Devices for avoiding VNE?

[John Galloway]

Through the contributions to the avoiding VNE thread
runs the theme of the difficulty of avoiding overspeeding
and/or overstressing some modern designs in accidental
spin recovery. This is made more difficult than in
older composite gliders because they had a little more
drag and a little more (fortuitous) margin in the g
limits.

Is it not blindingly obvious that there is a need for
an emergency drag device that does not reduce the G
limits of gliders? Clearly if we all handled the recovery
from inadvertent spins etc perfectly all would be well
but equally clearly that does not always happen and
it is a shame to lose pilots in this situation.

As the Phoebus pilot pointed out a tail chute is ideal
for this - providing that it can be made to actuate
and jettison reliably. (I found the design used on
the Kestrel particularly good and I never once had
a failure for landing use) On the other hand they
are expensive and inconvenient to replace and there
are several ways that they can fail.

So can anyone think of a better idea than a chute?
The best I can come up with is some sort of flush
fitted rectangular-with the-long-edge-horizontal rear
hinged airbrakes (like old fashioned automobile suicide
doors) located on the fuselge sides somewhere in the
region below or below/behind the wings. If they opened
to about 45 degrees with a spring actuator (and limited
by sliding metal stays that hinge/attach to the front
of the panel and whose inner ends slid along in runners)
then they would provide a lot of drag without any deep
internal mechanism (such as wing airbrakes have).
Once they have done their job the rear end of the brakes
could be released by a spring loaded mechanism similar
to the front end so that the brakes would then instantly
spring to as position set out from and parallel to
the fuselage so that there would be very little drag
- only that provided by the stays at both ends and
the brake panels edge on to the wind. That configuration
would be good enough to fly home with. It would only
be possible to reset these brakes on the ground and
they would not replace conventional wing airbrakes
for approach control - although they could have a secondary
use for emergency approach control.

I am envisaging something the could be included in
new designs although there does not seem to be any
obvious reason why such a device could not be retrofitted
as a fairly major modification. The contours of the
brake panels would be specific to the individual fuselage
type but the mechanism could be generic. The assembly
would be fairly shallow and complete within itself
apart from e.g. a cable release attachment.

I am not advocating a technical solution to this problem
in place of spin recovery practice but I do think that
there must be something that the combined intellects
of the gliding community can come up with other than
observing that if we get into that particular overspeeding/steep
attitude condition we are stuffed.

Anyone got any simpler or better ideas? I am definitely
not an engineer.

John Galloway

[Bill Daniels]

I'd vote for the tail 'chute.

It has been approved before, it has other uses than in a near Vne incident,
the modification is relatively easy and it's light weight.

True, it's not 100% reliable but neither are the personal 'chutes we wear
yet they are deemed very useful.

Bill Daniels

"John Galloway" > wrote in message
...
> Through the contributions to the avoiding VNE thread
> runs the theme of the difficulty of avoiding overspeeding
> and/or overstressing some modern designs in accidental
> spin recovery. This is made more difficult than in
> older composite gliders because they had a little more
> drag and a little more (fortuitous) margin in the g
> limits.
>
> Is it not blindingly obvious that there is a need for
> an emergency drag device that does not reduce the G
> limits of gliders? Clearly if we all handled the recovery
> from inadvertent spins etc perfectly all would be well
> but equally clearly that does not always happen and
> it is a shame to lose pilots in this situation.
>
> As the Phoebus pilot pointed out a tail chute is ideal
> for this - providing that it can be made to actuate
> and jettison reliably. (I found the design used on
> the Kestrel particularly good and I never once had
> a failure for landing use) On the other hand they
> are expensive and inconvenient to replace and there
> are several ways that they can fail.
>
> So can anyone think of a better idea than a chute?
> The best I can come up with is some sort of flush
> fitted rectangular-with the-long-edge-horizontal rear
> hinged airbrakes (like old fashioned automobile suicide
> doors) located on the fuselge sides somewhere in the
> region below or below/behind the wings. If they opened
> to about 45 degrees with a spring actuator (and limited
> by sliding metal stays that hinge/attach to the front
> of the panel and whose inner ends slid along in runners)
> then they would provide a lot of drag without any deep
> internal mechanism (such as wing airbrakes have).
> Once they have done their job the rear end of the brakes
> could be released by a spring loaded mechanism similar
> to the front end so that the brakes would then instantly
> spring to as position set out from and parallel to
> the fuselage so that there would be very little drag
> - only that provided by the stays at both ends and
> the brake panels edge on to the wind. That configuration
> would be good enough to fly home with. It would only
> be possible to reset these brakes on the ground and
> they would not replace conventional wing airbrakes
> for approach control - although they could have a secondary
> use for emergency approach control.
>
> I am envisaging something the could be included in
> new designs although there does not seem to be any
> obvious reason why such a device could not be retrofitted
> as a fairly major modification. The contours of the
> brake panels would be specific to the individual fuselage
> type but the mechanism could be generic. The assembly
> would be fairly shallow and complete within itself
> apart from e.g. a cable release attachment.
>
> I am not advocating a technical solution to this problem
> in place of spin recovery practice but I do think that
> there must be something that the combined intellects
> of the gliding community can come up with other than
> observing that if we get into that particular overspeeding/steep
> attitude condition we are stuffed.
>
> Anyone got any simpler or better ideas? I am definitely
> not an engineer.
>
> John Galloway
>
>

[Bill Daniels]

Now I'm second thinking myself.

If the devices proposed added 20 pounds to the glider, wouldn't those same
20 pounds added as carbon fiber pultrusion rods in the spar caps increase
both the ultimate load factor and Vne enough to resolve the problem in a
better way?

Bill Daniels (again)

"Bill Daniels" > wrote in message
...
> I'd vote for the tail 'chute.
>
> It has been approved before, it has other uses than in a near Vne
incident,
> the modification is relatively easy and it's light weight.
>
> True, it's not 100% reliable but neither are the personal 'chutes we wear
> yet they are deemed very useful.
>
> Bill Daniels
>
> "John Galloway" > wrote in message
> ...
> > Through the contributions to the avoiding VNE thread
> > runs the theme of the difficulty of avoiding overspeeding
> > and/or overstressing some modern designs in accidental
> > spin recovery. This is made more difficult than in
> > older composite gliders because they had a little more
> > drag and a little more (fortuitous) margin in the g
> > limits.
> >
> > Is it not blindingly obvious that there is a need for
> > an emergency drag device that does not reduce the G
> > limits of gliders? Clearly if we all handled the recovery
> > from inadvertent spins etc perfectly all would be well
> > but equally clearly that does not always happen and
> > it is a shame to lose pilots in this situation.
> >
> > As the Phoebus pilot pointed out a tail chute is ideal
> > for this - providing that it can be made to actuate
> > and jettison reliably. (I found the design used on
> > the Kestrel particularly good and I never once had
> > a failure for landing use) On the other hand they
> > are expensive and inconvenient to replace and there
> > are several ways that they can fail.
> >
> > So can anyone think of a better idea than a chute?
> > The best I can come up with is some sort of flush
> > fitted rectangular-with the-long-edge-horizontal rear
> > hinged airbrakes (like old fashioned automobile suicide
> > doors) located on the fuselge sides somewhere in the
> > region below or below/behind the wings. If they opened
> > to about 45 degrees with a spring actuator (and limited
> > by sliding metal stays that hinge/attach to the front
> > of the panel and whose inner ends slid along in runners)
> > then they would provide a lot of drag without any deep
> > internal mechanism (such as wing airbrakes have).
> > Once they have done their job the rear end of the brakes
> > could be released by a spring loaded mechanism similar
> > to the front end so that the brakes would then instantly
> > spring to as position set out from and parallel to
> > the fuselage so that there would be very little drag
> > - only that provided by the stays at both ends and
> > the brake panels edge on to the wind. That configuration
> > would be good enough to fly home with. It would only
> > be possible to reset these brakes on the ground and
> > they would not replace conventional wing airbrakes
> > for approach control - although they could have a secondary
> > use for emergency approach control.
> >
> > I am envisaging something the could be included in
> > new designs although there does not seem to be any
> > obvious reason why such a device could not be retrofitted
> > as a fairly major modification. The contours of the
> > brake panels would be specific to the individual fuselage
> > type but the mechanism could be generic. The assembly
> > would be fairly shallow and complete within itself
> > apart from e.g. a cable release attachment.
> >
> > I am not advocating a technical solution to this problem
> > in place of spin recovery practice but I do think that
> > there must be something that the combined intellects
> > of the gliding community can come up with other than
> > observing that if we get into that particular overspeeding/steep
> > attitude condition we are stuffed.
> >
> > Anyone got any simpler or better ideas? I am definitely
> > not an engineer.
> >
> > John Galloway
> >
> >
>

[John Galloway]

As regards tail chutes - I personally would be very
happy indeed if I could get a new glider for my personal
use supplied with a tail chute and I have extolled
their virtues as emergency devices several times previously
on RAS. Unfortunately the fact is that there is a
history practical problems with reliability - especially
in club gliders and syndicates. (When I owned my own
Kestrel I took the chute home after each flight, repacked
it, and kept it in the airing cupboard to make sure
it was dry. The Kestrel also had an excellent spring
loaded actuator and a reliable mini-otfur type of release
for jettisoning. I was very confident in it.) Unfortunately
I just don't see tailchutes being put on to gliders
as emergency speed limiting devices partly because
the manufacturers would likely feel legally exposed
by the inclusion of such hit or miss, owner-maintenance-dependent
items for such a critical application.

I started to think about whether there could be a more
reliable hardware rather than fabric alternative device
tailored more towards emergency speed control than
approach control and the best I could come up with
was what was in in the last posting. BTW I don't think
that what I hand in mind would add anything like 20lbs
a pair to the glider weight.

My main motivation in starting this thread was to guage
and encourage the support for the inclusion of off-wing
emergency speed limiting devices and whatever turns
out to be the best option has my support. As gliders
get slippier and wings get thinner and design margins
get tighter and average pilot ages and reaction times
increase we either have to seek technical help or accept
that numbers over VNE accidents are going to increase.
Nothing will happen without recognition that there
is a need and customer demand for a solution.

John Galloway









At 00:24 29 March 2004, Bill Daniels wrote:
>Now I'm second thinking myself.
>
>If the devices proposed added 20 pounds to the glider,
> wouldn't those same
>20 pounds added as carbon fiber pultrusion rods in
>the spar caps increase
>both the ultimate load factor and Vne enough to resolve
>the problem in a
>better way?
>
>Bill Daniels (again)
>
>'Bill Daniels' wrote in message
...
>> I'd vote for the tail 'chute.
>>
>> It has been approved before, it has other uses than
>>in a near Vne
>incident,
>> the modification is relatively easy and it's light
>>weight.
>>
>> True, it's not 100% reliable but neither are the personal
>>'chutes we wear
>> yet they are deemed very useful.
>>
>> Bill Daniels
>>
>> 'John Galloway' wrote in message
>> ...
>> > Through the contributions to the avoiding VNE thread
>> > runs the theme of the difficulty of avoiding overspeeding
>> > and/or overstressing some modern designs in accidental
>> > spin recovery. This is made more difficult than
>>>in
>> > older composite gliders because they had a little
>>>more
>> > drag and a little more (fortuitous) margin in the
>>>g
>> > limits.
>> >
>> > Is it not blindingly obvious that there is a need
>>>for
>> > an emergency drag device that does not reduce the
>>>G
>> > limits of gliders? Clearly if we all handled the
>>>recovery
>> > from inadvertent spins etc perfectly all would be
>>>well
>> > but equally clearly that does not always happen and
>> > it is a shame to lose pilots in this situation.
>> >
>> > As the Phoebus pilot pointed out a tail chute is
>>>ideal
>> > for this - providing that it can be made to actuate
>> > and jettison reliably. (I found the design used
>>>on
>> > the Kestrel particularly good and I never once had
>> > a failure for landing use) On the other hand they
>> > are expensive and inconvenient to replace and there
>> > are several ways that they can fail.
>> >
>> > So can anyone think of a better idea than a chute?
>> > The best I can come up with is some sort of flush
>> > fitted rectangular-with the-long-edge-horizontal
>>>rear
>> > hinged airbrakes (like old fashioned automobile suicide
>> > doors) located on the fuselge sides somewhere in
>>>the
>> > region below or below/behind the wings. If they
>>>opened
>> > to about 45 degrees with a spring actuator (and limited
>> > by sliding metal stays that hinge/attach to the front
>> > of the panel and whose inner ends slid along in runners)
>> > then they would provide a lot of drag without any
>>>deep
>> > internal mechanism (such as wing airbrakes have).
>> > Once they have done their job the rear end of the
>>>brakes
>> > could be released by a spring loaded mechanism similar
>> > to the front end so that the brakes would then instantly
>> > spring to as position set out from and parallel to
>> > the fuselage so that there would be very little drag
>> > - only that provided by the stays at both ends and
>> > the brake panels edge on to the wind. That configuration
>> > would be good enough to fly home with. It would
>>>only
>> > be possible to reset these brakes on the ground and
>> > they would not replace conventional wing airbrakes
>> > for approach control - although they could have a
>>>secondary
>> > use for emergency approach control.
>> >
>> > I am envisaging something the could be included in
>> > new designs although there does not seem to be any
>> > obvious reason why such a device could not be retrofitted
>> > as a fairly major modification. The contours of
>>>the
>> > brake panels would be specific to the individual
>>>fuselage
>> > type but the mechanism could be generic. The assembly
>> > would be fairly shallow and complete within itself
>> > apart from e.g. a cable release attachment.
>> >
>> > I am not advocating a technical solution to this
>>>problem
>> > in place of spin recovery practice but I do think
>>>that
>> > there must be something that the combined intellects
>> > of the gliding community can come up with other than
>> > observing that if we get into that particular overspeeding/steep
>>>>
>> > attitude condition we are stuffed.
>> >
>> > Anyone got any simpler or better ideas? I am definitely
>> > not an engineer.
>> >
>> > John Galloway
>> >
>> >
>>
>
>

[303pilot]

Sounds like a call to go back to an earlier 15 meter design spec that
required full speed limiting device - flaps, spoilers, brakes, chute or
combination thereof.

As a 303 pilot, I'm of course partial to the trailing edge brake/flap
combination. The manual says they can be deployed up to VNE (and
pragmatically, why not even faster--what the heck you're already a test
pilot....). I've opened them and pointed the ship nearly vertical and
didn't quite reach manuevering speed. Never popped them open at at anything
above pattern speed--the manual warns of a 2g deceleration if abruptly
deployed @ VNE.

Brent


"John Galloway" > wrote in message
...
> Through the contributions to the avoiding VNE thread
> runs the theme of the difficulty of avoiding overspeeding
> and/or overstressing some modern designs in accidental
> spin recovery. This is made more difficult than in
> older composite gliders because they had a little more
> drag and a little more (fortuitous) margin in the g
> limits.
>
> Is it not blindingly obvious that there is a need for
> an emergency drag device that does not reduce the G
> limits of gliders? Clearly if we all handled the recovery
> from inadvertent spins etc perfectly all would be well
> but equally clearly that does not always happen and
> it is a shame to lose pilots in this situation.
>
> As the Phoebus pilot pointed out a tail chute is ideal
> for this - providing that it can be made to actuate
> and jettison reliably. (I found the design used on
> the Kestrel particularly good and I never once had
> a failure for landing use) On the other hand they
> are expensive and inconvenient to replace and there
> are several ways that they can fail.
>
> So can anyone think of a better idea than a chute?
> The best I can come up with is some sort of flush
> fitted rectangular-with the-long-edge-horizontal rear
> hinged airbrakes (like old fashioned automobile suicide
> doors) located on the fuselge sides somewhere in the
> region below or below/behind the wings. If they opened
> to about 45 degrees with a spring actuator (and limited
> by sliding metal stays that hinge/attach to the front
> of the panel and whose inner ends slid along in runners)
> then they would provide a lot of drag without any deep
> internal mechanism (such as wing airbrakes have).
> Once they have done their job the rear end of the brakes
> could be released by a spring loaded mechanism similar
> to the front end so that the brakes would then instantly
> spring to as position set out from and parallel to
> the fuselage so that there would be very little drag
> - only that provided by the stays at both ends and
> the brake panels edge on to the wind. That configuration
> would be good enough to fly home with. It would only
> be possible to reset these brakes on the ground and
> they would not replace conventional wing airbrakes
> for approach control - although they could have a secondary
> use for emergency approach control.
>
> I am envisaging something the could be included in
> new designs although there does not seem to be any
> obvious reason why such a device could not be retrofitted
> as a fairly major modification. The contours of the
> brake panels would be specific to the individual fuselage
> type but the mechanism could be generic. The assembly
> would be fairly shallow and complete within itself
> apart from e.g. a cable release attachment.
>
> I am not advocating a technical solution to this problem
> in place of spin recovery practice but I do think that
> there must be something that the combined intellects
> of the gliding community can come up with other than
> observing that if we get into that particular overspeeding/steep
> attitude condition we are stuffed.
>
> Anyone got any simpler or better ideas? I am definitely
> not an engineer.
>
> John Galloway
>
>

[Andreas Maurer]

On 28 Mar 2004 22:53:07 GMT, John Galloway
> wrote:

>Through the contributions to the avoiding VNE thread
>runs the theme of the difficulty of avoiding overspeeding
>and/or overstressing some modern designs in accidental
>spin recovery. This is made more difficult than in
>older composite gliders because they had a little more
>drag and a little more (fortuitous) margin in the g
>limits.
>
>Is it not blindingly obvious that there is a need for
>an emergency drag device that does not reduce the G
>limits of gliders? Clearly if we all handled the recovery
>from inadvertent spins etc perfectly all would be well
>but equally clearly that does not always happen and
>it is a shame to lose pilots in this situation.

