22.345]

For the reason stated in #2 above, "The Handbook of Glider
Aerobatics" (Mallinson and Woollard, 1999, page 30) states "It is
nearly always better to slow a glider by 'pulling g' rather than by
operating the airbrakes". They are speaking here of aerobatic gliders
(rated to 7 g's) during aerobatic maneuvers. There is some difference
in the loads/slowing that can be achieved by utility gliders. Also,
there are other considerations when using 'g' to slow (symmetric
loads, etc.). For the purposes of this discussion, I think I'm safe
with the summarization that the choice of spoiler over 'g' should not
be automatic in all situations.

This is not to say that spoilers may or may not have been an
appropriate response in the case being discussed, or many other
situations. Rather, I want to dissuade those who might feel that
spoilers are an appropriate response in every situation. Certainly
deploying spoilers and pulling high g's could be a catastrophic
combination.

I am certainly open to correction if there is an error in my analysis.

Regards,
Eric

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