Avoiding Vne

You are just plain wrong. The immediate effect of opening Schempp-Hirth
type airbrakes, if nothing else is done, is to make the wings bend more.

Have you ever tried opening the airbrakes with a bendy wing and watched what
actually happens?

When I flew an ASW20L I always used some landing flap when approaching to
land. Sometimes I would keep the brakes closed until near the ground. I
always opened them as I rounded out, because as soon as I did this the wings
bent up, to give me better ground clearance!

I remember flying a Skylark 3 at about 75 knots (fast for the type), at this
speed the tips bent down a bit, because of the washout. If I then opened
the airbrakes, the wings bent up.

Your theory is wrong, it does not work! Don't try to argue that I did not
see what I know I did see, get in something with bendy wings such as a
Pegasus, and try it.

I also remember seeing an article in "Technical Soaring" with a photo of a
Jantar 1 at Vne, and at 1 g., with the brakes fully out. The wing bend, at
1 g. remember, was horrendous. Don't try and give us some theoretical
reason why this cannot happen, it does!

You also say:
"all I want is to give my opinion when I think something is said here that
may lead to dangerous flying - such as sentences like "don't exceed VNE, but
no problem if you exceed permitted G-loading" ".
Who said that, which posting?

This whole discussion has been around the point, if you look as if you are
going to exceed Vne, what should you do?

Exceeding Vne is outside limits and dangerous, so are any of the
alternatives - the discussion is about which of the alternatives is the
least worst.

With the Minden accident on 13th July 1999, it is clear from the report that
the glider was pitched down to well beyond a 45 degree dive, so the
airbrakes would not have been speed limiting.

You say "I never experienced a spin recovery", presumably you mean in a
large span glider. I hope you have done plenty in training and short span
machines. An essential part of stall/spin recovery training is to be able
to distinguish at once the difference between a spin and a spiral dive. If
you treat a spiral dive as if it is still a spin, this is very likely to
lead to excessive speed, as well as using more height for the recovery.

I still think that the advice I gave in my first posting to this thread is
correct:
"If you exceed Vne you are taking a risk, if you pull too hard above
manoeuvring speed you are taking a risk, and if you pull hard and roll at
the same time you are taking a risk. If you pull the brakes you are
increasing the bending load on the wings.

"If you get it wrong and have to take one of the risks, I am told that you
should centralise the ailerons, then pull however hard is necessary not to
exceed Vne, and make sure the brakes stay shut."

Denis (Denis who and from where?), if you still feel like answering, please
answer what I have actually written.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Denis" wrote in message
...


W.J. (Bill) Dean (U.K.). wrote:

There were postings to Rec. Aviation Soaring when the report was
published, from pilots with experience of the Nimbus 4 and similar
models who had experience of inadvertent deployment of the airbrakes.
If the brakes deployed inadvertently while the pilots were recovering
from the dive, this surely may have been the reason for the amount of
bending seen; and for the overload which led to failure. Presumably
those investigating the accident were not aware of these incidents when
writing the report.


If airbrakes deploy inadvertently, the first effect (along with the very
high drag) will be a *decrease* in G-loading *and* bending moment), both
due to the loss of lift near the airbrakes. The increase of bending
would happen only after the angle of attack has been further increased
(voluntarily or not) to restore the initial G-loading with more lift on
the outer panels (instead of the airbrakes section), hence the higher
bending.


Denis, you are very scathing.


That is not my intention... all I want is to give my opinion when I
think something is said here that may lead to dangerous flying - such as
sentences like "don't exceed VNE, but no problem if you exceed permitted
G-loading".


What do you think went wrong?

What would you have done?

Do you have any experience in the Nimbus 3 & 4 series? I don't.

Are you more experienced or better than the pilots who did not make it?