Well, I have to admit that as fine as your solution sounds - it will
only be the cure for an extremely small part of all glider accidents.

How big is the fraction of overspeed/overG accidents after a spin
recovery that went wrong? 0.1 percent? 0.2 percent?

Certainly not higher - the only inflight breakups in such a situation
I ever heard of were the ASW-22 prototype (1981), the eta and the US
Nimbus, the first two being test flights of prototypes.

In the 22 case it was clear that the airframe would break up before
the flight beacuse it was not designed for the load factors that were
created by extreme asymmetrical water ballast load.

Bert Willing also exceeded the design limits of a 26 meter glider, but
his glider survived the incident without damage.


Investing a very small part of the costs for such a device in, say,
three spin-training flights per year, is probably going to make things
a lot safer.

I think the money is far better invested in a rescue system, be it
NOAH, bei it Soteira (which I prefer), or be it a BRS. A rescue system
will be able to safe the pilot in a lot more cases than a strong
airbrake.



Bye
Andreas

[W.J. \(Bill\) Dean \(U.K.\).]

There was also the U.K. based Nimbus 4 in Spain.

The ASW20CL on 11th January 1987 was an overspeed accident. It did not
break up, control was lost and it hit the ground at very high speed.

I should have thought there was a case for an optional tail chute on
machines such as the big Nimbus and perhaps the Duo Discus, it was fitted to
the Janus and the Nimbus 2.

The ASW17 was available with a belly chute.

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

>
> "Andreas Maurer" > wrote in message
> ...
>
> >
> > On 28 Mar 2004 22:53:07 GMT, John Galloway
> > > wrote:
> >
> >Through the contributions to the avoiding VNE thread
> >runs the theme of the difficulty of avoiding overspeeding
> >and/or overstressing some modern designs in accidental
> >spin recovery. This is made more difficult than in
> >older composite gliders because they had a little more
> >drag and a little more (fortuitous) margin in the g
> >limits.
> >
> >Is it not blindingly obvious that there is a need for
> >an emergency drag device that does not reduce the G
> >limits of gliders? Clearly if we all handled the recovery
> >from inadvertent spins etc perfectly all would be well
> >but equally clearly that does not always happen and
> >it is a shame to lose pilots in this situation.
>
> Well, I have to admit that as fine as your solution sounds - it will
> only be the cure for an extremely small part of all glider accidents.
>
> How big is the fraction of overspeed/overG accidents after a spin
> recovery that went wrong? 0.1 percent? 0.2 percent?
>
> Certainly not higher - the only inflight breakups in such a situation
> I ever heard of were the ASW-22 prototype (1981), the eta and the US
> Nimbus, the first two being test flights of prototypes.
>
> In the 22 case it was clear that the airframe would break up before
> the flight because it was not designed for the load factors that were
> created by extreme asymmetrical water ballast load.
>
> Bert Willing also exceeded the design limits of a 26 meter glider, but
> his glider survived the incident without damage.
>
>
> Investing a very small part of the costs for such a device in, say,
> three spin-training flights per year, is probably going to make things
> a lot safer.
>
> I think the money is far better invested in a rescue system, be it
> NOAH, bee it Soteira (which I prefer), or be it a BRS. A rescue system
> will be able to safe the pilot in a lot more cases than a strong
> airbrake.
>
> Bye
> Andreas
>

[Andreas Maurer]

On Mon, 29 Mar 2004 23:50:20 +0100, "W.J. \(Bill\) Dean \(U.K.\)."
> wrote:

>There was also the U.K. based Nimbus 4 in Spain.

This makes it 4 accidents in the last 23 years. ;)


>The ASW20CL on 11th January 1987 was an overspeed accident. It did not
>break up, control was lost and it hit the ground at very high speed.

Interesting case - is there a detailed rport available online?


>I should have thought there was a case for an optional tail chute on
>machines such as the big Nimbus and perhaps the Duo Discus, it was fitted to
>the Janus and the Nimbus 2.
>
>The ASW17 was available with a belly chute.

I agree 100% - a tail chute (or better a belly chute) might be a good
idea.
I would not regard it as a primary Vne-avoidance device, but rather a
useful help to keep the speed down after an inflight breakup (e-g.
after a collision with loss of wing or tail), giving the pilot more
time to get out and maybe even stabilizing the falling wreckage.


Bye
Andreas

[W.J. \(Bill\) Dean \(U.K.\).]

I am afraid not.

I do not know whether this accident was investigated direct by the AAIB or
whether it was delegated to the BGA, but in either case U.K. accidents as
far back as that are not on-line.

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

>
> "Andreas Maurer" > wrote in message
> ...
>
> >
> > On Mon, 29 Mar 2004 23:50:20 +0100, "W.J. \(Bill\) Dean \(U.K.\)."
> > > wrote:
> >
> > <snip>
> >
> > The ASW20CL on 11th January 1987 was an overspeed accident. It did not
> > break up, control was lost and it hit the ground at very high speed.
> >
> > <snip>
> >
>
> Interesting case - is there a detailed rport available online?
>
> Bye
> Andreas
>

[Edward Downham]

>Subject: Re: Devices for avoiding VNE?
>From: "W.J. \(Bill\) Dean \(U.K.\)."
>Date: 30/03/2004 10:15 GMT Standard Time
>Message-id: >
>
>I am afraid not.
>
>I do not know whether this accident was investigated direct by the AAIB or
>whether it was delegated to the BGA, but in either case U.K. accidents as
>far back as that are not on-line.
>
>W.J. (Bill) Dean (U.K.).
>Remove "ic" to reply.
>
>>
>> "Andreas Maurer" > wrote in message
>> ...
>>
>> >
>> > On Mon, 29 Mar 2004 23:50:20 +0100, "W.J. \(Bill\) Dean \(U.K.\)."
>> > > wrote:
>> >
>> > <snip>
>> >
>> > The ASW20CL on 11th January 1987 was an overspeed accident. It did not
>> > break up, control was lost and it hit the ground at very high speed.
>> >
>> > <snip>
>> >
>>
>> Interesting case - is there a detailed rport available online?
>>
>> Bye
>> Andreas
>>
>
>
>

I don't know if this accident was the subject of a _formal_ AAIB investigation;
I do know that one of their guys spent some time with the wreckage and talking
to Schleicher, amongst others.

From what I remember (I was at the airfield the day this happened but didn't
witness the crash) the glider was observed to be hillsoaring and climbing in
weak thermals near the site. Eyewitness say it departed from level flight (in
what way I'm not sure) then went into a steepening dive from which it did not
recover. The height it started the dive from was estimated at 1200-1600', which
ties in with the speed it hit the ground.

I don't remember if there was ever a 'probable cause' given but several factors
were quoted post-investigation:

a) The pilot was new to type and fairly inexperienced (in gliders).
b) She was of quite light build.
c) She was an experienced hang-glider pilot.
d) The glider was being flown in comps. by another syndicate member and had
been ballasted in the tail to take it close to the aft CG limit (when flown by
her partner).

There is/was plenty of fuel for the speculative fire but I don't think we'll
ever know exactly why this happened...

P.S. I think it was actually a ASW-20_B_L, not that it makes an incredible
difference.

[Mackfly]

>From: John Galloway
>Date: 3/28/2004 4:53 PM Central Standard Time

>Through the contributions to the avoiding VNE thread
>runs the theme of the difficulty of avoiding overspeeding
>and/or overstressing some modern designs in accidental
>spin recovery. This is made more difficult than in
>older composite gliders because they had a little more
>drag and a little more (fortuitous) margin in the g limits.
etc. etc.
Ok john here we go---get a JATO bottle and mount it backwards in the nose.
Secondary uses. Glider release fails---torch that tow rope! Also very short
roll outs for them off airport landouts.
Along your thoughts for a fuselage mounted air brake--how about two chutes
about two foot in diameter each that would, when inflated, rest a little foward
of the wing T.E. and along side the fuselage. Like a "pilot" chute sorta
thingy deal. They could be released after the, to fast dive, had been
recovered or flown on in to a landing were you close enough to the airport.
Being close to the center line would be a plus if one should fail to open. The
canopy of the chute could even be attached to the fuselage to keep the little
buggers from beating around. You could pop them out of an aft and outward
facing oval ended surface flush tube and leave the "oval cover plate" on the
fabric of the chute. Hmmm--- The lanyard and everything could pack in the
tube. Pop it out with a coil spring.
Ok-- everybody saw it here first. John send me a check for 15% of the
profit on each of these you sell in the future. Now if I'd just get busy and
try this out on that 16 foot span RC motorglider I have hanging in the
basement. mac--- inventor--thinker--under paid

[Arnold Pieper]

John,

The airbrakes were designed not only to be used for approach and landing,
but also to avoid reaching VNE.
Look at your glider's POH and check what is the maximum speed to deploy the
airbrakes, and what becomes the VNE with them deployed.

In most modern design gliders, the airbrakes can be deployed up to VNE, and
they will prevent the glider from reaching VNE when fully opened.

The airbrakes are designed for this purpose.

Once the airbrakes are opened and will prevent you from going over VNE,
there's no need to pull at anything even close to the design limit G.

Spin training therefore, is the best way to ease this fear and learn how to
pull without overstressing the airframe.

AP


"John Galloway" > wrote in message
...
> Through the contributions to the avoiding VNE thread
> runs the theme of the difficulty of avoiding overspeeding
> and/or overstressing some modern designs in accidental
> spin recovery. This is made more difficult than in
> older composite gliders because they had a little more
> drag and a little more (fortuitous) margin in the g
> limits.
>
> Is it not blindingly obvious that there is a need for
> an emergency drag device that does not reduce the G
> limits of gliders? Clearly if we all handled the recovery
> from inadvertent spins etc perfectly all would be well
> but equally clearly that does not always happen and
> it is a shame to lose pilots in this situation.
>
> As the Phoebus pilot pointed out a tail chute is ideal
> for this - providing that it can be made to actuate
> and jettison reliably. (I found the design used on
> the Kestrel particularly good and I never once had
> a failure for landing use) On the other hand they
> are expensive and inconvenient to replace and there
> are several ways that they can fail.
>
> So can anyone think of a better idea than a chute?
> The best I can come up with is some sort of flush
> fitted rectangular-with the-long-edge-horizontal rear
> hinged airbrakes (like old fashioned automobile suicide
> doors) located on the fuselge sides somewhere in the
> region below or below/behind the wings. If they opened
> to about 45 degrees with a spring actuator (and limited
> by sliding metal stays that hinge/attach to the front
> of the panel and whose inner ends slid along in runners)
> then they would provide a lot of drag without any deep
> internal mechanism (such as wing airbrakes have).
> Once they have done their job the rear end of the brakes
> could be released by a spring loaded mechanism similar
> to the front end so that the brakes would then instantly
> spring to as position set out from and parallel to
> the fuselage so that there would be very little drag
> - only that provided by the stays at both ends and
> the brake panels edge on to the wind. That configuration
> would be good enough to fly home with. It would only
> be possible to reset these brakes on the ground and
> they would not replace conventional wing airbrakes
> for approach control - although they could have a secondary
> use for emergency approach control.
>
> I am envisaging something the could be included in
> new designs although there does not seem to be any
> obvious reason why such a device could not be retrofitted
> as a fairly major modification. The contours of the
> brake panels would be specific to the individual fuselage
> type but the mechanism could be generic. The assembly
> would be fairly shallow and complete within itself
> apart from e.g. a cable release attachment.
>
> I am not advocating a technical solution to this problem
> in place of spin recovery practice but I do think that
> there must be something that the combined intellects
> of the gliding community can come up with other than
> observing that if we get into that particular overspeeding/steep
> attitude condition we are stuffed.
>
> Anyone got any simpler or better ideas? I am definitely
> not an engineer.
>
> John Galloway
>
>

[W.J. \(Bill\) Dean \(U.K.\).]

NO. This is thoroughly misleading.

HISTORICAL.

When the first gliders with good (for the day) performance were built,
it was found that the good performance made them difficult to land.

So they were fitted with spoilers as a landing aid.

Then pilots started to cloud fly, and some lost control in cloud
and overspeeded and overstressed their gliders, which broke up.

This was countered by developing and fitting speed-limiting airbrakes
(DFS, e.g. Weihe and Slingsby Sky, and Schempp-Hirth). These were intended
to be speed limiting in a true vertical dive.

In the U.K. it was a requirement that the glider was test flown to prove
that at max. all up weight in a vertical dive Vne was not exceeded,
I understand that the Slingsby Skylark series all passed this test.

Note that max. manoeuvring and rough air speeds WOULD be exceeded.

Later, it was found that with higher wing loadings, thinner wing sections
and higher aspect ratios it became practically impossible to fit true speed
limiting brakes (in the sense that Vne would not be exceeded in a true
vertical dive at max. a.u.w.). The first U.K. built gliders for which this
applied were, I believe, some at least of the Slingsby Dart series.

Also, if the rules were relaxed life would become a lot easier for the
designer, because it would save weight and cost. So the rules were
relaxed, and "Speed limiting" came to mean "In a dive at X degrees", usually
I understand of 45 degrees.

TODAY

Most gliders today, including I believe all those built in Europe, are
designed to JAR 22.

See:
Joint Aviation Authorities, Europe. http://www.jaa.nl/ ,
JARs – Section 1 – JAR-22 http://www.jaa.nl/section1/jars/445499.pdf .

The relevant clause is:

"JAR 22.73 Descent, high speed

"It must be shown that the sailplane with the airbrakes extended, will not
exceed VNE in a dive at an angle to the horizon of:

"(a) 45° when the sailplane is approved for cloud flying and/or aerobatics
when certificated in the Aerobatic or Utility Category;

"(b) 30° in other cases.

"[Ch. 5, 28.10.95]"

Some modern gliders, including some being built today, probably still have
true speed limiting brakes by the strict old definition given above; my
guess is that these would all be gliders with trailing edge brakes or
braking flaps such as the early Pik 20; but this would not necessarily be
true for all gliders with such brakes.

Some gliders were built with tailchutes, either in an attempt to comply with
the old strict requirement, or because it was necessary if they were to
comply with the relaxed rule. I have always understood that the Janus was
fitted with a tailchute to be speed limiting in a 45 degree dive at max.
a.u.w. with full water ballast.

At what dive angle would a Duo-Discus with full brakes go through Vne?
I would be astonished if this is more than 45 degrees, it may very well be
30 degrees.

So if in a spin recovery, or for any other reason, you are diving at a very
steep angle your air-brakes are unlikely to save you from exceeding Vne.
I am sure they won't in the Nimbus 3/4 series; it was not a requirement for
certification.

