Overspeed Recovery question

On Wednesday, February 11, 2015 at 2:30:06 AM UTC-8, Don Johnstone wrote:
At 02:58 11 February 2015, wrote:
If you inadvertently fly into the yellow range and kiss the red range,
and
=
you get into the high speed vibration, what is the best way to slow
before
=
the wings depart the glider. My sense is to reach for the spoilers and
slo=
wly extend to slow. Any opinions on that matter?

A very experienced test pilot once told me, and several others, that if you
were faced with exceeding VNE you should pull as hard as you can, even if
it means exceeding max G load, to reduce speed as soon as you can to below
VNE. Catastrophic structural failures due to excess G are very rare unless
there are other factors, catastrophic failures due to flutter are almost
inevitable.
There is no right answer, just a less wrong one and I would stress I have
not had the opportunity to test this.
One of the requirements on a Grob 103 post major inspection test flight was
to operate the spoilers at 70kts, having done this many times I would not
recommend the spoilers option.

Since flutter is a dynamic phenomenon related to wing stiffness, I could make a theoretical argument that loading the wing would help. But I am not going to test it.

There are a lot of pilots flying up in the mountains where I fly that are unaware that just because the placard says 146 knots IAS or whatever, that is not true at FL180. On my glider, 146 knots IAS at 10,000 ft, 122 at 18,000, 76 at 42,000.

Well here is what I did. I was flying behind an ASW24 in my LS6. We were comparing how the two ships performed while doing some wing overs and other stuff to burn off some excess altitude. At the top of the last wing over, the pilot in front of me rolled it inverted and pulled it in to a Split S. Without thinking about it too much I repeated the Split S a few seconds later. The rapid advance of the ASI towards red line was impressive and relentless. I pulled back some, nothing much happened, I pulled back some more, nothing much happened, I pulled the stick back to the stop and started cursing at everyone involved in this stupid decision, and finally the nose came back to a normal distance below the horizon rather than its previous straight down orientation. Nothing broke, cracked, acted weird, or got bent, but when I conferred with the other pilot on the ground, we both decided that we were not going to do that again, and we both needed a beer before going home.

SF

On 2/11/2015 11:25 AM, SF wrote:
Well here is what I did...
Snip...
Without thinking about it too much I repeated the Split S a few seconds
later. The rapid advance of the ASI towards red line was impressive and
relentless.

Between this and JJ's recent "thunderstorm" thread, methinks we're seeing
evidence of winter in the northern hemisphere; contributors are willing to
share some survived sillinesses! That's a good thing, and I thank all for sharing.

I happened to read the original question posed in this thread ("If you
inadvertently fly into the yellow range and kiss the red range, and you get
into the high speed vibration, what is the best way to slow before the wings
depart the glider. My sense is to reach for the spoilers and slowly extend to
slow.") late in the PM before retiring to Zonkland, and will admit the
2nd/declarative sentence, and a personally compelling interest in soaring
safety, triggered a mental alarm bell. I'll elaborate on "Why?" shortly.

But first, even if the question is simply a cleverly designed attempt to
initiate a broad-in-scope discussion (as distinct from reflecting the O.P.'s
personal/presently-felt state of knowledge), it's a good one! The devil is
always in the details, and the details of gliders' load-bearing construction
commonly include structures composed of wood, steel tube and fabric, sheet
aluminum, 1st-generation fiberglass, and carbon fiber. Each has distinctly
different toleration to "high speed vibration"...which itself is a concept
worthy of lengthy definition, perhaps! Bottom line is these details may prove
to be compellingly important to Joe PIC, particularly in the time granted by
the structure to implement "the proper response." Arguably, 1st-generation
glass structures may simultaneously be most likely display to "high speed
vibration", and, to grant Joe PIC the greatest length of time to correct it
before something disastrous happens to the structure; wood and sheet metal may
be least generous with pre-failure time. Regardless of structure, "high speed
vibration" *will* get your attention...as well it should!

I could be reading way too much into original question/and "sense" of the
O.P., but here's why the sentence pair triggered an alarm bell. Is any reader
aware of any glider manufacturer's ship documentation that recommends as the
*first* corrective step for anything (other than pattern work, and perhaps,
tow-related height correction) to open the spoilers? Others have sensibly
noted several structural reasons that doing so at "too high a speed" may be
distinctly unwise, and I'm a fan of undoing first what caused the
problem...which in the case of high speed, certainly wasn't the spoilers.

So...no snark intended in my original reply. Anyone who finds themselves with
a case of "inadvertent imminent overspeed" surely had BETTER be alarmed, and,
have a sensible, pre-planned course of action ready for immediate implementation.

Good, thought-provoking scenario...

Bob W.

P.S. My own glider thunderstorm story involves the usual "made sense at the
time" rationales, resulted in a go-around initiated on short final from the
full-flap condition in an HP-14, in blinding rain and strong lift, in order to
avoid an overshoot into a tree lined mini-canyon/defile. It happened with
somewhere between 300 and 400 total hours...and served as "fair warning"
regarding thunderstorms...not that I should have needed - or been granted -
any. Even though I got away with it, I really should've landed out at the last
usable field 10 or so miles away. My most compelling rationale for continuing
was a really lousy trailer, though wanting to complete the contest task played
a part too. As I recall, only 4 or 5 of 30 did...and it wasn't the
thunderstorm over the field that put 'em on the ground!

On Tuesday, February 10, 2015 at 6:58:58 PM UTC-8, wrote:
If you inadvertently fly into the yellow range and kiss the red range, and you get into the high speed vibration, what is the best way to slow before the wings depart the glider. My sense is to reach for the spoilers and slowly extend to slow. Any opinions on that matter?