I don't know them and I would not pretend to be better (there are no
good pilots, only old pilots...). And although I have some experience in
Nimbus 4D (more on ASH 25) I never experienced a spin recovery and I
hope I never will have to. Therefore I don't know what I would do in
such a situation. All I can say is what I think (sitting comfortably in
my chair) is the better thing to do, as I said in a previous post :

"If your speed is going to exceed VNE within this manoeuvre [pulling
up], you should stop or reduce pulling and apply full airbrakes. At any
dive angle up to 45° this prevents the glider to exceeding VNE, and you
have time to recover pulling gently (under 2 g's). This of course
supposes that there is sufficient ground clearance... "

Denis

At 18:54 29 March 2004, Denis wrote:
Pete Zeugma wrote:

you pull as hard as you need, and its not impossible
to know either, thats why you should practice spin
recovery.

AFAIK spin training is prohibited in most, if not all,
open class ships...

probably why we use k13's and puch's then and if you
are going to examine spin characteristics of big floppy
wings, you do it for spin entry and not any further.
but then again, you shouldnt be flying at a speed where
you are going to end up in a spin in the first place,
let alone suddenly realising that you've let your speed
build up to Vne! which is the whole point of spin training........



and presuming you have not blacked out by then also,
i start to grey out at about 7g from more than 5 secs
exposure at that level.

you would probably have blacked out about 9g

Yes, except grey out or black out happens only after
a few seconds (the
time needed for the blood to fall into your lower boby).


er.. didnt i say that? 5 secs....

And it is very
dependant of the condition and trainig of the pilot.

and seating position, and how much height exposure
he's had during the days flying........... (oxy saturation)

but then a well trained pilot wouldnt have got himself
into the position of entering a spin, let alone contemplating
what to do because hes suddenly at all the airframe
limits!


But a glider wing breaks within milliseconds of overstressing
!

no they dont, they have to fail progressivly. no glider
would be alowed in the air by any regulating body if
a wing could break in a 1000th of a second. i dont
think you really understand the force that would be
needed to do that. the instantanious g-load to do that
would kill you out right.



--
Denis

R. Parce que ça rompt le cours normal de la conversation
!!!
Q. Pourquoi ne faut-il pas répondre au-dessus de la
question ?

You may be correct. However, I have heard of some cases where there have been structural failures
resulting from excessive g-forces, but the glider has remained landable after that. Aerobatics books
also recommend to "pull as hard as necessary", but to keep an eye on your g-meter and ASI. High AoA
eats energy rather fast. Flutter from overspeeding will definately disintegrate your wing.
Excessive-g may not. The trick is to stay within the limits as long as possible. Therefore it's
necessary to know the limits and their use. In abovementioned Nimbus 4 incident it seems that pilot
exchausted g-limits before the Vne arrived. But no-one knows what really happened.

BTW, there is one energy-burning device on every glider that may save you the very necessary second
or two - the wheel. Lower it as soon as you feel the threat of overspeeding. You may lose the wheel
doors because of the speed and g-forces, but this is not nearly as catastrophical as losing wing
because of pulling the airbrakes at Vne and high-g.

You're both partially right. The moment you deploy the airbrakes and
maintain a constant angle of attack, you loose lift which means the glider
accelerates it's sink rate. G load decreases, bending decreases. Once the
sink rate is stabilized, the initial lift must have been restored but it's
different distribution along the wing span increases the bending.

BTW, Denis is fairly well know in France (an Morocco...)

--
Bert Willing

ASW20 "TW"


"W.J. (Bill) Dean (U.K.)." a écrit dans le message
de ...
You are just plain wrong. The immediate effect of opening Schempp-Hirth
type airbrakes, if nothing else is done, is to make the wings bend more.

Have you ever tried opening the airbrakes with a bendy wing and watched
what
actually happens?

When I flew an ASW20L I always used some landing flap when approaching to
land. Sometimes I would keep the brakes closed until near the ground.
I
always opened them as I rounded out, because as soon as I did this the
wings
bent up, to give me better ground clearance!

I remember flying a Skylark 3 at about 75 knots (fast for the type), at
this
speed the tips bent down a bit, because of the washout. If I then opened
the airbrakes, the wings bent up.