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

>
> "Arnold Pieper" > wrote in message
> . com...
>
> John,
>
> The airbrakes were designed not only to be used for approach and landing,
> but also to avoid reaching VNE.
>
> Look at your glider's POH and check what is the maximum speed to deploy
> the airbrakes, and what becomes the VNE with them deployed.
>
> In most modern design gliders, the airbrakes can be deployed up to VNE,
> and they will prevent the glider from reaching VNE when fully opened.
>
> The airbrakes are designed for this purpose.
>
> Once the airbrakes are opened and will prevent you from going over VNE,
> there's no need to pull at anything even close to the design limit G.
>
> Spin training therefore, is the best way to ease this fear and learn how
> to pull without overstressing the airframe.
>
> AP
>
> >
> > "John Galloway" > wrote in message
> > ...
> >
> > Through the contributions to the avoiding VNE thread
> > runs the theme of the difficulty of avoiding overspeeding
> > and/or overstressing some modern designs in accidental
> > spin recovery. This is made more difficult than in
> > older composite gliders because they had a little more
> > drag and a little more (fortuitous) margin in the g
> > limits.
> >
> > Is it not blindingly obvious that there is a need for
> > an emergency drag device that does not reduce the G
> > limits of gliders? Clearly if we all handled the recovery
> > from inadvertent spins etc perfectly all would be well
> > but equally clearly that does not always happen and
> > it is a shame to lose pilots in this situation.
> >
> > As the Phoebus pilot pointed out a tail chute is ideal
> > for this - providing that it can be made to actuate
> > and jettison reliably. (I found the design used on
> > the Kestrel particularly good and I never once had
> > a failure for landing use.) On the other hand they
> > are expensive and inconvenient to replace and there
> > are several ways that they can fail.
> >
> > So can anyone think of a better idea than a chute?
> > The best I can come up with is some sort of flush
> > fitted rectangular-with the-long-edge-horizontal rear
> > hinged airbrakes (like old fashioned automobile suicide
> > doors) located on the fuselage sides somewhere in the
> > region below or below/behind the wings. If they opened
> > to about 45 degrees with a spring actuator (and limited
> > by sliding metal stays that hinge/attach to the front
> > of the panel and whose inner ends slid along in runners)
> > then they would provide a lot of drag without any deep
> > internal mechanism (such as wing airbrakes have).
> > Once they have done their job the rear end of the brakes
> > could be released by a spring loaded mechanism similar
> > to the front end so that the brakes would then instantly
> > spring to as position set out from and parallel to
> > the fuselage so that there would be very little drag
> > - only that provided by the stays at both ends and
> > the brake panels edge on to the wind. That configuration
> > would be good enough to fly home with. It would only
> > be possible to reset these brakes on the ground and
> > they would not replace conventional wing airbrakes
> > for approach control - although they could have a secondary
> > use for emergency approach control.
> >
> > I am envisaging something the could be included in
> > new designs although there does not seem to be any
> > obvious reason why such a device could not be retrofitted
> > as a fairly major modification. The contours of the
> > brake panels would be specific to the individual fuselage
> > type but the mechanism could be generic. The assembly
> > would be fairly shallow and complete within itself
> > apart from e.g. a cable release attachment.
> >
> > I am not advocating a technical solution to this problem
> > in place of spin recovery practice but I do think that
> > there must be something that the combined intellects
> > of the gliding community can come up with other than
> > observing that if we get into that particular overspeeding/steep
> > attitude condition we are stuffed.
> >
> > Anyone got any simpler or better ideas? I am definitely
> > not an engineer.
> >
> > John Galloway
> >
>

[John Galloway]

Thanks Bill.

You detail the historical background to the paradox
implicit in the 'Avoiding VNE' thread that a glider
can be, at one and the same time, both technically
within its operating limits, and also in an irrecoverable
situation - i.e. if it is flying in a fast, accelerating,
steep angle configuration (leaving those as vague terms
as the values will vary between types) - even assumming
a hypothetical empty airmass of infinite size and zero
turbulence.

This is a bit unfortunate for those who find themselves
in that situation and I think that it would be nice
if gliders that are within their limits had the capability
of not exceeding them if it is technically possible.

John Galloway


At 15:18 31 March 2004, W.J. \bill\ Dean \u.K.\. wrote:
>NO. This is thoroughly misleading.
>
>HISTORICAL.
>
>When the first gliders with good (for the day) performance
>were built,
>it was found that the good performance made them difficult
>to land.
>
>So they were fitted with spoilers as a landing aid.
>
>Then pilots started to cloud fly, and some lost control
>in cloud
>and overspeeded and overstressed their gliders, which
>broke up.
>
>This was countered by developing and fitting speed-limiting
>airbrakes
>(DFS, e.g. Weihe and Slingsby Sky, and Schempp-Hirth).
> These were intended
>to be speed limiting in a true vertical dive.
>
>In the U.K. it was a requirement that the glider was
>test flown to prove
>that at max. all up weight in a vertical dive Vne was
>not exceeded,
>I understand that the Slingsby Skylark series all passed
>this test.
>
>Note that max. manoeuvring and rough air speeds WOULD
>be exceeded.
>
>Later, it was found that with higher wing loadings,
>thinner wing sections
>and higher aspect ratios it became practically impossible
>to fit true speed
>limiting brakes (in the sense that Vne would not be
>exceeded in a true
>vertical dive at max. a.u.w.). The first U.K. built
>gliders for which this
>applied were, I believe, some at least of the Slingsby
>Dart series.
>
>Also, if the rules were relaxed life would become a
>lot easier for the
>designer, because it would save weight and cost.
>So the rules were
>relaxed, and 'Speed limiting' came to mean 'In a dive
>at X degrees', usually
>I understand of 45 degrees.
>
>TODAY
>
>Most gliders today, including I believe all those built
>in Europe, are
>designed to JAR 22.
>
>See:
>Joint Aviation Authorities, Europe. http://www.jaa.nl/
>,
>JARs – Section 1 – JAR-22 http://www.jaa.nl/section1/jars/445499.
>>pdf .
>
>The relevant clause is:
>
>'JAR 22.73 Descent, high speed
>
>'It must be shown that the sailplane with the airbrakes
>extended, will not
>exceed VNE in a dive at an angle to the horizon of:
>
>'(a) 45° when the sailplane is approved for cloud flying
>and/or aerobatics
>when certificated in the Aerobatic or Utility Category;
>
>'(b) 30° in other cases.
>
>'[Ch. 5, 28.10.95]'
>
>Some modern gliders, including some being built today,
>probably still have
>true speed limiting brakes by the strict old definition
>given above; my
>guess is that these would all be gliders with trailing
>edge brakes or
>braking flaps such as the early Pik 20; but this would
>not necessarily be
>true for all gliders with such brakes.
>
>Some gliders were built with tailchutes, either in
>an attempt to comply with
>the old strict requirement, or because it was necessary
>if they were to
>comply with the relaxed rule. I have always understood
>that the Janus was
>fitted with a tailchute to be speed limiting in a 45
>degree dive at max.
>a.u.w. with full water ballast.
>
>At what dive angle would a Duo-Discus with full brakes
>go through Vne?
>I would be astonished if this is more than 45 degrees,
>it may very well be
>30 degrees.
>
>So if in a spin recovery, or for any other reason,
>you are diving at a very
>steep angle your air-brakes are unlikely to save you
>from exceeding Vne.
>I am sure they won't in the Nimbus 3/4 series; it was
>not a requirement for
>certification.
>
>W.J. (Bill) Dean (U.K.).
>Remove 'ic' to reply.
>
>>
>> 'Arnold Pieper' wrote in message
>> . com...
>>
>> John,
>>
>> The airbrakes were designed not only to be used for
>>approach and landing,
>> but also to avoid reaching VNE.
>>
>> Look at your glider's POH and check what is the maximum
>>speed to deploy
>> the airbrakes, and what becomes the VNE with them
>>deployed.
>>
>> In most modern design gliders, the airbrakes can be
>>deployed up to VNE,
>> and they will prevent the glider from reaching VNE
>>when fully opened.
>>
>> The airbrakes are designed for this purpose.
>>
>> Once the airbrakes are opened and will prevent you
>>from going over VNE,
>> there's no need to pull at anything even close to
>>the design limit G.
>>
>> Spin training therefore, is the best way to ease this
>>fear and learn how
>> to pull without overstressing the airframe.
>>
>> AP
>>
>> >
>> > 'John Galloway' wrote in message
>> > ...
>> >
>> > Through the contributions to the avoiding VNE thread
>> > runs the theme of the difficulty of avoiding overspeeding
>> > and/or overstressing some modern designs in accidental
>> > spin recovery. This is made more difficult than
>>>in
>> > older composite gliders because they had a little
>>>more
>> > drag and a little more (fortuitous) margin in the
>>>g
>> > limits.
>> >
>> > Is it not blindingly obvious that there is a need
>>>for
>> > an emergency drag device that does not reduce the
>>>G
>> > limits of gliders? Clearly if we all handled the
>>>recovery
>> > from inadvertent spins etc perfectly all would be
>>>well
>> > but equally clearly that does not always happen and
>> > it is a shame to lose pilots in this situation.
>> >
>> > As the Phoebus pilot pointed out a tail chute is
>>>ideal
>> > for this - providing that it can be made to actuate
>> > and jettison reliably. (I found the design used
>>>on
>> > the Kestrel particularly good and I never once had
>> > a failure for landing use.) On the other hand they
>> > are expensive and inconvenient to replace and there
>> > are several ways that they can fail.
>> >
>> > So can anyone think of a better idea than a chute?
>> > The best I can come up with is some sort of flush
>> > fitted rectangular-with the-long-edge-horizontal
>>>rear
>> > hinged airbrakes (like old fashioned automobile suicide
>> > doors) located on the fuselage sides somewhere in
>>>the
>> > region below or below/behind the wings. If they
>>>opened
>> > to about 45 degrees with a spring actuator (and limited
>> > by sliding metal stays that hinge/attach to the front
>> > of the panel and whose inner ends slid along in runners)
>> > then they would provide a lot of drag without any
>>>deep
>> > internal mechanism (such as wing airbrakes have).
>> > Once they have done their job the rear end of the
>>>brakes
>> > could be released by a spring loaded mechanism similar
>> > to the front end so that the brakes would then instantly
>> > spring to as position set out from and parallel to
>> > the fuselage so that there would be very little drag
>> > - only that provided by the stays at both ends and
>> > the brake panels edge on to the wind. That configuration
>> > would be good enough to fly home with. It would
>>>only
>> > be possible to reset these brakes on the ground and
>> > they would not replace conventional wing airbrakes
>> > for approach control - although they could have a
>>>secondary
>> > use for emergency approach control.
>> >
>> > I am envisaging something the could be included in
>> > new designs although there does not seem to be any
>> > obvious reason why such a device could not be retrofitted
>> > as a fairly major modification. The contours of
>>>the
>> > brake panels would be specific to the individual
>>>fuselage
>> > type but the mechanism could be generic. The assembly
>> > would be fairly shallow and complete within itself
>> > apart from e.g. a cable release attachment.
>> >
>> > I am not advocating a technical solution to this
>>>problem
>> > in place of spin recovery practice but I do think
>>>that
>> > there must be something that the combined intellects
>> > of the gliding community can come up with other than
>> > observing that if we get into that particular overspeeding/steep
>>>>
>> > attitude condition we are stuffed.
>> >
>> > Anyone got any simpler or better ideas? I am definitely
>> > not an engineer.
>> >
>> > John Galloway
>> >
>>
>
>
>
>

[Eric Greenwell]

John Galloway wrote:
> Thanks Bill.
>
> You detail the historical background to the paradox
> implicit in the 'Avoiding VNE' thread that a glider
> can be, at one and the same time, both technically
> within its operating limits, and also in an irrecoverable
> situation - i.e. if it is flying in a fast, accelerating,
> steep angle configuration (leaving those as vague terms
> as the values will vary between types) - even assumming
> a hypothetical empty airmass of infinite size and zero
> turbulence.
>
> This is a bit unfortunate for those who find themselves
> in that situation and I think that it would be nice
> if gliders that are within their limits had the capability
> of not exceeding them if it is technically possible.

It would be nice, and it is technically possible, but perhaps not
economically viable, judging by the number of manufacturer that offer
them. "Speed-limiting" gliders are available; for example, the Ka-6E and
other gliders designed to the speed-limiting standards, and gliders with
trailing edge dive brakes.

Personally, I think other things are more likely to kill me, so I would
prefer money and research effort be spent on more crash-tolerant
cockpits, pilot rescue systems, spin resistance, spoilers and canopies
that won't open when left unlocked, and simpler, more reliable
self-launching systems.
--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Denis]

Todd Pattist wrote:

>>The airbrakes are designed for this purpose.
>
> Not in any modern glider I know of. Anywhere close to
> vertical will exceed Vne with the brakes open.

The elevator is designed for that purpose (getting out of the vertical
cone where a glider will exceed VNE with airbrakes) ;-)

--
Denis

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

[Denis]

John Galloway wrote:

> This is a bit unfortunate for those who find themselves
> in that situation and I think that it would be nice
> if gliders that are within their limits had the capability
> of not exceeding them if it is technically possible.

You're right but it's the pilot task to think ahead and not to fall into
such a situation. You cannot achieve high performance in a pilot-proof
glider...

The same when you are flying above unlandable terrain, there is nothing
illegal in this but you are in a great risk. And you have to think ahead
and stay within reach of a landing field...


--
Denis

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

[Arnold Pieper]

It


"Todd Pattist" > wrote in message
...
> "Arnold Pieper" > wrote:
>
> >In most modern design gliders, the airbrakes can be deployed up to VNE,
and
> >they will prevent the glider from reaching VNE when fully opened.
> >
> >The airbrakes are designed for this purpose.
>
> Not in any modern glider I know of. Anywhere close to
> vertical will exceed Vne with the brakes open.
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

[Arnold Pieper]

Maybe true if "near vertical", however, staying at a near vertical dive is
something that requires a conscient effort.
The glider won't just stay there on its own.
To remain in a 90 degree vertical dive requires a significant amount of
forward stick force and concentration.
As speed increases, the nose will come up (away from vertical) even if you
don't want it to, and even with full forward trim, it would still require an
honest push on the stick to maintain that attitude.

If you're recovering from an unusual attitude that puts you in a near
vertical dive, just don't sweat it.
Open the airbrakes and slowly pull out of the dive. There is no need to
overstress.

If you want to feel safer, go for aerobatic training.
You will see that you can actually dive 90 degrees down and recover without
exceeding VNE, without using the airbrakes and not getting even close to G
limits.
Even if you lag behind the glider and airspeed gets close to VNE, just open
the airbrakes and do a gentle pull out.




"Todd Pattist" > wrote in message
...
> "Arnold Pieper" > wrote:
>
> >In most modern design gliders, the airbrakes can be deployed up to VNE,
and
> >they will prevent the glider from reaching VNE when fully opened.
> >
> >The airbrakes are designed for this purpose.
>
> Not in any modern glider I know of. Anywhere close to
> vertical will exceed Vne with the brakes open.
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

[Arnold Pieper]

The glider won't stay at 90 degrees nose down like I said. As it accelerate
it will bring the nose up.
That in itself is no guarantee you won't reach VNE before long, of course,
so you have to control the recovery.
Avoid reaching VNE by deploying the airbrakes if you see the speed
increasing too fast, as I said, controlling the dive.
That is always better than trying to bend the wings by pulling too many Gs.
Your attitude will be at 45 degrees or less in a matter of seconds, and at
that attitude, the airbrakes will prevent the overspeed or at least minimize
the condition (if they were deployed too late).

You can go over VNE if you don't deploy the airbrakes and just try to
"G-load" your way out of such a high-speed dive,and that's the condition in
which you overstress the structure, produce internal cracks, bend or damage
some of the hardware in the control system.
That's the reason you should watch the airspeed and deploy the airbrakes in
time (before reaching VNE).

Don't be affraid to open the airbrakes at high speed, believe me, the
manufacturer is just a little smarter than that.
You have to be careful at high speed just because they tend to jump out more
easily, so, have a firm hand on it.

Real aerobatic training (as opposed to some occasional loops) will clarify a
lot of this.


"Todd Pattist" > wrote in message
...
> "Arnold Pieper" > wrote:
>
> >Maybe true if "near vertical", however, staying at a near vertical dive
is
> >something that requires a conscient effort.
> >The glider won't just stay there on its own.
> >To remain in a 90 degree vertical dive requires a significant amount of
> >forward stick force and concentration.
> >As speed increases, the nose will come up (away from vertical) even if
you
> >don't want it to, and even with full forward trim, it would still require
an
> >honest push on the stick to maintain that attitude.
>
> All of this is true, but it's not relevant to whether the
> airbrakes of a modern glider are speed limiting. They
> aren't. There are lots of initial conditions that will
> exceed Vne with the brakes out.
>
> >If you're recovering from an unusual attitude that puts you in a near
> >vertical dive, just don't sweat it.
> >Open the airbrakes and slowly pull out of the dive. There is no need to
> >overstress.
>
> There is also no guarantee that you will not exceed Vne or
> that your final speed will be lower than someone who applies
> a higher AOA with it's higher G-load and reduces the descent
> angle more quickly.
>
> >If you want to feel safer, go for aerobatic training.
> >You will see that you can actually dive 90 degrees down and recover
without
> >exceeding VNE, without using the airbrakes and not getting even close to
G
> >limits.
>
> I do loops often. Slow and vertical is far different from
> fast and vertical.
>
>
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

[Mark Navarre]

>From: "Arnold Pieper"
>Date: 3/31/2004 1:16 PM Pacific Standard Time
>Message-id: >

>Maybe true if "near vertical", however, staying at a near vertical dive is
>something that requires a conscient effort.
>The glider won't just stay there on its own.
>To remain in a 90 degree vertical dive requires a significant amount of
>forward stick force and concentration.
>As speed increases, the nose will come up (away from vertical) even if you
>don't want it to, and even with full forward trim, it would still require an
>honest push on the stick to maintain that attitude.