Thanks all for your input. The senario as stated in my quest has happened to me several times whilst flying Condor - Glider flight Simulation software. I've been deploying spoilers to slow down but that I would ask this group in case it happens in a real glider. Your inputs, as I suspected, are well thought out and are convincing. My thoughts to control highspeed flight (overspeed flight) will be pitch.

At 23:07 11 February 2015, wrote:
On Tuesday, February 10, 2015 at 6:58:58 PM UTC-8,
wro=
te:
If you inadvertently fly into the yellow range and kiss the red range,
an=
d you get into the high speed vibration, what is the best way to slow
befor=
e the wings depart the glider. My sense is to reach for the spoilers and
s=
lowly extend to slow. Any opinions on that matter?

Thanks all for your input. The senario as stated in my quest has
happened
=
to me several times whilst flying Condor - Glider flight Simulation
softwar=
e. I've been deploying spoilers to slow down but that I would ask this
gro=
up in case it happens in a real glider. Your inputs, as I suspected, are
w=
ell thought out and are convincing. My thoughts to control highspeed
fligh=
t (overspeed flight) will be pitch.

My reluctance to recommend the spoilers is mainly, but not only, for
aerodynamic reasons, a scaphoid fracture is extremely painful, which is
best avoided unless faced with a life or death situation. The very loud
bang as the airbrakes hit the stop is more than a bit scary as well.

I was always taught that if you exceed VNE and open the spoilers, they will push the airflow outwards and snap off the wing tips. Never tested the theory but I'm not sure I want to.

On Wednesday, February 11, 2015 at 5:30:05 PM UTC-8, Don Johnstone wrote:
At 23:07 11 February 2015, wrote:
On Tuesday, February 10, 2015 at 6:58:58 PM UTC-8,
wro=
te:
If you inadvertently fly into the yellow range and kiss the red range,
an=
d you get into the high speed vibration, what is the best way to slow
befor=
e the wings depart the glider. My sense is to reach for the spoilers and
s=
lowly extend to slow. Any opinions on that matter?

Thanks all for your input. The senario as stated in my quest has
happened
=
to me several times whilst flying Condor - Glider flight Simulation
softwar=
e. I've been deploying spoilers to slow down but that I would ask this
gro=
up in case it happens in a real glider. Your inputs, as I suspected, are
w=
ell thought out and are convincing. My thoughts to control highspeed
fligh=
t (overspeed flight) will be pitch.

My reluctance to recommend the spoilers is mainly, but not only, for
aerodynamic reasons, a scaphoid fracture is extremely painful, which is
best avoided unless faced with a life or death situation. The very loud
bang as the airbrakes hit the stop is more than a bit scary as well.


I have extended the spoilers at over 100 knots IAS at 18,000 ft a few times (mainly to get out from under clouds) and I brace myself and wince with a death grip on the handle when I do it. Stuff is going to fly around and my head is probably going to hit the canopy. I sure wouldn't want to be doing that while the wings were fluttering.

If you can get to Williams, California on March 7-8...we are having AcroFest.
AcroFest is an introduction to glider aerobatics for the average glider pilot and an opportunity to learn what it feels like to fly upside down and how to get back upright.
We can show you how to recover from an overspeed.
We can show you how to safely get your upside down glider right side up.
We can let you experience a spin in our Fox and how to recover.
We fly both Saturday and Sunday.
We have presentations and a BBQ on Saturday evening.
Go to: www.williamssoaring.com
We fly ASK-21s and a Fox.

On Thursday, February 12, 2015 at 12:07:31 PM UTC+13, wrote:
On Tuesday, February 10, 2015 at 6:58:58 PM UTC-8, wrote:
If you inadvertently fly into the yellow range and kiss the red range, and you get into the high speed vibration, what is the best way to slow before the wings depart the glider. My sense is to reach for the spoilers and slowly extend to slow. Any opinions on that matter?

Thanks all for your input. The senario as stated in my quest has happened to me several times whilst flying Condor - Glider flight Simulation software. I've been deploying spoilers to slow down but that I would ask this group in case it happens in a real glider. Your inputs, as I suspected, are well thought out and are convincing. My thoughts to control highspeed flight (overspeed flight) will be pitch.

The flutter in condor is nasty, and happens at speeds well below where any real glider would probably experience flutter. The simulated glider also falls apart very very quickly!

Quickly pulling the nose up above the horizon is really the only sensible thing to do there.

On Wednesday, February 11, 2015 at 6:49:09 PM UTC-7, Bruce Hoult wrote:
On Thursday, February 12, 2015 at 12:07:31 PM UTC+13, wrote:
On Tuesday, February 10, 2015 at 6:58:58 PM UTC-8, wrote:
If you inadvertently fly into the yellow range and kiss the red range, and you get into the high speed vibration, what is the best way to slow before the wings depart the glider. My sense is to reach for the spoilers and slowly extend to slow. Any opinions on that matter?

Thanks all for your input. The senario as stated in my quest has happened to me several times whilst flying Condor - Glider flight Simulation software. I've been deploying spoilers to slow down but that I would ask this group in case it happens in a real glider. Your inputs, as I suspected, are well thought out and are convincing. My thoughts to control highspeed flight (overspeed flight) will be pitch.

The flutter in condor is nasty, and happens at speeds well below where any real glider would probably experience flutter. The simulated glider also falls apart very very quickly!

Have a lot of experience at that?