Your theory is wrong, it does not work! Don't try to argue that I did
not
see what I know I did see, get in something with bendy wings such as a
Pegasus, and try it.

I also remember seeing an article in "Technical Soaring" with a photo of a
Jantar 1 at Vne, and at 1 g., with the brakes fully out. The wing bend,
at
1 g. remember, was horrendous. Don't try and give us some theoretical
reason why this cannot happen, it does!

You also say:
"all I want is to give my opinion when I think something is said here
that
may lead to dangerous flying - such as sentences like "don't exceed VNE,
but
no problem if you exceed permitted G-loading" ".
Who said that, which posting?

This whole discussion has been around the point, if you look as if you are
going to exceed Vne, what should you do?

Exceeding Vne is outside limits and dangerous, so are any of the
alternatives - the discussion is about which of the alternatives is the
least worst.

With the Minden accident on 13th July 1999, it is clear from the report
that
the glider was pitched down to well beyond a 45 degree dive, so the
airbrakes would not have been speed limiting.

You say "I never experienced a spin recovery", presumably you mean in a
large span glider. I hope you have done plenty in training and short
span
machines. An essential part of stall/spin recovery training is to be
able
to distinguish at once the difference between a spin and a spiral dive.
If
you treat a spiral dive as if it is still a spin, this is very likely to
lead to excessive speed, as well as using more height for the recovery.

I still think that the advice I gave in my first posting to this thread is
correct:
"If you exceed Vne you are taking a risk, if you pull too hard above
manoeuvring speed you are taking a risk, and if you pull hard and roll at
the same time you are taking a risk. If you pull the brakes you are
increasing the bending load on the wings.

"If you get it wrong and have to take one of the risks, I am told that you
should centralise the ailerons, then pull however hard is necessary not to
exceed Vne, and make sure the brakes stay shut."

Denis (Denis who and from where?), if you still feel like answering,
please
answer what I have actually written.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Denis" wrote in message
...


W.J. (Bill) Dean (U.K.). wrote:

There were postings to Rec. Aviation Soaring when the report was
published, from pilots with experience of the Nimbus 4 and similar
models who had experience of inadvertent deployment of the airbrakes.
If the brakes deployed inadvertently while the pilots were recovering
from the dive, this surely may have been the reason for the amount of
bending seen; and for the overload which led to failure. Presumably
those investigating the accident were not aware of these incidents
when
writing the report.


If airbrakes deploy inadvertently, the first effect (along with the very
high drag) will be a *decrease* in G-loading *and* bending moment), both
due to the loss of lift near the airbrakes. The increase of bending
would happen only after the angle of attack has been further increased
(voluntarily or not) to restore the initial G-loading with more lift on
the outer panels (instead of the airbrakes section), hence the higher
bending.


Denis, you are very scathing.


That is not my intention... all I want is to give my opinion when I
think something is said here that may lead to dangerous flying - such as
sentences like "don't exceed VNE, but no problem if you exceed permitted
G-loading".


What do you think went wrong?

What would you have done?

Do you have any experience in the Nimbus 3 & 4 series? I don't.

Are you more experienced or better than the pilots who did not make
it?


I don't know them and I would not pretend to be better (there are no
good pilots, only old pilots...). And although I have some experience in
Nimbus 4D (more on ASH 25) I never experienced a spin recovery and I
hope I never will have to. Therefore I don't know what I would do in
such a situation. All I can say is what I think (sitting comfortably in
my chair) is the better thing to do, as I said in a previous post :

"If your speed is going to exceed VNE within this manoeuvre [pulling
up], you should stop or reduce pulling and apply full airbrakes. At any
dive angle up to 45° this prevents the glider to exceeding VNE, and you
have time to recover pulling gently (under 2 g's). This of course
supposes that there is sufficient ground clearance... "

Denis

That's correct. If you kill the lift over part of the
wing by opening the spoilers, the rest of the wing
needs to produce a higher coefficient of lift to keep
the glider from accelerating downward. This can only
happen through an increase in angle of attack. This
will cause the wing to flex more because the center
of lift has moved outboard (imagine lifting your glider
on the ground by the wingtips versus the wing roots
to appreciate the point).