Not true with all gliders. Several modern racing ships will, when trimmed
within CG limits for best climb performance, "tuck" or pitch down with
increasing airspeed, resulting in a large outside loop or exceeding VNE without
pilot input. The crossover speed for this in my own ship is about 115 kts,
above which slight back pressure is needed to maintain speed.

-
Mark Navarre
2/5 black ace
LoCal, USA
-

[Eric Greenwell]

Mark Navarre wrote:

>>As speed increases, the nose will come up (away from vertical) even if you
>>don't want it to, and even with full forward trim, it would still require an
>>honest push on the stick to maintain that attitude.
>
>
> Not true with all gliders. Several modern racing ships will, when trimmed
> within CG limits for best climb performance, "tuck" or pitch down with
> increasing airspeed, resulting in a large outside loop or exceeding VNE without
> pilot input. The crossover speed for this in my own ship is about 115 kts,
> above which slight back pressure is needed to maintain speed.

Which glider is that? I thought a pitch-up tendency with increasing
speed was a certification requirement? And what is the CG position for
this to happen? Is this "feature" mentioned in the flight manaul? Sounds
kind of scary.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Chris Rollings]

Nimbus 3 and 4 and Duo Discus brakes do not meet the
'speed limiting in a 45 degree dive' requirement, but
do achieve that in a 30 degree dive. That's why they
are non-aerobatic.

At 15:18 31 March 2004, W.J. \bill\ Dean \u.K.\. wrote:
>NO. This is thoroughly misleading.
>
>HISTORICAL.
>
>When the first gliders with good (for the day) performance
>were built,
>it was found that the good performance made them difficult
>to land.
>
>So they were fitted with spoilers as a landing aid.
>
>Then pilots started to cloud fly, and some lost control
>in cloud
>and overspeeded and overstressed their gliders, which
>broke up.
>
>This was countered by developing and fitting speed-limiting
>airbrakes
>(DFS, e.g. Weihe and Slingsby Sky, and Schempp-Hirth).
> These were intended
>to be speed limiting in a true vertical dive.
>
>In the U.K. it was a requirement that the glider was
>test flown to prove
>that at max. all up weight in a vertical dive Vne was
>not exceeded,
>I understand that the Slingsby Skylark series all passed
>this test.
>
>Note that max. manoeuvring and rough air speeds WOULD
>be exceeded.
>
>Later, it was found that with higher wing loadings,
>thinner wing sections
>and higher aspect ratios it became practically impossible
>to fit true speed
>limiting brakes (in the sense that Vne would not be
>exceeded in a true
>vertical dive at max. a.u.w.). The first U.K. built
>gliders for which this
>applied were, I believe, some at least of the Slingsby
>Dart series.
>
>Also, if the rules were relaxed life would become a
>lot easier for the
>designer, because it would save weight and cost.
>So the rules were
>relaxed, and 'Speed limiting' came to mean 'In a dive
>at X degrees', usually
>I understand of 45 degrees.
>
>TODAY
>
>Most gliders today, including I believe all those built
>in Europe, are
>designed to JAR 22.
>
>See:
>Joint Aviation Authorities, Europe. http://www.jaa.nl/
>,
>JARs – Section 1 – JAR-22 http://www.jaa.nl/section1/jars/445499.
>>pdf .
>
>The relevant clause is:
>
>'JAR 22.73 Descent, high speed
>
>'It must be shown that the sailplane with the airbrakes
>extended, will not
>exceed VNE in a dive at an angle to the horizon of:
>
>'(a) 45° when the sailplane is approved for cloud flying
>and/or aerobatics
>when certificated in the Aerobatic or Utility Category;
>
>'(b) 30° in other cases.
>
>'[Ch. 5, 28.10.95]'
>
>Some modern gliders, including some being built today,
>probably still have
>true speed limiting brakes by the strict old definition
>given above; my
>guess is that these would all be gliders with trailing
>edge brakes or
>braking flaps such as the early Pik 20; but this would
>not necessarily be
>true for all gliders with such brakes.
>
>Some gliders were built with tailchutes, either in
>an attempt to comply with
>the old strict requirement, or because it was necessary
>if they were to
>comply with the relaxed rule. I have always understood
>that the Janus was
>fitted with a tailchute to be speed limiting in a 45
>degree dive at max.
>a.u.w. with full water ballast.
>
>At what dive angle would a Duo-Discus with full brakes
>go through Vne?
>I would be astonished if this is more than 45 degrees,
>it may very well be
>30 degrees.
>
>So if in a spin recovery, or for any other reason,
>you are diving at a very
>steep angle your air-brakes are unlikely to save you
>from exceeding Vne.
>I am sure they won't in the Nimbus 3/4 series; it was
>not a requirement for
>certification.
>
>W.J. (Bill) Dean (U.K.).
>Remove 'ic' to reply.
>
>>
>> 'Arnold Pieper' wrote in message
>> . com...
>>
>> John,
>>
>> The airbrakes were designed not only to be used for
>>approach and landing,
>> but also to avoid reaching VNE.
>>
>> Look at your glider's POH and check what is the maximum
>>speed to deploy
>> the airbrakes, and what becomes the VNE with them
>>deployed.
>>
>> In most modern design gliders, the airbrakes can be
>>deployed up to VNE,
>> and they will prevent the glider from reaching VNE
>>when fully opened.
>>
>> The airbrakes are designed for this purpose.
>>
>> Once the airbrakes are opened and will prevent you
>>from going over VNE,
>> there's no need to pull at anything even close to
>>the design limit G.
>>
>> Spin training therefore, is the best way to ease this
>>fear and learn how
>> to pull without overstressing the airframe.
>>
>> AP
>>
>> >
>> > 'John Galloway' wrote in message
>> > ...
>> >
>> > Through the contributions to the avoiding VNE thread
>> > runs the theme of the difficulty of avoiding overspeeding
>> > and/or overstressing some modern designs in accidental
>> > spin recovery. This is made more difficult than
>>>in
>> > older composite gliders because they had a little
>>>more
>> > drag and a little more (fortuitous) margin in the
>>>g
>> > limits.
>> >
>> > Is it not blindingly obvious that there is a need
>>>for
>> > an emergency drag device that does not reduce the
>>>G
>> > limits of gliders? Clearly if we all handled the
>>>recovery
>> > from inadvertent spins etc perfectly all would be
>>>well
>> > but equally clearly that does not always happen and
>> > it is a shame to lose pilots in this situation.
>> >
>> > As the Phoebus pilot pointed out a tail chute is
>>>ideal
>> > for this - providing that it can be made to actuate
>> > and jettison reliably. (I found the design used
>>>on
>> > the Kestrel particularly good and I never once had
>> > a failure for landing use.) On the other hand they
>> > are expensive and inconvenient to replace and there
>> > are several ways that they can fail.
>> >
>> > So can anyone think of a better idea than a chute?
>> > The best I can come up with is some sort of flush
>> > fitted rectangular-with the-long-edge-horizontal
>>>rear
>> > hinged airbrakes (like old fashioned automobile suicide
>> > doors) located on the fuselage sides somewhere in
>>>the
>> > region below or below/behind the wings. If they
>>>opened
>> > to about 45 degrees with a spring actuator (and limited
>> > by sliding metal stays that hinge/attach to the front
>> > of the panel and whose inner ends slid along in runners)
>> > then they would provide a lot of drag without any
>>>deep
>> > internal mechanism (such as wing airbrakes have).
>> > Once they have done their job the rear end of the
>>>brakes
>> > could be released by a spring loaded mechanism similar
>> > to the front end so that the brakes would then instantly
>> > spring to as position set out from and parallel to
>> > the fuselage so that there would be very little drag
>> > - only that provided by the stays at both ends and
>> > the brake panels edge on to the wind. That configuration
>> > would be good enough to fly home with. It would
>>>only
>> > be possible to reset these brakes on the ground and
>> > they would not replace conventional wing airbrakes
>> > for approach control - although they could have a
>>>secondary
>> > use for emergency approach control.
>> >
>> > I am envisaging something the could be included in
>> > new designs although there does not seem to be any
>> > obvious reason why such a device could not be retrofitted
>> > as a fairly major modification. The contours of
>>>the
>> > brake panels would be specific to the individual
>>>fuselage
>> > type but the mechanism could be generic. The assembly
>> > would be fairly shallow and complete within itself
>> > apart from e.g. a cable release attachment.
>> >
>> > I am not advocating a technical solution to this
>>>problem
>> > in place of spin recovery practice but I do think
>>>that
>> > there must be something that the combined intellects
>> > of the gliding community can come up with other than
>> > observing that if we get into that particular overspeeding/steep
>>>>
>> > attitude condition we are stuffed.
>> >
>> > Anyone got any simpler or better ideas? I am definitely
>> > not an engineer.
>> >
>> > John Galloway
>> >
>>
>
>
>
>

[Andy Blackburn]

I think positive static stability means that this doesn't
happen. The only certified aircraft I'm aware of that
tucks in pitch is the Learjet 20/30/50 series, but
this happens at transonic speeds as the center of lift
moves aft. The aircraft is certified with a stick puller
to ensure you never get there.

In most aircraft the phugoid mode is pretty lightly
damped and has a period on the order of tens of seconds,
so the speed can build up a bit before the nose comes
up. Are you sure that's not what you're experiencing?
The only other thing I can think of is a c.g. out
of limits, so it might be worth double checking your
weight and balance if your aircraft behaves this way.


At 06:18 01 April 2004, Eric Greenwell wrote:
>Mark Navarre wrote:
>
>>>As speed increases, the nose will come up (away from
>>>vertical) even if you
>>>don't want it to, and even with full forward trim,
>>>it would still require an
>>>honest push on the stick to maintain that attitude.
>>
>>
>> Not true with all gliders. Several modern racing
>>ships will, when trimmed
>> within CG limits for best climb performance, 'tuck'
>>or pitch down with
>> increasing airspeed, resulting in a large outside
>>loop or exceeding VNE without
>> pilot input. The crossover speed for this in my own
>>ship is about 115 kts,
>> above which slight back pressure is needed to maintain
>>speed.
>
>Which glider is that? I thought a pitch-up tendency
>with increasing
>speed was a certification requirement? And what is
>the CG position for
>this to happen? Is this 'feature' mentioned in the
>flight manaul? Sounds
>kind of scary.
>
>--
>-----
>change 'netto' to 'net' to email me directly
>
>Eric Greenwell
>Washington State
>USA
>
>

[Bill Daniels]

"Eric Greenwell" > wrote in message
...
> Mark Navarre wrote:
>
> >>As speed increases, the nose will come up (away from vertical) even if
you
> >>don't want it to, and even with full forward trim, it would still
require an
> >>honest push on the stick to maintain that attitude.
> >
> >
> > Not true with all gliders. Several modern racing ships will, when
trimmed
> > within CG limits for best climb performance, "tuck" or pitch down with
> > increasing airspeed, resulting in a large outside loop or exceeding VNE
without
> > pilot input. The crossover speed for this in my own ship is about 115
kts,
> > above which slight back pressure is needed to maintain speed.
>
> Which glider is that? I thought a pitch-up tendency with increasing
> speed was a certification requirement? And what is the CG position for
> this to happen? Is this "feature" mentioned in the flight manaul? Sounds
> kind of scary.
>
> --
> -----
> change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA
>

Though it was certainly not a "modern racing ship" my old Lark IS28 would go
neutral pitch stability at about 90 knots and become very nose heavy above
that even with negative flaps.

Bill Daniels
Nimbus 2C

[Mark Navarre]

>From: Andy Blackburn
>Date: 4/1/2004 3:35 AM Pacific Standard Time
>Message-id: >

>In most aircraft the phugoid mode is pretty lightly
>damped and has a period on the order of tens of seconds,
>so the speed can build up a bit before the nose comes
>up. Are you sure that's not what you're experiencing?

Could be this is true, I have never let the glider have it's way for long
enough to find out what the trim speed will be if I let it go. Something for a
future test flight....maybe.


-
Mark Navarre
2/5 black ace
LoCal, USA
-

[Eric Greenwell]

Bill Daniels wrote:
> "Eric Greenwell" > wrote in message
> ...
>
>>Mark Navarre wrote:
>>
>>
>>>>As speed increases, the nose will come up (away from vertical) even if
>
> you
>
>>>>don't want it to, and even with full forward trim, it would still
>
> require an
>
>>>>honest push on the stick to maintain that attitude.
>>>
>>>
>>>Not true with all gliders. Several modern racing ships will, when
>
> trimmed
>
>>>within CG limits for best climb performance, "tuck" or pitch down with
>>>increasing airspeed, resulting in a large outside loop or exceeding VNE
>
> without
>
>>>pilot input. The crossover speed for this in my own ship is about 115
>
> kts,
>
>>>above which slight back pressure is needed to maintain speed.
>>
>>Which glider is that? I thought a pitch-up tendency with increasing
>>speed was a certification requirement? And what is the CG position for
>>this to happen? Is this "feature" mentioned in the flight manaul? Sounds
>>kind of scary.

> Though it was certainly not a "modern racing ship" my old Lark IS28 would go
> neutral pitch stability at about 90 knots and become very nose heavy above
> that even with negative flaps.

Was that a common experience, or just your particular IS28? I'm
wondering if there might be a rigging error. None of the gliders I've
owned has exhibited that; in fact, all of them ran out (or required
nearly full) of forward trim nearing Vne. THese gliders are the Ka-6E,
Std Cirrus, Libelle H301, ASW 20 C, ASH 26 E, Blanik. The Cirrus had a
particularly noticeable concave under section on the elevator to induce
this behavior.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Andreas Maurer]

On Thu, 01 Apr 2004 07:58:46 -0800, Eric Greenwell
> wrote:

>> Though it was certainly not a "modern racing ship" my old Lark IS28 would go
>> neutral pitch stability at about 90 knots and become very nose heavy above
>> that even with negative flaps.

This behaviour of a neutrally instable aircraft is typical for a CG
that is out of range.

>Was that a common experience, or just your particular IS28? I'm
>wondering if there might be a rigging error. None of the gliders I've
>owned has exhibited that; in fact, all of them ran out (or required
>nearly full) of forward trim nearing Vne.


Just like you I also have never flown an aircraft that did not hve
positive pitch stability.

Bye
Andreas

[Arnold Pieper]

I don't know where you guys get these things from, but this behaviour means
these gliders should have their certifications cancelled.

I've never flown anything with these characteristics.

"Mark Navarre" > wrote in message
...
> >From: "Arnold Pieper"
> >Date: 3/31/2004 1:16 PM Pacific Standard Time
> >Message-id: >
>
> >Maybe true if "near vertical", however, staying at a near vertical dive
is
> >something that requires a conscient effort.
> >The glider won't just stay there on its own.
> >To remain in a 90 degree vertical dive requires a significant amount of
> >forward stick force and concentration.
> >As speed increases, the nose will come up (away from vertical) even if
you
> >don't want it to, and even with full forward trim, it would still require
an
> >honest push on the stick to maintain that attitude.
>
> Not true with all gliders. Several modern racing ships will, when trimmed
> within CG limits for best climb performance, "tuck" or pitch down with
> increasing airspeed, resulting in a large outside loop or exceeding VNE
without
> pilot input. The crossover speed for this in my own ship is about 115
kts,
> above which slight back pressure is needed to maintain speed.
>
> -
> Mark Navarre
> 2/5 black ace
> LoCal, USA
> -

[Arnold Pieper]

You're affraid of something that

"Todd Pattist" > wrote in message
...
> "Arnold Pieper" > wrote:
>
> >Don't be affraid to open the airbrakes at high speed, believe me, the
> >manufacturer is just a little smarter than that.
>
> I'm not afraid to open them at high speed, I'm afraid to
> lower the G-limit when I need G-s to recover. I've seen too
> many accident reports where structural failure was
> attributed to overstressing with the brakes open.
>
> >You have to be careful at high speed just because they tend to jump out
more
> >easily, so, have a firm hand on it.
> >
> >Real aerobatic training (as opposed to some occasional loops) will
clarify a
> >lot of this.
>
> Although it's been long time, my training was by a national
> glider aerobatic champion.
>
>
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

[Arnold Pieper]

These reports led you to the wrong conclusion.
Overstress is the key here, weahter with or without airbrakes.

It's a lot easier to overstress the structure or eventually even cause
flutter by trying to recover from a high speed dive without using the
brakes.

"Todd Pattist" > wrote in message
...
> "Arnold Pieper" > wrote:
>
> >Don't be affraid to open the airbrakes at high speed, believe me, the
> >manufacturer is just a little smarter than that.
>
> I'm not afraid to open them at high speed, I'm afraid to
> lower the G-limit when I need G-s to recover. I've seen too
> many accident reports where structural failure was
> attributed to overstressing with the brakes open.
>
> >You have to be careful at high speed just because they tend to jump out
more
> >easily, so, have a firm hand on it.
> >
> >Real aerobatic training (as opposed to some occasional loops) will
clarify a
> >lot of this.
>
> Although it's been long time, my training was by a national
> glider aerobatic champion.
>
>
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

[Jon Meyer]

I thought you flew an ASW20 (might be mistaken)? This
is one ship where the wing twist at high speed results
in a subtle trim change that you might not even notice.
At high speed the stick eventually needs to be brought
slightly back to avoid continuing acceleration. The
faster you go the further back it needs to come. Don't
get me wrong, it is VERY subtle and you probably wouldnt
ever notice it. But there was some speculation that
the ASW20 accident mentioned earlier was the result
of a speed being reached (above VNE) where the trim
change was such that the stick was on the back stop
and the sailplane was still pitching nose down.

The reason that this behaviour is allowed is because
it isn't dangerous (or even noticable) unless you exceed
VNE.

This is just stuff I have heard around, so not sure
if it is 100% true. But I have heard it from some pretty
reliable people.


At 23:42 01 April 2004, Arnold Pieper wrote:
>I don't know where you guys get these things from,
>but this behaviour means
>these gliders should have their certifications cancelled.
>
>I've never flown anything with these characteristics.
>
>'Mark Navarre' wrote in message
...
>> >From: 'Arnold Pieper'
>> >Date: 3/31/2004 1:16 PM Pacific Standard Time
>> >Message-id:
>>
>> >Maybe true if 'near vertical', however, staying at
>>>a near vertical dive
>is
>> >something that requires a conscient effort.
>> >The glider won't just stay there on its own.
>> >To remain in a 90 degree vertical dive requires a
>>>significant amount of
>> >forward stick force and concentration.
>> >As speed increases, the nose will come up (away from
>>>vertical) even if
>you
>> >don't want it to, and even with full forward trim,
>>>it would still require
>an
>> >honest push on the stick to maintain that attitude.
>>
>> Not true with all gliders. Several modern racing
>>ships will, when trimmed
>> within CG limits for best climb performance, 'tuck'
>>or pitch down with
>> increasing airspeed, resulting in a large outside
>>loop or exceeding VNE
>without
>> pilot input. The crossover speed for this in my own
>>ship is about 115
>kts,
>> above which slight back pressure is needed to maintain
>>speed.
>>
>> -
>> Mark Navarre
>> 2/5 black ace
>> LoCal, USA
>> -
>
>
>

[Bert Willing]

I own and fly an ASW 20, and the behaviour you describe is definitively
complete nonsense.
Even approaching Vne you need to positively push the stick to maintain
speed.

--
Bert Willing

ASW20 "TW"


"Jon Meyer" > a écrit dans le message
de ...
> I thought you flew an ASW20 (might be mistaken)? This
> is one ship where the wing twist at high speed results
> in a subtle trim change that you might not even notice.
> At high speed the stick eventually needs to be brought
> slightly back to avoid continuing acceleration. The
> faster you go the further back it needs to come. Don't
> get me wrong, it is VERY subtle and you probably wouldnt
> ever notice it. But there was some speculation that
> the ASW20 accident mentioned earlier was the result
> of a speed being reached (above VNE) where the trim
> change was such that the stick was on the back stop
> and the sailplane was still pitching nose down.
>
> The reason that this behaviour is allowed is because
> it isn't dangerous (or even noticable) unless you exceed
> VNE.
>
> This is just stuff I have heard around, so not sure
> if it is 100% true. But I have heard it from some pretty
> reliable people.
>
>
> At 23:42 01 April 2004, Arnold Pieper wrote:
> >I don't know where you guys get these things from,
> >but this behaviour means
> >these gliders should have their certifications cancelled.
> >
> >I've never flown anything with these characteristics.
> >
> >'Mark Navarre' wrote in message
> ...
> >> >From: 'Arnold Pieper'
> >> >Date: 3/31/2004 1:16 PM Pacific Standard Time
> >> >Message-id:
> >>
> >> >Maybe true if 'near vertical', however, staying at
> >>>a near vertical dive
> >is
> >> >something that requires a conscient effort.
> >> >The glider won't just stay there on its own.
> >> >To remain in a 90 degree vertical dive requires a
> >>>significant amount of
> >> >forward stick force and concentration.
> >> >As speed increases, the nose will come up (away from
> >>>vertical) even if
> >you
> >> >don't want it to, and even with full forward trim,
> >>>it would still require
> >an
> >> >honest push on the stick to maintain that attitude.
> >>
> >> Not true with all gliders. Several modern racing
> >>ships will, when trimmed
> >> within CG limits for best climb performance, 'tuck'
> >>or pitch down with
> >> increasing airspeed, resulting in a large outside
> >>loop or exceeding VNE
> >without
> >> pilot input. The crossover speed for this in my own
> >>ship is about 115
> >kts,
> >> above which slight back pressure is needed to maintain
> >>speed.
> >>
> >> -
> >> Mark Navarre
> >> 2/5 black ace
> >> LoCal, USA
> >> -
> >
> >
> >
>
>
>

[Andreas Maurer]

On 2 Apr 2004 09:26:34 GMT, Jon Meyer
> wrote:


>This is just stuff I have heard around, so not sure
>if it is 100% true. But I have heard it from some pretty
>reliable people.

Basic rule #1 about aviation rumours:
Never believe anything as long as you have not seen it yourself.

The behaviour described above is, as Bert alreay pointed out, absolute
nonsense and exactly the contrary of how a 20 behavies in reality.


Bye
Andreas

[JJ Sinclair]

>
>The behaviour described above is, as Bert alreay pointed out, absolute
>nonsense and exactly the contrary of how a 20 behavies in reality.
>

It's not all BS, there was this Doctor that extended the wing span on his ship,
back in the '70's. He brought a new meaning to the term, *final glide* as the
wing tips dug-in and he almost completed an outside loop, with the stick full
back, but the ground got in the way. Wing twist at high speed is real.
JJ Sinclair

[Mark Navarre]

>Subject: Re: Devices for avoiding VNE?
>From: Andreas Maurer
>Date: 4/2/2004 5:48 AM Pacific Standard Time
>Message-id: >
>Basic rule #1 about aviation rumours:
>Never believe anything as long as you have not seen it yourself.
>
>The behaviour described above is, as Bert alreay pointed out, absolute
>nonsense and exactly the contrary of how a 20 behavies in reality.

I have seen it myself, my ship was not out of CG limits, the effect is subtle,
but present nevertheless. Other pliots with AS-W20's may not experience the
tuck due to flying with a further forward CG and resulting trim speed change,
thereby canceling the aeroelastic twist of the wings. 20 B's have stiffer
wings than the A or C, by the way, and may not twist as much.
The speed at which this begins to occur on my ship is out of the normal range
of efficient cruising speed anyway. Just fly the plane...put the stick where
it gives you the speed you want and keep it there until you want a different
speed. It's not autopilot!


-
Mark Navarre
2/5 black ace
LoCal, USA
-

[Eric Greenwell]

JJ Sinclair wrote:
>>The behaviour described above is, as Bert alreay pointed out, absolute
>>nonsense and exactly the contrary of how a 20 behavies in reality.

>
> It's not all BS, there was this Doctor that extended the wing span on his ship,
> back in the '70's. He brought a new meaning to the term, *final glide* as the
> wing tips dug-in and he almost completed an outside loop, with the stick full
> back, but the ground got in the way. Wing twist at high speed is real.
> JJ Sinclair

I think the context here is "certified gliders" operated within their
limits, are supposed to have positive stability at Vne. If you have one
that doesn't, this suggests there is something wrong with your glider.

I'm sure we all agree that wing twist can happen, and we are not
surprised it might happen to someone that extended the span on his
glider, or exceeds Vne by 40 or 50 knots.
--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Andy Blackburn]

I a bit suspicious of this whole wing twist thing.
Since the center of lift for most airfoils is at about
0.25 chord, which is generally a bit haead of the spar,
you'd expect the natural aerodynamic forces to generate
neutral to positive twisting with loading. The only
counter-examples I know of are in jet fighters. The
F-100 was known to have aileron reversal at maximum
dynamic pressure (transonic at low altitude) under
high Gs.

On a glider you would have to have a lot of washout
built into the tips to get it to twist because you
would need to generate negative angle of attack at
the tip. I guess this is possible if you modify your
glider extensively, or maybe if do an aggressive negative-G
pushover at a high enough speed. Neither of those
are in my bag of tricks so I'll consider myself relatively
safe for now.

At 16:54 02 April 2004, Eric Greenwell wrote:
>JJ Sinclair wrote:
>>>The behaviour described above is, as Bert alreay pointed
>>>out, absolute
>>>nonsense and exactly the contrary of how a 20 behavies
>>>in reality.
>
>>
>> It's not all BS, there was this Doctor that extended
>>the wing span on his ship,
>> back in the '70's. He brought a new meaning to the
>>term, *final glide* as the
>> wing tips dug-in and he almost completed an outside
>>loop, with the stick full
>> back, but the ground got in the way. Wing twist at
>>high speed is real.
>> JJ Sinclair
>
>I think the context here is 'certified gliders' operated
>within their
>limits, are supposed to have positive stability at
>Vne. If you have one
>that doesn't, this suggests there is something wrong
>with your glider.
>
>I'm sure we all agree that wing twist can happen, and
>we are not
>surprised it might happen to someone that extended
>the span on his
>glider, or exceeds Vne by 40 or 50 knots.
>--
>-----
>change 'netto' to 'net' to email me directly
>
>Eric Greenwell
>Washington State
>USA
>
>

[JJ Sinclair]

>
>I a bit suspicious of this whole wing twist thing.

Take a K-6 up to 100 and look at the tips.

Take an ASH-25 up to 80 with landing flaps on and look at the tips.

In the case of the K-6, she does have a few degrees of tip wash-out (leading
edge down)

In the case of the ASH-25 with landing flaps on, Only the inboard flaps go
down, the outboard flaps and ailerons go up to produce a negative angle of
attack.

So why do the wings in both cases bend down?

Why does the B-52 use spoilers instead of ailerons? Because at higher airspeeds
an aileron input causes the wing to bend and can cause the ship to turn in the
opposite direction (wing twist)

Even in a *certified* ship, if the wings start to tuck under and you don't
catch it right away, you could find yourself in a situation where elevator
won't stop the pitch down action. Now, all of this is at or above VNE, so if we
are flying our glass slippers within limits, we should be OK.
JJ Sinclair

[Eric Greenwell]

Andy Blackburn wrote:
> I a bit suspicious of this whole wing twist thing.
> Since the center of lift for most airfoils is at about
> 0.25 chord, which is generally a bit haead of the spar,
> you'd expect the natural aerodynamic forces to generate
> neutral to positive twisting with loading.

I think you are right to be suspicious about the importance of wing
twist in a certified glider, but not for your reason. Most gliders do
have wing twist built into them, and the pitching momemt of the airfoil
also is twisting the wing in the same direction. The reason we don't
have worry about it is the designer knows about these factors, used
sufficent structure to avoid excessive twisting, then validated his
design with structural and flight tests.

A glider operated well outside it's limits, a damaged one, or a modified
one... Plenty to worry about then.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Arnold Pieper]

Good if that's what makes YOU feel safe !


"Todd Pattist" > wrote in message
...
> "Arnold Pieper" > wrote:
>
> >These reports led you to the wrong conclusion.
> >Overstress is the key here, weahter with or without airbrakes.
>
> My load limit is 5 G's brakes closed, 3.5 G's brakes open.
> If you want to pull the nose up at 5 G's to avoid hitting
> the ground, you can do it brakes closed, but not brakes
> open. If your adrenaline kicks in as you pull back, you can
> pull until you feel 5 G's if you leave the brakes closed,
> but only to 3.5G's if you open them.
> Todd Pattist - "WH" Ventus C
> (Remove DONTSPAMME from address to email reply.)

[Andy Blackburn]

Okay - point taken on designs with lots of tip washout
or inbord flaps deployed. But the wing twist discussion
was really a secondary point in the dialog about pitch
stability overall, and I'm not sure that a twisting
at the tip would contribute very much to making the
glider unstable overall.

I still think it's not reasonable to expect that a
glider would be certified where you'd get enough structural
twisting to upset the overall stability of the aircraft.
More broadly, I doubt that you'll find a certified
aircraft that has a pitching moment that becomes more
nose down with increasing speed no matter what the
reason. The feds are unlikely to smile on a design
with static instability at any speed.

I remain convinced that if your sailplane exhibits
pitch instability you have a c.g. problem, a rigging
problem, your aircraft has been modified or you are
outside the certified operating limits.


At 18:42 02 April 2004, Jj Sinclair wrote:
>>
>>I a bit suspicious of this whole wing twist thing.
>
>Take a K-6 up to 100 and look at the tips.
>
>Take an ASH-25 up to 80 with landing flaps on and
>look at the tips.
>
>In the case of the K-6, she does have a few degrees
>of tip wash-out (leading
>edge down)
>
>In the case of the ASH-25 with landing flaps on, Only
>the inboard flaps go
>down, the outboard flaps and ailerons go up to produce
>a negative angle of
>attack.
>
>So why do the wings in both cases bend down?
>
>Why does the B-52 use spoilers instead of ailerons?
>Because at higher airspeeds
>an aileron input causes the wing to bend and can cause
>the ship to turn in the
>opposite direction (wing twist)
>
>Even in a *certified* ship, if the wings start to tuck
>under and you don't
>catch it right away, you could find yourself in a situation
>where elevator
>won't stop the pitch down action. Now, all of this
>is at or above VNE, so if we
>are flying our glass slippers within limits, we should
>be OK.
>JJ Sinclair
>

[ADP]

Well,

Although not directly related to gliders (except really fast ones), look up
"mach tuck" and you will find several certified aircraft that tend to nose
down as speed increases.

Critical mach is a aeronautics term that refers to the speed at which some
of the airflow on a wing becomes supersonic. When this occurs the
distribution of forces on the wing changes suddenly and dramatically,
typically leading to a strong nose-down force on the aircraft. This effect
led to a number of accidents in the 1930s and 1940s, when aircraft in a dive
would hit critical mach and continue to push over into a steeper and steeper
dive. This problem is often lumped in with the catch-all phrase
compressibility.

Wings generate much of their lift due to the Bernoulli effect; by speeding
up the airflow over the top of the wing, the air has less density on top
than on the bottom, leading to a net upward force. The relative difference
in speed is due largely to the wing's shape, so the difference in speed
remains a fairly constant ratio over a wide range of speeds.

But if the air speed on the top of the wing is faster than on the bottom,
there will be some speed where the air on top reaches the speed of sound.
This is the critical mach. When this happens shock waves form on the upper
wing at the point where the flow becomes supersonic, typically behind the
midline of the chord. Shock waves generate lift of their own, so the lift of
the wing suddenly moves rearward, twisting it down. This effect is known as
mach tuck.

;0)

Allan

"Andy Blackburn" > wrote in message
...
> Okay - point taken on designs with lots of tip washout
> or inbord flaps deployed. But the wing twist discussion
> was really a secondary point in the dialog about pitch
> stability overall, and I'm not sure that a twisting
> at the tip would contribute very much to making the
> glider unstable overall.
>
> I still think it's not reasonable to expect that a
> glider would be certified where you'd get enough structural
> twisting to upset the overall stability of the aircraft.
> More broadly, I doubt that you'll find a certified
> aircraft that has a pitching moment that becomes more
> nose down with increasing speed no matter what the
> reason. The feds are unlikely to smile on a design
> with static instability at any speed.
>
>

[Andreas Maurer]

On 02 Apr 2004 14:51:49 GMT, (JJ Sinclair) wrote:


>It's not all BS, there was this Doctor that extended the wing span on his ship,
>back in the '70's. He brought a new meaning to the term, *final glide* as the
>wing tips dug-in and he almost completed an outside loop, with the stick full
>back, but the ground got in the way. Wing twist at high speed is real.

Basic rule #2 in aviation:
Better know what you are doing if you want to become an old pilot.

Any airfoil with a negative Cm0 (this means any glider with a tail)
will twist at high speed and low CL's... but the wing needs to be
strong enough to prevent excessive twist.
If it is not (because of a design flaw or a modification - see above)
your day is going to be ruined.

And if the wing is able to twist enough to make the ship unstable, I
am absolutely sure that it will not get a certificate. Certainly not
by German authorities.