If you don't increase the angle of attack to compensate
then liftweight and the glider will accelerate downward
(accelerating sink rate). In this case the outer panels
are producing no more lift (same aoa, same airspeed)
and the inner portion of the wing is spoiled so net-net
there is less lift, less bending moment and less flex
in the wings. However, this is a transient state since
we all naturally compensate for the loss of lifting
surface by pulling back ever so slightly on the stick
and loading up the tips - hence the extra flex.

It's hard to notice the aoa shift in flight because
you need a lower pitch attitude to maintain airspeed
(due to higher drag) at the same time that aoa goes
up to produce enough lift to hold the glider up. Remember
pitch attitude and aoa are not the same.

Try going from dive brakes closed and locked to fully
open on landing rollout - AFTER you're sure you have
the tailwheel down. In this case aoa should be held
pretty constant. See what the wings do then.

9B


At 07:54 30 March 2004, Bert Willing wrote:
You're both partially right. The moment you deploy
the airbrakes and
maintain a constant angle of attack, you loose lift
which means the glider
accelerates it's sink rate. G load decreases, bending
decreases. Once the
sink rate is stabilized, the initial lift must have
been restored but it's
different distribution along the wing span increases
the bending.

BTW, Denis is fairly well know in France (an Morocco...)

--
Bert Willing

ASW20 'TW'


'W.J. (Bill) Dean (U.K.).' a écrit dans le message
de ...
You are just plain wrong. The immediate effect of
opening Schempp-Hirth
type airbrakes, if nothing else is done, is to make
the wings bend more.

Have you ever tried opening the airbrakes with a bendy
wing and watched
what
actually happens?

When I flew an ASW20L I always used some landing flap
when approaching to
land. Sometimes I would keep the brakes closed until
near the ground.
I
always opened them as I rounded out, because as soon
as I did this the
wings
bent up, to give me better ground clearance!

I remember flying a Skylark 3 at about 75 knots (fast
for the type), at
this
speed the tips bent down a bit, because of the washout.
If I then opened
the airbrakes, the wings bent up.

Your theory is wrong, it does not work! Don't try
to argue that I did
not
see what I know I did see, get in something with bendy
wings such as a
Pegasus, and try it.

I also remember seeing an article in 'Technical Soaring'
with a photo of a
Jantar 1 at Vne, and at 1 g., with the brakes fully
out. The wing bend,
at
1 g. remember, was horrendous. Don't try and give
us some theoretical
reason why this cannot happen, it does!

You also say:
'all I want is to give my opinion when I think something
is said here
that
may lead to dangerous flying - such as sentences like
'don't exceed VNE,
but
no problem if you exceed permitted G-loading' '.
Who said that, which posting?

This whole discussion has been around the point, if
you look as if you are
going to exceed Vne, what should you do?

Exceeding Vne is outside limits and dangerous, so
are any of the
alternatives - the discussion is about which of the
alternatives is the
least worst.

With the Minden accident on 13th July 1999, it is
clear from the report
that
the glider was pitched down to well beyond a 45 degree
dive, so the
airbrakes would not have been speed limiting.

You say 'I never experienced a spin recovery', presumably
you mean in a
large span glider. I hope you have done plenty in
training and short
span
machines. An essential part of stall/spin recovery
training is to be
able
to distinguish at once the difference between a spin
and a spiral dive.
If
you treat a spiral dive as if it is still a spin,
this is very likely to
lead to excessive speed, as well as using more height
for the recovery.

I still think that the advice I gave in my first posting
to this thread is
correct:
'If you exceed Vne you are taking a risk, if you pull
too hard above
manoeuvring speed you are taking a risk, and if you
pull hard and roll at
the same time you are taking a risk. If you pull
the brakes you are
increasing the bending load on the wings.

'If you get it wrong and have to take one of the risks,
I am told that you
should centralise the ailerons, then pull however
hard is necessary not to
exceed Vne, and make sure the brakes stay shut.'

Denis (Denis who and from where?), if you still feel
like answering,
please
answer what I have actually written.

W.J. (Bill) Dean (U.K.).
Remove 'ic' to reply.


'Denis' wrote in message
...


W.J. (Bill) Dean (U.K.). wrote:

There were postings to Rec. Aviation Soaring when
the report was
published, from pilots with experience of the Nimbus
4 and similar
models who had experience of inadvertent deployment
of the airbrakes.
If the brakes deployed inadvertently while the pilots
were recovering
from the dive, this surely may have been the reason
for the amount of
bending seen; and for the overload which led to
failure. Presumably
those investigating the accident were not aware
of these incidents
when
writing the report.


If airbrakes deploy inadvertently, the first effect
(along with the very
high drag) will be a *decrease* in G-loading *and*
bending moment), both
due to the loss of lift near the airbrakes. The increase
of bending
would happen only after the angle of attack has been
further increased
(voluntarily or not) to restore the initial G-loading
with more lift on
the outer panels (instead of the airbrakes section),
hence the higher
bending.


Denis, you are very scathing.


That is not my intention... all I want is to give
my opinion when I
think something is said here that may lead to dangerous
flying - such as
sentences like 'don't exceed VNE, but no problem
if you exceed permitted
G-loading'.


What do you think went wrong?

What would you have done?

Do you have any experience in the Nimbus 3 & 4 series?
I don't.

Are you more experienced or better than the pilots
who did not make
it?


I don't know them and I would not pretend to be better
(there are no
good pilots, only old pilots...). And although I
have some experience in
Nimbus 4D (more on ASH 25) I never experienced a
spin recovery and I
hope I never will have to. Therefore I don't know
what I would do in
such a situation. All I can say is what I think (sitting
comfortably in
my chair) is the better thing to do, as I said in
a previous post :

'If your speed is going to exceed VNE within this
manoeuvre [pulling
up], you should stop or reduce pulling and apply
full airbrakes. At any
dive angle up to 45° this prevents the glider to
exceeding VNE, and you
have time to recover pulling gently (under 2 g's).
This of course
supposes that there is sufficient ground clearance...
'

Denis

When I made my original post on this subject my contention
was quite simple, if faced with the choice of exceeding
VNE or pulling to avoid exceeding VNE and overstressing
the glider I would choose the latter. I would hope
that I would never get to the situation where I had
to do either and if I keep my wits about me I never
will. I stand by what I said but this was not an original
thought, it was the advice of someone who knows a great
deal more than me.

An earlier posting said 'Also, I find it a bit strange
that some here feel that it is possible to over-G a
sailplane to damage, but
not destruction. It seems like a fine point to me and
there are several examples of unlucky souls who have
misjudged the point'. Of course it is possible but
I accept it is purely a matter of luck. I never made
the above statement, I did say that overstress may
cause serious damage, but flutter is much more likely
to be catastrophic.

With some gliders there is such a large margin between
placarded limits and the forces the airframe will withstand
that overstressing is definitely the lesser of 2 evils.
The Grob Acro is a perfect example of this. One of
the Acros delivered to the RAF in the UK in the 80's
was given to Slingsbys to test on a rig. After the
'normal' testing (The wing spigot problem was discovered
in this test and I was told that had this failed in
flight the airframe would probably have stayed in one
piece). Following this attempts were then made to break
the glider but despite every effort the only thing
that broke was the test rig, the glider never did.
There is no such margin for the onset of flutter. Not
all gliders have the strength of the Grob I would agreed
but there is still a margin of some sort.

The way the whole thing was explained to me was that
pulling excess G may break the glider, in particular
it may cause damage to the wing/fuselage fixing but
this damage is not necessarily total (See above re
wing spigot problem). The damage caused by flutter
is much more likely to cause total failure not only
of the wing but other aerodynamic surfaces as well
(the tailplane and fin) and a glider without a tailplane/fin
is not where I would want to be. I am told that the
weakest point on any glider is the fuselage just in
front of the fin. Again I am told that when an aircraft
breaks up in flight the cause is almost invariably
flutter, the result of overspeed, whether this is preceeded
by overstress causing loss of control or not.