Bye
Andreas

[Andreas Maurer]

On 02 Apr 2004 16:17:09 GMT, (Mark Navarre)
wrote:


>I have seen it myself, my ship was not out of CG limits, the effect is subtle,
>but present nevertheless. Other pliots with AS-W20's may not experience the
>tuck due to flying with a further forward CG and resulting trim speed change,
>thereby canceling the aeroelastic twist of the wings. 20 B's have stiffer
>wings than the A or C, by the way, and may not twist as much.
>The speed at which this begins to occur on my ship is out of the normal range
>of efficient cruising speed anyway. Just fly the plane...put the stick where
>it gives you the speed you want and keep it there until you want a different
>speed. It's not autopilot!

Interesting. The 20's I was flying could all be trimmed to about 230
kp/h with the CG at about 90 percent (different CG's, only my club's
20L was optimized for my weight and allowed a truly tail-heavy CG),
independent of the configuration (15 or 16.60 meters). I never felt
the need to go back further with the CG - are you flying yours with a
CG at the end if the allowed range? I guess you carried no water,
correct?


Bye
Andreas

[Arnold Pieper]

A+ for research initiative, D- for applicability.

Mach tuck affects certain high speed aircraft (high mach numbers, jets only)
with swept back wings, when they exceed their Mmo.
When flying within their normal certified speed ranges, they do not present
this abnormality.

As someone already posted, no aircraft would be certified with instability
being a part of its normal flight envelope.

"ADP" > wrote in message
...
> Well,
>
> Although not directly related to gliders (except really fast ones), look
up
> "mach tuck" and you will find several certified aircraft that tend to nose
> down as speed increases.
>
> Critical mach is a aeronautics term that refers to the speed at which some
> of the airflow on a wing becomes supersonic. When this occurs the
> distribution of forces on the wing changes suddenly and dramatically,
> typically leading to a strong nose-down force on the aircraft. This effect
> led to a number of accidents in the 1930s and 1940s, when aircraft in a
dive
> would hit critical mach and continue to push over into a steeper and
steeper
> dive. This problem is often lumped in with the catch-all phrase
> compressibility.
>
> Wings generate much of their lift due to the Bernoulli effect; by speeding
> up the airflow over the top of the wing, the air has less density on top
> than on the bottom, leading to a net upward force. The relative difference
> in speed is due largely to the wing's shape, so the difference in speed
> remains a fairly constant ratio over a wide range of speeds.
>
> But if the air speed on the top of the wing is faster than on the bottom,
> there will be some speed where the air on top reaches the speed of sound.
> This is the critical mach. When this happens shock waves form on the upper
> wing at the point where the flow becomes supersonic, typically behind the
> midline of the chord. Shock waves generate lift of their own, so the lift
of
> the wing suddenly moves rearward, twisting it down. This effect is known
as
> mach tuck.
>
> ;0)
>
> Allan
>
> "Andy Blackburn" > wrote in message
> ...
> > Okay - point taken on designs with lots of tip washout
> > or inbord flaps deployed. But the wing twist discussion
> > was really a secondary point in the dialog about pitch
> > stability overall, and I'm not sure that a twisting
> > at the tip would contribute very much to making the
> > glider unstable overall.
> >
> > I still think it's not reasonable to expect that a
> > glider would be certified where you'd get enough structural
> > twisting to upset the overall stability of the aircraft.
> > More broadly, I doubt that you'll find a certified
> > aircraft that has a pitching moment that becomes more
> > nose down with increasing speed no matter what the
> > reason. The feds are unlikely to smile on a design
> > with static instability at any speed.
> >
> >
>
>

[d b]

Do you include rudder lock as an instability? How about dynamic stability?
What about downsprings, bob weights and other stability enhancement devices?
Stability is a really broad subject.


In article >, "Arnold Pieper"
> wrote:
>A+ for research initiative, D- for applicability.
>
>Mach tuck affects certain high speed aircraft (high mach numbers, jets only)
>with swept back wings, when they exceed their Mmo.
>When flying within their normal certified speed ranges, they do not present
>this abnormality.
>
>As someone already posted, no aircraft would be certified with instability
>being a part of its normal flight envelope.
>
>"ADP" > wrote in message
...
>> Well,
>>
>> Although not directly related to gliders (except really fast ones), look
>up
>> "mach tuck" and you will find several certified aircraft that tend to nose
>> down as speed increases.
>>
>> Critical mach is a aeronautics term that refers to the speed at which some
>> of the airflow on a wing becomes supersonic. When this occurs the
>> distribution of forces on the wing changes suddenly and dramatically,
>> typically leading to a strong nose-down force on the aircraft. This effect
>> led to a number of accidents in the 1930s and 1940s, when aircraft in a
>dive
>> would hit critical mach and continue to push over into a steeper and
>steeper
>> dive. This problem is often lumped in with the catch-all phrase
>> compressibility.
>>
>> Wings generate much of their lift due to the Bernoulli effect; by speeding
>> up the airflow over the top of the wing, the air has less density on top
>> than on the bottom, leading to a net upward force. The relative difference
>> in speed is due largely to the wing's shape, so the difference in speed
>> remains a fairly constant ratio over a wide range of speeds.
>>
>> But if the air speed on the top of the wing is faster than on the bottom,
>> there will be some speed where the air on top reaches the speed of sound.
>> This is the critical mach. When this happens shock waves form on the upper
>> wing at the point where the flow becomes supersonic, typically behind the
>> midline of the chord. Shock waves generate lift of their own, so the lift
>of
>> the wing suddenly moves rearward, twisting it down. This effect is known
>as
>> mach tuck.
>>
>> ;0)
>>
>> Allan
>>
>> "Andy Blackburn" > wrote in message
>> ...
>> > Okay - point taken on designs with lots of tip washout
>> > or inbord flaps deployed. But the wing twist discussion
>> > was really a secondary point in the dialog about pitch
>> > stability overall, and I'm not sure that a twisting
>> > at the tip would contribute very much to making the
>> > glider unstable overall.
>> >
>> > I still think it's not reasonable to expect that a
>> > glider would be certified where you'd get enough structural
>> > twisting to upset the overall stability of the aircraft.
>> > More broadly, I doubt that you'll find a certified
>> > aircraft that has a pitching moment that becomes more
>> > nose down with increasing speed no matter what the
>> > reason. The feds are unlikely to smile on a design
>> > with static instability at any speed.
>> >
>> >
>>
>>
>
>

[Jan-Olov Newborg]

"ADP" > wrote in message >...
> Well,
>
> Although not directly related to gliders (except really fast ones), look up
> "mach tuck" and you will find several certified aircraft that tend to nose
> down as speed increases.
>
> Critical mach is a aeronautics term that refers to the speed at which some
> of the airflow on a wing becomes supersonic. When this occurs the
> distribution of forces on the wing changes suddenly and dramatically,
> typically leading to a strong nose-down force on the aircraft. This effect
> led to a number of accidents in the 1930s and 1940s, when aircraft in a dive
> would hit critical mach and continue to push over into a steeper and steeper
> dive. This problem is often lumped in with the catch-all phrase
> compressibility.
>
> Wings generate much of their lift due to the Bernoulli effect; by speeding
> up the airflow over the top of the wing, the air has less density on top
> than on the bottom, leading to a net upward force. The relative difference
> in speed is due largely to the wing's shape, so the difference in speed
> remains a fairly constant ratio over a wide range of speeds.
>
> But if the air speed on the top of the wing is faster than on the bottom,
> there will be some speed where the air on top reaches the speed of sound.
> This is the critical mach. When this happens shock waves form on the upper
> wing at the point where the flow becomes supersonic, typically behind the
> midline of the chord. Shock waves generate lift of their own, so the lift of
> the wing suddenly moves rearward, twisting it down. This effect is known as
> mach tuck.
>

How do you fly inverted using "Bernoulli Effect"?


Jan-Olov Newborg

[ADP]

A for effort, D for accuracy. The DC-8 Could not be flown at altitude with
out it's PTC (Pitch Trim Compensator) being operative.
The function of the PTC was to protect against mach tuck.

Since the DC-8 was undoubtedly certified, the argument is invalid.

Had you read my post you would have noticed the reference to supersonic
airflow which presumably does not apply to gliders.
On the other hand, a P-38 with a critical mach number of .69 is hardly a jet
and has straight wings.
Several were lost in early testing because the phenomenon of mach tuck was
not well known.

In fact, sweepback is a design factor that helps delay critical mach to
higher numbers.

Not to make too fine a point but any aircraft, if flown fast enough without
breaking up, can be subject to mach tuck.

Allan

"Arnold Pieper" > wrote in message
m...
> A+ for research initiative, D- for applicability.
>
> Mach tuck affects certain high speed aircraft (high mach numbers, jets
> only)
> with swept back wings, when they exceed their Mmo.
> When flying within their normal certified speed ranges, they do not
> present
> this abnormality.
>
> As someone already posted, no aircraft would be certified with instability
> being a part of its normal flight envelope.
>
> "ADP" > wrote in message
> ...
>> Well,
>>
>> Although not directly related to gliders (except really fast ones), look
> up
>> "mach tuck" and you will find several certified aircraft that tend to
>> nose
>> down as speed increases.
>>
>> Critical mach is a aeronautics term that refers to the speed at which
>> some
>> of the airflow on a wing becomes supersonic. When this occurs the
>> distribution of forces on the wing changes suddenly and dramatically,
>> typically leading to a strong nose-down force on the aircraft. This
>> effect
>> led to a number of accidents in the 1930s and 1940s, when aircraft in a
> dive
>> would hit critical mach and continue to push over into a steeper and
> steeper
>> dive. This problem is often lumped in with the catch-all phrase
>> compressibility.
>>
>> Wings generate much of their lift due to the Bernoulli effect; by
>> speeding
>> up the airflow over the top of the wing, the air has less density on top
>> than on the bottom, leading to a net upward force. The relative
>> difference
>> in speed is due largely to the wing's shape, so the difference in speed
>> remains a fairly constant ratio over a wide range of speeds.
>>
>> But if the air speed on the top of the wing is faster than on the bottom,
>> there will be some speed where the air on top reaches the speed of sound.
>> This is the critical mach. When this happens shock waves form on the
>> upper
>> wing at the point where the flow becomes supersonic, typically behind the
>> midline of the chord. Shock waves generate lift of their own, so the lift
> of
>> the wing suddenly moves rearward, twisting it down. This effect is known
> as
>> mach tuck.
>>
>> ;0)
>>
>> Allan
>>

[ADP]

It's called angle of attack.

Allan

"Jan-Olov Newborg" > wrote in message
om...
> "ADP" > wrote in message
> >...
>> Well,
>>
>>>>
>
> How do you fly inverted using "Bernoulli Effect"?
>
>
> Jan-Olov Newborg

[Arnold Pieper]

Allan,

I think we're generalizing too much here.

The "distribution of forces on the wings change" as you posted, that is the
key when you reach high speeds in sub-sonic aircraft.
Supersonic aircraft have supercritical wing profiles and are a different
story altogether.

On sub-sonic, sweptback wings, the shock waves form first at the wing root
and destroy the lift there (boundary layer separates aft of it), close to
the fuselage.
Since the wing roots are "forward" of the rest of the wing in a swept back
design, the rest of the wing that continues to work being further aft,
generates the pitch down tendency.

The stories about early high-speed flights ending up flying into the ground
are related to the elevator not being the one-piece stabilators that we see
in all supersonic aircraft today.
The "regular" horizontal stabilizer-and-elevator that we see in most
sub-sonic aircraft suffers from control reversal close to Mach 1, and that's
why the one-piece stabilator was developed, it does not suffer from
control-reversal.

Mach Trim is required on SuperSonic aircraft (with supercritical airfoils),
in which the Center of Lift moves back significantly as the aircraft
accelerates through Mach 1. This phenomenon doesn't affect sub-sonic
aircraft in a very significant way because when the shock wave forms on the
wing roots, it destroys the lift there, as opposed to moving the AC back.

Either way, on our gliders, none of these things really matter.

"ADP" > wrote in message
...
> A for effort, D for accuracy. The DC-8 Could not be flown at altitude
with
> out it's PTC (Pitch Trim Compensator) being operative.
> The function of the PTC was to protect against mach tuck.
>
> Since the DC-8 was undoubtedly certified, the argument is invalid.
>
> Had you read my post you would have noticed the reference to supersonic
> airflow which presumably does not apply to gliders.
> On the other hand, a P-38 with a critical mach number of .69 is hardly a
jet
> and has straight wings.
> Several were lost in early testing because the phenomenon of mach tuck was
> not well known.
>
> In fact, sweepback is a design factor that helps delay critical mach to
> higher numbers.
>
> Not to make too fine a point but any aircraft, if flown fast enough
without
> breaking up, can be subject to mach tuck.
>
> Allan
>
> "Arnold Pieper" > wrote in message
> m...
> > A+ for research initiative, D- for applicability.
> >
> > Mach tuck affects certain high speed aircraft (high mach numbers, jets
> > only)
> > with swept back wings, when they exceed their Mmo.
> > When flying within their normal certified speed ranges, they do not
> > present
> > this abnormality.
> >
> > As someone already posted, no aircraft would be certified with
instability
> > being a part of its normal flight envelope.
> >
> > "ADP" > wrote in message
> > ...
> >> Well,
> >>
> >> Although not directly related to gliders (except really fast ones),
look
> > up
> >> "mach tuck" and you will find several certified aircraft that tend to
> >> nose
> >> down as speed increases.
> >>
> >> Critical mach is a aeronautics term that refers to the speed at which
> >> some
> >> of the airflow on a wing becomes supersonic. When this occurs the
> >> distribution of forces on the wing changes suddenly and dramatically,
> >> typically leading to a strong nose-down force on the aircraft. This
> >> effect
> >> led to a number of accidents in the 1930s and 1940s, when aircraft in a
> > dive
> >> would hit critical mach and continue to push over into a steeper and
> > steeper
> >> dive. This problem is often lumped in with the catch-all phrase
> >> compressibility.
> >>
> >> Wings generate much of their lift due to the Bernoulli effect; by
> >> speeding
> >> up the airflow over the top of the wing, the air has less density on
top
> >> than on the bottom, leading to a net upward force. The relative
> >> difference
> >> in speed is due largely to the wing's shape, so the difference in speed
> >> remains a fairly constant ratio over a wide range of speeds.
> >>
> >> But if the air speed on the top of the wing is faster than on the
bottom,
> >> there will be some speed where the air on top reaches the speed of
sound.
> >> This is the critical mach. When this happens shock waves form on the
> >> upper
> >> wing at the point where the flow becomes supersonic, typically behind
the
> >> midline of the chord. Shock waves generate lift of their own, so the
lift
> > of
> >> the wing suddenly moves rearward, twisting it down. This effect is
known
> > as
> >> mach tuck.
> >>
> >> ;0)
> >>
> >> Allan
> >>
>
>

[Arnold Pieper]

I'm not sure how you want to relate your questions with what's being
discussed.
But aircraft need to have a predictable behaviour and a predictable response
to control inputs.
To be certified, a design sometimes needs to use devices so that it has a
predictable behaviour and response to control inputs.
Springs (on older aircraft and most gliders) and Bob weights are commonly
used to make pitch control heavier with higher G-loads, thus helping prevent
us from overstressing the airframe.
Springs are also used on gliders in place of aerodynamic Trim controls (such
as trim tabs or variable incidence horizontal stabilizers ), so that stick
forces remain light throughout the flight and CG envelopes.

Weights are also used in some designs to balance control surfaces (called
"mass balanced"), since a fully balanced control surface is less prone to
flutter.

All of these things, as well as Delta Fins on some jets, computer software
in fly-by-wire systems, stick pushers, stick shakers, yaw dampers, and yet
some other things, are all used to guarantee that the behaviours are
predictable and within certain standards on all flying things.
Basically to guarantee that we push to nose-over, pull to bring the nose up,
move the stick right to bank right, left to bank left, and so on.

I tried to answer your question in the most relevant way.

"d b" > wrote in message
link.net...
> Do you include rudder lock as an instability? How about dynamic
stability?
> What about downsprings, bob weights and other stability enhancement
devices?
> Stability is a really broad subject.
>

[Paul Repacholi]

"Arnold Pieper" > writes:

::bzzzzzt::thank you for playing::

> Mach tuck affects certain high speed aircraft (high mach numbers,
> jets only) with swept back wings, when they exceed their Mmo. When
> flying within their normal certified speed ranges, they do not
> present this abnormality.

> As someone already posted, no aircraft would be certified with
> instability being a part of its normal flight envelope.

Concorde, when it was acelaring through transonic speeds had to do a
large fuel xfer to the aft tanks to conpensate for the strong nose
down trim shift.