There has been a lot of use of words such as rubbish
and other derogatory terms. You do not have to agree
with me but I would suggest that perhaps you might
be better researching and then posting a cogent argument
why I am wrong instead of just gainsaying. (Remember
the Python :-) UK joke)

I stand by my original post, faced with the choice
of exceeding VNE or pulling too much G I would chose
the latter as the lesser of two very great evils.

Don, I agree with you completely. You have made the points which I have
been trying to put.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Don Johnstone" wrote in
message ...

When I made my original post on this subject my contention
was quite simple, if faced with the choice of exceeding
VNE or pulling to avoid exceeding VNE and overstressing
the glider I would choose the latter. I would hope
that I would never get to the situation where I had
to do either and if I keep my wits about me I never
will. I stand by what I said but this was not an original
thought, it was the advice of someone who knows a great
deal more than me.

An earlier posting said 'Also, I find it a bit strange
that some here feel that it is possible to over-G a
sailplane to damage, but not destruction. It seems like a fine point to
me and there are several examples of unlucky souls who have
misjudged the point'. Of course it is possible but
I accept it is purely a matter of luck. I never made
the above statement, I did say that overstress may
cause serious damage, but flutter is much more likely
to be catastrophic.

With some gliders there is such a large margin between
placarded limits and the forces the airframe will withstand
that overstressing is definitely the lesser of 2 evils.
The Grob Acro is a perfect example of this. One of
the Acros delivered to the RAF in the UK in the 80's
was given to Slingsbys to test on a rig. After the
'normal' testing (The wing spigot problem was discovered
in this test and I was told that had this failed in
flight the airframe would probably have stayed in one
piece). Following this attempts were then made to break
the glider but despite every effort the only thing
that broke was the test rig, the glider never did.
There is no such margin for the onset of flutter. Not
all gliders have the strength of the Grob I would agreed
but there is still a margin of some sort.

The way the whole thing was explained to me was that
pulling excess G may break the glider, in particular
it may cause damage to the wing/fuselage fixing but
this damage is not necessarily total (See above re
wing spigot problem). The damage caused by flutter
is much more likely to cause total failure not only
of the wing but other aerodynamic surfaces as well
(the tailplane and fin) and a glider without a tailplane/fin
is not where I would want to be. I am told that the
weakest point on any glider is the fuselage just in
front of the fin. Again I am told that when an aircraft
breaks up in flight the cause is almost invariably
flutter, the result of overspeed, whether this is preceded
by overstress causing loss of control or not.

There has been a lot of use of words such as rubbish
and other derogatory terms. You do not have to agree
with me but I would suggest that perhaps you might
be better researching and then posting a cogent argument
why I am wrong instead of just gainsaying. (Remember
the Python :-) UK joke).

I stand by my original post, faced with the choice
of exceeding VNE or pulling too much G I would chose
the latter as the lesser of two very great evils.

Non-catastrophic may happen if you have a structure which has a plastic
behavious prior to rupture.
Ironically, you don't have that with "plastic" gliders. You might well
enconter that you can pull more g's because the designer has put lots of
margins, and nothing will happen
But if *something* happens, you're wings are simply gone on a GRP/CRP ship.
The idea that you'll get away with some sort of damage and land the ship is,
hm, fairly naive.

But to the initial question: If you are going to exceed Vne in a dive, you
can chose between putting your joker on a good spacing between Vne and
flutter speed, or put your joker on a pessimistic design margin and a well
crafted serial number. There is actually no way to tell the answer
beforehand.

But pulling the airbrakes would be fairly suicidal.