It was rumoured to be certified :)

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

[d b]

You got it. Stability isn't really defined as the aerodynamics of the plane.
It is defined as what the pilot sees. You didn't mention that
dynamic instability is quite common and is usually not a serious issue.
Rudder lock is another story. This should not happen in the speed
range of the aircraft. In the one that I flew, it happened at very low
speeds, in a highly yawed condition, on purpose, and was easy to
overcome. I was looking at this on purpose because it was evident that
the rudder forces were getting lighter with increased deflection in one
direction and different in the other direction. I thought it deserved a closer
look before any unexpected surprises might happen. Something to keep
in mind for the pilots who like spins. I don't.


In article >, "Arnold Pieper"
> wrote:
>I'm not sure how you want to relate your questions with what's being
>discussed.
>But aircraft need to have a predictable behaviour and a predictable response
>to control inputs.
>To be certified, a design sometimes needs to use devices so that it has a
>predictable behaviour and response to control inputs.
>Springs (on older aircraft and most gliders) and Bob weights are commonly
>used to make pitch control heavier with higher G-loads, thus helping prevent
>us from overstressing the airframe.
>Springs are also used on gliders in place of aerodynamic Trim controls (such
>as trim tabs or variable incidence horizontal stabilizers ), so that stick
>forces remain light throughout the flight and CG envelopes.
>
>Weights are also used in some designs to balance control surfaces (called
>"mass balanced"), since a fully balanced control surface is less prone to
>flutter.
>
>All of these things, as well as Delta Fins on some jets, computer software
>in fly-by-wire systems, stick pushers, stick shakers, yaw dampers, and yet
>some other things, are all used to guarantee that the behaviours are
>predictable and within certain standards on all flying things.
>Basically to guarantee that we push to nose-over, pull to bring the nose up,
>move the stick right to bank right, left to bank left, and so on.
>
>I tried to answer your question in the most relevant way.
>
>"d b" > wrote in message
link.net...
>> Do you include rudder lock as an instability? How about dynamic
>stability?
>> What about downsprings, bob weights and other stability enhancement
>devices?
>> Stability is a really broad subject.
>>
>
>

[Eric Greenwell]

d b wrote:
> Do you include rudder lock as an instability? How about dynamic stability?
> What about downsprings, bob weights and other stability enhancement devices?
> Stability is a really broad subject.

Yes, it is. Interestingly, The one of the effects we've been discussing
- the stick force required at increasingly higher speeds - isn't really
an aircraft stability issue. It's a pilot control issue: the certifying
authorities believe an aircraft is easier to control if you have to push
on the stick to make it go faster, especially as you approach Vne. A
glider might still be pitch stable at high speeds, even though (as some
have reported) the stick force has decreased to zero. A lot of gliders
have an elevator with a concave (on the bottom) airfoil to provide this
increasing stick force.
--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[ADP]

I agree, I was only pointing out that there are certified aircraft that are
dynamically unstable in pitch (and roll and yaw) - for whatever reason.
The relevance had to do with the fact that the FAA or any certifying
authority, for that matter, can not necessarily be trusted
to keep one from getting into trouble should one operate outside design
parameters.
Sometimes such authorities restrict the CG range to keep aircraft within
design parameters, sometimes the restriction is with VNE and sometimes
the restrictions specify stick shakers, PICs and/or yaw dampers.

All of this leads up to the original purpose of the thread, how to avoid VNE
and do we really have to.

Cheers,

Allan

"Arnold Pieper" > wrote in message
om...
> Allan,
>
> I think we're generalizing too much here.
>
> The "distribution of forces on the wings change" as you posted, that is
> the
> key when you reach high speeds in sub-sonic aircraft.
> Supersonic aircraft have supercritical wing profiles and are a different
> story altogether.
>
......Snip.....

[Bill Daniels]

"Eric Greenwell" > wrote in message
...
> d b wrote:
> > Do you include rudder lock as an instability? How about dynamic
stability?
> > What about downsprings, bob weights and other stability enhancement
devices?
> > Stability is a really broad subject.
>
> Yes, it is. Interestingly, The one of the effects we've been discussing
> - the stick force required at increasingly higher speeds - isn't really
> an aircraft stability issue. It's a pilot control issue: the certifying
> authorities believe an aircraft is easier to control if you have to push
> on the stick to make it go faster, especially as you approach Vne. A
> glider might still be pitch stable at high speeds, even though (as some
> have reported) the stick force has decreased to zero. A lot of gliders
> have an elevator with a concave (on the bottom) airfoil to provide this
> increasing stick force.
> --
> -----
> change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA
>

I've been following this interesting thread.

On Thursday I had a nice flight out of Boulder, CO (USA). After cruising
the Continental Divide at 18,000 feet for several hours, I decided to test
the pitch stability of the Nimbus 2C near Vne after I descended below 10,000
feet.

The Nimbus 2C was flying with the CG at 80% aft and at a wing loading of 6.1
PSF confirmed by a recent weighing. This particular Nimbus has a separate
stabilizer and elevator and not the all-moving stab. The structure and
rigging has been checked by a well respected shop within the last year.

With the flaps in full negative, the big old glider easily accelerated to
Vne. As it accelerated, the elevator forces diminished as expected. At
Vne, the stick force per G was essentially zero signifying neutral or
slightly negative static stability. While controllable, and trim-able it
would diverge nose up or down with the slightest nudge.

This behavior was almost certainly unrelated to any wing twisting since the
carbon wings are extremely stiff. I suspect the airfoil is the root cause
since it has a particularly negative pitching moment. With the flaps in
full negative, the wings pitching moment is probably moved slightly toward
neutral stability where an unflapped glider would most likely exhibit more
negative pitching moment.

One easily forms the impression that flying this glider above Vne would be
most unwise. It's also very easy to see how a nervous pilot could get into
trouble at Vne since it requires a cool hand to fly it there. I am certain
that one unintended tug on the stick would send the G loading way above the
ultimate load factor in the blink of an eye. It makes me think that some of
the in-flight break-ups were overcontrol followed by G-LOC and then airframe
breakup

Seeing a pair of gliders circling about two miles ahead, I started the nose
up with a tiny bit of backpressure. The glider responded instantly and, to
prevent unintended G buildup, I needed to push slightly to control the
pitch-up until the IAS dropped below 110 knots where the control forces
became more normal.

I don't think this is particularly unusual behavior since it confirms what I
have seen on other high performance gliders. If you are going to fly near
Vne, do so with a cool hand and steady eye. It can get pretty unforgiving
up there.

Bill Daniels

[Eric Greenwell]

Bill Daniels wrote:

> I've been following this interesting thread.
>
> On Thursday I had a nice flight out of Boulder, CO (USA). After cruising
> the Continental Divide at 18,000 feet for several hours, I decided to test
> the pitch stability of the Nimbus 2C near Vne after I descended below 10,000
> feet.
>
> The Nimbus 2C was flying with the CG at 80% aft and at a wing loading of 6.1
> PSF confirmed by a recent weighing. This particular Nimbus has a separate
> stabilizer and elevator and not the all-moving stab. The structure and
> rigging has been checked by a well respected shop within the last year.

Is the elevator concave on the bottom side? If not, is it supposed to
be? Some people have filled in the concavity on their gliders (in
general, not the Nimbus 2 in particular) to decrease drag a bit.
>
> With the flaps in full negative, the big old glider easily accelerated to
> Vne. As it accelerated, the elevator forces diminished as expected. At
> Vne, the stick force per G was essentially zero signifying neutral or
> slightly negative static stability.

I'm not a real aerodyanicisit, but I don't think stick force is an
indicator of fixed-stick (while you are holding it) static stability.
This is determined by other factors, such as hinge placement, control
surface shape, trim springs, and probably other stuff.

> While controllable, and trim-able it
> would diverge nose up or down with the slightest nudge.

This is an indicator of static instability, if you mean "moving the
stick slightly forward leads to continually increasing airspeed". If the
airspeed increases some but then stabilizes, the glider is still
statically stable. "Stabilizes" has to be interpreted loosely, since
most gliders do have a long time constant (10-15 seconds) oscillation
that can be divergent.
>
> This behavior was almost certainly unrelated to any wing twisting since the
> carbon wings are extremely stiff. I suspect the airfoil is the root cause
> since it has a particularly negative pitching moment. With the flaps in
> full negative, the wings pitching moment is probably moved slightly toward
> neutral stability where an unflapped glider would most likely exhibit more
> negative pitching moment.
>
> One easily forms the impression that flying this glider above Vne would be
> most unwise. It's also very easy to see how a nervous pilot could get into
> trouble at Vne since it requires a cool hand to fly it there. I am certain
> that one unintended tug on the stick would send the G loading way above the
> ultimate load factor in the blink of an eye.

A cogent description of why I become nervous when people suggest
"pulling hard" over Vne.

> It makes me think that some of
> the in-flight break-ups were overcontrol followed by G-LOC and then airframe
> breakup

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Bill Daniels]

"Eric Greenwell" > wrote in message
...
> Bill Daniels wrote:
>
> > I've been following this interesting thread.
> >
> > On Thursday I had a nice flight out of Boulder, CO (USA). After
cruising
> > the Continental Divide at 18,000 feet for several hours, I decided to
test
> > the pitch stability of the Nimbus 2C near Vne after I descended below
10,000
> > feet.
> >
> > The Nimbus 2C was flying with the CG at 80% aft and at a wing loading of
6.1
> > PSF confirmed by a recent weighing. This particular Nimbus has a
separate
> > stabilizer and elevator and not the all-moving stab. The structure and
> > rigging has been checked by a well respected shop within the last year.
>
> Is the elevator concave on the bottom side? If not, is it supposed to
> be? Some people have filled in the concavity on their gliders (in
> general, not the Nimbus 2 in particular) to decrease drag a bit.

Very slight concavity. The apearance of the elevator as well as the
logbooks suggest that it has not been modified.

> >
> > With the flaps in full negative, the big old glider easily accelerated
to
> > Vne. As it accelerated, the elevator forces diminished as expected. At
> > Vne, the stick force per G was essentially zero signifying neutral or
> > slightly negative static stability.
>
> I'm not a real aerodyanicisit, but I don't think stick force is an
> indicator of fixed-stick (while you are holding it) static stability.
> This is determined by other factors, such as hinge placement, control
> surface shape, trim springs, and probably other stuff.
>
> > While controllable, and trim-able it
> > would diverge nose up or down with the slightest nudge.
>
> This is an indicator of static instability, if you mean "moving the
> stick slightly forward leads to continually increasing airspeed". If the
> airspeed increases some but then stabilizes, the glider is still
> statically stable. "Stabilizes" has to be interpreted loosely, since
> most gliders do have a long time constant (10-15 seconds) oscillation
> that can be divergent.

Obviously, with the glider at Vne, I'm not going to experiment with stick
free stability if I suspect the resulting behavior will be divergent.
However, once a nose-up input started the nose up and the airspeed down, it
appeared from the stick forces that the pitch rate was divergent above 110
knots. I detected no oscillatory behavior.

Don't confuse static and dynamic stability. All low drag gliders exhibit
dynamic instability (meaning they exhibit a phugoid oscillation and are, to
some degree, susceptible to PIO's) IF they are also statically stable. If
static stability is absent, then they will not also be dynamically unstable
since no restoring force exists to sustain the oscillation. (In my view
this is a damn good reason not to make gliders too statically stable.)

A glider with zero static stability will have zero stick force per G and no
tendency to hold any particular airspeed - elevator trim will be
unneccessary. It's easy to confuse this with stability since the glider
will not change its attitude very much in response to turbulence and no
phugiod will be evident. I actually prefer this since, to me at least, it
represents the lowest pilot workload.

> >
> > This behavior was almost certainly unrelated to any wing twisting since
the
> > carbon wings are extremely stiff. I suspect the airfoil is the root
cause
> > since it has a particularly negative pitching moment. With the flaps in
> > full negative, the wings pitching moment is probably moved slightly
toward
> > neutral stability where an unflapped glider would most likely exhibit
more
> > negative pitching moment.
> >
> > One easily forms the impression that flying this glider above Vne would
be
> > most unwise. It's also very easy to see how a nervous pilot could get
into
> > trouble at Vne since it requires a cool hand to fly it there. I am
certain
> > that one unintended tug on the stick would send the G loading way above
the
> > ultimate load factor in the blink of an eye.
>
> A cogent description of why I become nervous when people suggest
> "pulling hard" over Vne.
>
> > It makes me think that some of
> > the in-flight break-ups were overcontrol followed by G-LOC and then
airframe
> > breakup
>

Should I ever find myself over Vne in a dive. First, if no essential parts
of the glider had departed so far, I would assume that they would not as
long as the airspeed didn't increase further and the G loads remained low.
If there were any rolling/turning I would stop that with aileron and then,
with ailerons neutral, I would use the smallest up elevator input possible
that would start the airspeed on a decreasing trend. As the airspeed
decreased, I would progressively add further tiny up inputs to ever so
slightly increase the G loading and accelerate the rate of airspeed
decrease. Once the dive angle was less than about 50 degrees, the airspeed
should be approaching Vne and I would increase the load on the wings
judiciously to recover from the dive as quickly as possible.

If the glider had conventional plug-type spoilers, I would refrain from
using them until under Va. If it had trailing edge air brakes, as the
Nimbus 2C has, I would probably use them on a situational basis.

If, in the above scenario, it appeared that the trajectory would intersect
the ground, it would be a good time to think (damn quickly) about the
parachute.

Bill Daniels

[Arnold Pieper]

> With the flaps in full negative, the big old glider easily accelerated to
> Vne. As it accelerated, the elevator forces diminished as expected. At
> Vne, the stick force per G was essentially zero signifying neutral or
> slightly negative static stability. While controllable, and trim-able it
> would diverge nose up or down with the slightest nudge.
>

"The elevator forces diminished as expected"...
I don't know why you expected this behaviour, since this goes against
certification requirements and against normal flight behaviour.
None of the gliders and aircraft that I've flown in the past 24 years
present this characteristic.

The certification requirements (both JAR and FAR), spell out that stick
forces have to increase with increasing G-loads, all the way to VNE.
Static stability requiremens for certification say that the airspeed has to
return to within 15% (10% in the case of FARs) of trimmed speed, for all
trimmable speeds between stall speed and VNE, and any significant change in
airspeed HAS TO cause a variation in stick force plainly percepbible to the
pilot.

JAR-22 says about Dynamic Stability that "any short period oscillations
between Stall Speed and Vdf must be heavily damped" with the primary
controls both free and fixed. Vdf is the demonstrated design speed, VNE is
90% of Vdf.

[Arnold Pieper]

>
> Concorde, when it was acelaring through transonic speeds had to do a
> large fuel xfer to the aft tanks to conpensate for the strong nose
> down trim shift.
>
> It was rumoured to be certified :)

I've already written about this : in a supercritical airfoil (read
supersonic design) the Aerodynamic center does move back as the speed goes
ABOVE MACH 1.
Also, delta-wings tend to be challenging to manage in terms of CofG, so,
they usually require some form of fuel xfr to keep'em in balance.
Classic example is the british Vulcan bomber, that required substantial
amounts of weight (30 tons come to mind) just to be in balance...

So these will become issues when we start flying supersonic gliders with
delta-wings...
Maybe the space-shuttle pilots out there can share their views.

[Bill Daniels]

"Arnold Pieper" > wrote in message
. com...
>
> > With the flaps in full negative, the big old glider easily accelerated
to
> > Vne. As it accelerated, the elevator forces diminished as expected. At
> > Vne, the stick force per G was essentially zero signifying neutral or
> > slightly negative static stability. While controllable, and trim-able
it
> > would diverge nose up or down with the slightest nudge.
> >
>
> "The elevator forces diminished as expected"...
> I don't know why you expected this behaviour, since this goes against
> certification requirements and against normal flight behaviour.
> None of the gliders and aircraft that I've flown in the past 24 years
> present this characteristic.

I bet they did, you just mis-identified it. If you think the elevator gets
stiffer as the airspeed increases and more stick force per G is required,
I'd have to conclude you haven't flown many gliders fast. In fact, at Vne,
very tiny stick forces will produce large G forces.
>
> The certification requirements (both JAR and FAR), spell out that stick
> forces have to increase with increasing G-loads, all the way to VNE.

I didn't say that the stick forces wouldn't have increased with increasing G
loads. I didn't test this. The flight was kept very close to 1.0G. BTW, I
didn't say the Nimbus 2C is standard category either, it's experimental, at
least in the USA.

> Static stability requiremens for certification say that the airspeed has
to
> return to within 15% (10% in the case of FARs) of trimmed speed, for all
> trimmable speeds between stall speed and VNE, and any significant change
in
> airspeed HAS TO cause a variation in stick force plainly percepbible to
the
> pilot.