--
Bert Willing

ASW20 "TW"


"W.J. (Bill) Dean (U.K.)." a écrit dans le message
de ...
Don, I agree with you completely. You have made the points which I have
been trying to put.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Don Johnstone" wrote in
message ...

snip
The way the whole thing was explained to me was that
pulling excess G may break the glider, in particular
it may cause damage to the wing/fuselage fixing but
this damage is not necessarily total

iPilot wrote:
You may be correct. However, I have heard of some cases where there
have been structural failures resulting from excessive g-forces, but
the glider has remained landable after that. Aerobatics books also
recommend to "pull as hard as necessary", but to keep an eye on your
g-meter and ASI.

Aerobatic aircraft are built to much higher G and Vne limits, and the
pilots flying them are also accustomed to using high Gs. How many
sailplane pilots have a G meter and will be looking at it in a spin
recovery gone wrong?

High AoA eats energy rather fast. Flutter from
overspeeding will definately disintegrate your wing.

It is this claim that we are discussing. I know of many people that have
experienced flutter and not lost a wing. I also know flutter can have
many different modes, including those that involve the rudder, elevator,
ailerons, wing, and tail boom. It seems most dogmatic to claim "Flutter
from overspeeding will definitely disintegrate your wing". Since you are
so certain, perhaps you could tell us the reasons for your certainty?

Excessive-g may
not.

Has flutter caused any of the in-flight breakups discussed here? Perhaps
I missed them. I thought all were due to exceeding G limits, some likely
due to the reduced G loadings with the spoilers extended.

The trick is to stay within the limits as long as possible.
Therefore it's necessary to know the limits and their use. In
abovementioned Nimbus 4 incident it seems that pilot exchausted
g-limits before the Vne arrived. But no-one knows what really
happened.

BTW, there is one energy-burning device on every glider that may save
you the very necessary second or two - the wheel. Lower it as soon as
you feel the threat of overspeeding. You may lose the wheel doors
because of the speed and g-forces, but this is not nearly as
catastrophical as losing wing because of pulling the airbrakes at Vne
and high-g.

Does anyone have an idea of how much effect this would have? If it is
small, perhaps a pilot should not even think of attempting it as he
struggles with a recovery near Vne. In many gliders, it requires the
pilot to switch hands on the stick to lower the gear, and would be a
distraction at critical time in all of them.


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Eric Greenwell
Washington State
USA

Bert Willing wrote:

Non-catastrophic may happen if you have a structure which has a plastic
behavious prior to rupture.
Ironically, you don't have that with "plastic" gliders. You might well
enconter that you can pull more g's because the designer has put lots of
margins, and nothing will happen
But if *something* happens, you're wings are simply gone on a GRP/CRP ship.
The idea that you'll get away with some sort of damage and land the ship is,
hm, fairly naive.

But to the initial question: If you are going to exceed Vne in a dive, you
can chose between putting your joker on a good spacing between Vne and
flutter speed, or put your joker on a pessimistic design margin and a well
crafted serial number. There is actually no way to tell the answer
beforehand.

I agree with Bert. To imagine Don's advice to be suitable for all
gliders is too ignore the huge differences in design and materials. For
example, the flexible, fiberglass wing of ASW 20 probably means it has a
greater strength reserve because of the extra material needed to control
flutter, while the stiffer carbon wing in the ASW 27 might give it the
reverse margins. Consider the Standard Cirrus with it's relatively thick
fiberglass wing: where are it's margins the greatest? And, it appears
the 25 m gliders may have special problems.

Until you have discussed the design of your _particular_ glider with
it's designer, you are simply speculating about the dangers of
overspeeding versus overloading. Even the designer may not know, if the
glider hasn't been tested to flutter! And if you damage the structure
during a high G pull-up, what do you suppose will happen to the speed at
which flutter occurs? You may now have damaged glider experiencing flutter!

Fortunately, this situation seems to rare. Personally, I have never
encountered it in 4500 hours of soaring, not even an incipient spin.
Here is more speculation: I think the reality is most pilots that have
the problem will use Don's method out of reflex, not training or
conscious choice.

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Eric Greenwell
Washington State
USA