If the airspeed returns to the trimmed airspeed but doesn't stabilize there
does it pass the test? Apparently, yes. No glider will stabilize itself at
the trimmed airspeed because the phugoid is undamped. It will oscillate
around the trimmed airspeed with ever increasing amplitude.

The problem with gliders is that, with highly cambered airfoils, the center
of lift moves aft with increasing airspeed (decreasing AOA) or, put another
way, the airfoil generates a nose down torque about the lateral axis with
increasing airspeed. This nose down torque opposes the nose up trimming
forces required for static stability. This diminishes the static stability
margin as airspeed increases.

If the trimming system is weak, as with a bungee spring, the nose down
pitching moment will overcome the spring at some high airspeed and the nose
will want to continue down unless the pilot intercedes. (Divergence)

I have no trouble believing the stories about uncontrollable vertical dives.
The nose down pitching moment created by the airfoil is very likely
powerful enough on some gliders to completely overcome the up elevator
authority at some speed above Vne.

>
> JAR-22 says about Dynamic Stability that "any short period oscillations
> between Stall Speed and Vdf must be heavily damped" with the primary
> controls both free and fixed. Vdf is the demonstrated design speed, VNE is
> 90% of Vdf.
>
The key here is "short period oscillations", i.e. 1 - 2Hz, not 15 - 20
second phugoid oscillations. NO high performance glider has a damped
phugoid - period. The only way a phugoid is damped is with drag and, by
definition, a high performance glider has little drag.

Take any glider and trim it for best L/D, then push it up to 10 Knots above
best L/D and release the stick. The pitch oscillations will increase in
amplitude until you take control again. This is true whether the stick is
free or fixed. To demonstrate the drag effect, just open the spoilers and
watch the phugoid damp out.

Bill Daniels

[JJ Sinclair]

I got a question for you aerodynamasists (is that a word?)

When Schleicher added a bit to the wing span of the ASH-25 (25 m to 26.5m) they
required that 3 Kg of lead be mounted in the leading edge (inside the D tube)
it was to be spread down the D tube for about 10 feet and then glassed in
place.

Why? and why in the leading edge?
JJ Sinclair

[Udo Rumpf]

> The Nimbus 2C was flying with the CG at 80% aft and at a wing loading of
6.1
> PSF confirmed by a recent weighing. This particular Nimbus has a separate
> stabilizer and elevator and not the all-moving stab. The structure and
> rigging has been checked by a well respected shop within the last year.
>
> With the flaps in full negative, the big old glider easily accelerated to
> Vne. As it accelerated, the elevator forces diminished as expected. At
> Vne, the stick force per G was essentially zero signifying neutral or
> slightly negative static stability. While controllable, and trim-able it
> would diverge nose up or down with the slightest nudge.
>
> This behavior was almost certainly unrelated to any wing twisting since
the
> carbon wings are extremely stiff. I suspect the airfoil is the root cause
> since it has a particularly negative pitching moment. With the flaps in
> full negative, the wings pitching moment is probably moved slightly toward
> neutral stability where an unflapped glider would most likely exhibit more
> negative pitching moment.
>
> One easily forms the impression that flying this glider above Vne would be
> most unwise. It's also very easy to see how a nervous pilot could get
into
> trouble at Vne since it requires a cool hand to fly it there. I am
certain
> that one unintended tug on the stick would send the G loading way above
the
> ultimate load factor in the blink of an eye. It makes me think that some
of
> the in-flight break-ups were overcontrol followed by G-LOC and then
airframe
> breakup
>
> Seeing a pair of gliders circling about two miles ahead, I started the
nose
> up with a tiny bit of backpressure. The glider responded instantly and,
to
> prevent unintended G buildup, I needed to push slightly to control the
> pitch-up until the IAS dropped below 110 knots where the control forces
> became more normal.
>
> I don't think this is particularly unusual behavior since it confirms what
I
> have seen on other high performance gliders. If you are going to fly near
> Vne, do so with a cool hand and steady eye. It can get pretty unforgiving
> up there.
>
> Bill Daniels

Bill
I fly my glider the same way, with The C of G way back
What you are describing shows your glider is tuned just right if your
horizontal
stab / elevator if it has no concave.
The FX 67 shows a centre of pressure of about 38%MAC at Cl of .2 with
a minus 8 deg flap. With an extra -2 deg deflection the CofP will move
further forward ahead of the CofG. At that speed and - 10 deg. flap
the nose should come up gently.

As for the concaved elevator,
if one runs out of nose down trim and one has to hold the stick still hard
forward to maintain high speed, as on a ridge or in very strong
conditions, the concave on the stab acts like a servo tab and could in fact
contribute to a sudden pitch up at high speed if one is inattentive for a
second.

As for VNE and recovery, I had one unintended spin entries in my glider,
caused by an avoidance manoeuvre. I was banked about 35 deg when an other
glider was heading toward me. If it would have been one second later the
glider would have been in a blind spot. I cranked the glider over still
further ( instead of pushing down hard) and the outside wing stalled due to
more
aileron input and tightening up the circle. I found myself vertical in a
fraction of a second. I neutralized the stick and started recovery just a
bit to soon
I had a small secondary stall, after that the nose came up gently the
recovery was
completed in about 500ft that included the pull up to bleed off the extra
speed. The recovery may in fact have taken 600 ft. The maximum speed was
about 115 kt. No spoilers where used. (I have no spoilers). I like to think
because I was
exposed to unusual and sudden attitudes early on in my flying, things went
smoothly.
The altitude was 3000ft.

Regards
Udo

[Eric Greenwell]

Bill Daniels wrote:

> The problem with gliders is that, with highly cambered airfoils, the center
> of lift moves aft with increasing airspeed (decreasing AOA) or, put another
> way, the airfoil generates a nose down torque about the lateral axis with
> increasing airspeed.

From my reading of "Fundamentals of Sailplane Design", the center of
lift remains constant (by definition), as does the pitching moment
coefficient (by measurement on a typical airfoil), with AOA. This is for
a _fixed_ airfoil. The pitching _moment_ will increase with speed (even
though the coefficient doesn't), of course.

> This nose down torque opposes the nose up trimming
> forces required for static stability. This diminishes the static stability
> margin as airspeed increases.

This is were I get puzzled: you were flying the glider with negative
flap, which changes the airfoil to one with a positive pitching moment.
Shouldn't this increase, rather than diminish, the static stability?
>
> If the trimming system is weak, as with a bungee spring, the nose down
> pitching moment will overcome the spring at some high airspeed and the nose
> will want to continue down unless the pilot intercedes. (Divergence)
>
> I have no trouble believing the stories about uncontrollable vertical dives.
> The nose down pitching moment created by the airfoil is very likely
> powerful enough on some gliders to completely overcome the up elevator
> authority at some speed above Vne.

This might be true with a positive cambered airfoil, but during the
flight test you did with your Nimbus, you used a negatively cambered
airfoil.


--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Bill Daniels]

"Eric Greenwell" > wrote in message
...
> Bill Daniels wrote:
>
> > The problem with gliders is that, with highly cambered airfoils, the
center
> > of lift moves aft with increasing airspeed (decreasing AOA) or, put
another
> > way, the airfoil generates a nose down torque about the lateral axis
with
> > increasing airspeed.
>
> From my reading of "Fundamentals of Sailplane Design", the center of
> lift remains constant (by definition), as does the pitching moment
> coefficient (by measurement on a typical airfoil), with AOA. This is for
> a _fixed_ airfoil. The pitching _moment_ will increase with speed (even
> though the coefficient doesn't), of course.
>
> > This nose down torque opposes the nose up trimming
> > forces required for static stability. This diminishes the static
stability
> > margin as airspeed increases.
>
> This is were I get puzzled: you were flying the glider with negative
> flap, which changes the airfoil to one with a positive pitching moment.
> Shouldn't this increase, rather than diminish, the static stability?
> >
> > If the trimming system is weak, as with a bungee spring, the nose down
> > pitching moment will overcome the spring at some high airspeed and the
nose
> > will want to continue down unless the pilot intercedes. (Divergence)
> >
> > I have no trouble believing the stories about uncontrollable vertical
dives.
> > The nose down pitching moment created by the airfoil is very likely
> > powerful enough on some gliders to completely overcome the up elevator
> > authority at some speed above Vne.
>
> This might be true with a positive cambered airfoil, but during the
> flight test you did with your Nimbus, you used a negatively cambered
> airfoil.

> change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA
>

You're right, the negative flaps would tend to reduce the airfoils nose down
pitching moment and increase the static stability. My feeling is that the
effect of just 7 degrees of negative flap just isn't enough to negate the
whole wings' pitching moment.

Bill Daniels

[Bill Daniels]

"JJ Sinclair" > wrote in message
...
> I got a question for you aerodynamasists (is that a word?)
>
> When Schleicher added a bit to the wing span of the ASH-25 (25 m to 26.5m)
they
> required that 3 Kg of lead be mounted in the leading edge (inside the D
tube)
> it was to be spread down the D tube for about 10 feet and then glassed in
> place.
>
This is a guess, but I think their concern might have been about the wing
having a tendency to twist leading edge up in a high G pull-up. If I
recall, this is called a divergent bending moment. It's more commonly found
on swept forward wings. The lead in the LE would tend to counteract that.

As I say, only a guess.

Bill Daniels

[Michael McNulty]

"JJ Sinclair" > wrote in message
...
> I got a question for you aerodynamasists (is that a word?)
>
> When Schleicher added a bit to the wing span of the ASH-25 (25 m to 26.5m)
they
> required that 3 Kg of lead be mounted in the leading edge (inside the D
tube)
> it was to be spread down the D tube for about 10 feet and then glassed in
> place.
>
> Why? and why in the leading edge?
> JJ Sinclair

To prevent flutter

[Eric Greenwell]

Bill Daniels wrote:

> "Eric Greenwell" > wrote in message
> ...
>
>>Bill Daniels wrote:
>>
>>
>>>The problem with gliders is that, with highly cambered airfoils, the
>
> center
>
>>>of lift moves aft with increasing airspeed (decreasing AOA) or, put
>
> another
>
>>>way, the airfoil generates a nose down torque about the lateral axis
>
> with
>
>>>increasing airspeed.
>>
>> From my reading of "Fundamentals of Sailplane Design", the center of
>>lift remains constant (by definition), as does the pitching moment
>>coefficient (by measurement on a typical airfoil), with AOA. This is for
>>a _fixed_ airfoil. The pitching _moment_ will increase with speed (even
>>though the coefficient doesn't), of course.
>>
>>
>>> This nose down torque opposes the nose up trimming
>>>forces required for static stability. This diminishes the static
>
> stability
>
>>>margin as airspeed increases.
>>
>>This is were I get puzzled: you were flying the glider with negative
>>flap, which changes the airfoil to one with a positive pitching moment.
>>Shouldn't this increase, rather than diminish, the static stability?
>>
>>>If the trimming system is weak, as with a bungee spring, the nose down
>>>pitching moment will overcome the spring at some high airspeed and the
>
> nose
>
>>>will want to continue down unless the pilot intercedes. (Divergence)
>>>
>>>I have no trouble believing the stories about uncontrollable vertical
>
> dives.
>
>>>The nose down pitching moment created by the airfoil is very likely
>>>powerful enough on some gliders to completely overcome the up elevator
>>>authority at some speed above Vne.
>>
>>This might be true with a positive cambered airfoil, but during the
>>flight test you did with your Nimbus, you used a negatively cambered
>>airfoil.
>
>
>>change "netto" to "net" to email me directly
>>
>>Eric Greenwell
>>Washington State
>>USA
>>
>
>
> You're right, the negative flaps would tend to reduce the airfoils nose down
> pitching moment and increase the static stability. My feeling is that the
> effect of just 7 degrees of negative flap just isn't enough to negate the
> whole wings' pitching moment.

Your feeling is probably right. I just found the pitching moment diagram
for the FX 67-K-150 airfoil (FOSD, page 93), which is used on the outer
part of the wing of the Nimbus II. At -8 deg deflection, it is very
close to zero, but still negative. I'm assuming the FX 67-170 airfoil
for the inner part of the wing is very similar.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[Bill Daniels]

> > You're right, the negative flaps would tend to reduce the airfoils nose
down
> > pitching moment and increase the static stability. My feeling is that
the
> > effect of just 7 degrees of negative flap just isn't enough to negate
the
> > whole wings' pitching moment.
>
> Your feeling is probably right. I just found the pitching moment diagram
> for the FX 67-K-150 airfoil (FOSD, page 93), which is used on the outer
> part of the wing of the Nimbus II. At -8 deg deflection, it is very
> close to zero, but still negative. I'm assuming the FX 67-170 airfoil
> for the inner part of the wing is very similar.
>
> --
> -----
> change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA
>

Of course, we're dealing with the whole glider, not just the wing, and that
means down wash effects on the stab, stab/elevator section, trim bungee
spring rates, 3D flow around the fuselage, etc.. all summed together in the
static stability equation.

You know, proof reading the preceding paragraph makes me think about that
screen door spring thingy connected to the green knob that's pretending to
be a trim bungee. I suppose those things get old and weak. I wonder what
effect that would have....

Bill Daniels

[Arnold Pieper]

It seems like there is a fixation on the "negative pitching moment",
forgetting the global forces acting on the glider.
The CG is ahead of the Aerodynamic Center of the wing, and thus generates a
nose down moment that is counteracted by the horizontal stabilizer.
For practical purposes, the Aerodynamic Center does not change with AOA (or
speed), and it is what is utilized to analyze stability.
I'll say that again : For stability analysis, the AC does not change (check
FOSD or similar publication).

The balance of forces between the CG, wing (AC) and the horizontal
stabilizer is such that the glider tends to stay at the trimmed airspeed,
from stall speed all the way to Vne. It MUST be so, and it has to be
demonstrated to be so under all conditions of CG position (always ahead of
the AC) and all airspeeds, from stall to redline.
"The speed must settle within 15% of trimmed airspeed"... etc.

As far as the stick forces increasing with airspeed, it must be this way or
we simply wouldn't need a pitch trim control.
The JARs and FARs don't really require a pitch trim control, if the stick
forces are light enough to hand fly stable in all possible speeds in the
envelope, and the "trimmed speed" is 1.4 or 1.5 the speed of stall (can't
remember exactly), which means, if the stick is released, the speed has to
settle on 1.4 or 1.5 the stall speed.
I've never flown a glider or airplane that doesn't have a pitcth trim
control, so, that speaks for itself.
But always, the stick forces must be progressive and perceptibly so.

If the negative pitching moment was this big monster you seem to think it
is, VNE wouldn't be determined by VD or structural design speed.
It would be determined by when we run out of "nose up" force on the elevator
and go into the infinite inverted outside loop mode, which has never been
heard of. Frankly, that must have come from someone who hadn't finished
reading the whole aerodynamic book yet, and started jumping to conclusions.

We usually run out of "Nose down" trim, at very high speeds, and have to use
some "push forward" force on the stick to maintain the high speed and
prevent the nose from coming up too quickly, such as when I want to recover
from a high speed dive or a low pass, high speed finish.

A divergent mode is unstable and therefore unacceptable for the europeans
and americans.



"Bill Daniels" > wrote in message
news:dKLbc.174977$1p.2106507@attbi_s54...
> > > You're right, the negative flaps would tend to reduce the airfoils
nose
> down
> > > pitching moment and increase the static stability. My feeling is that
> the
> > > effect of just 7 degrees of negative flap just isn't enough to negate
> the
> > > whole wings' pitching moment.
> >
> > Your feeling is probably right. I just found the pitching moment diagram
> > for the FX 67-K-150 airfoil (FOSD, page 93), which is used on the outer
> > part of the wing of the Nimbus II. At -8 deg deflection, it is very
> > close to zero, but still negative. I'm assuming the FX 67-170 airfoil
> > for the inner part of the wing is very similar.
> >
> > --
> > -----
> > change "netto" to "net" to email me directly
> >
> > Eric Greenwell
> > Washington State
> > USA
> >
>
> Of course, we're dealing with the whole glider, not just the wing, and
that
> means down wash effects on the stab, stab/elevator section, trim bungee
> spring rates, 3D flow around the fuselage, etc.. all summed together in
the
> static stability equation.
>
> You know, proof reading the preceding paragraph makes me think about that
> screen door spring thingy connected to the green knob that's pretending to
> be a trim bungee. I suppose those things get old and weak. I wonder what
> effect that would have....
>
> Bill Daniels
>

[Andreas Maurer]

On Sun, 04 Apr 2004 00:06:23 GMT, "Bill Daniels" >
wrote:

> No glider will stabilize itself at
>the trimmed airspeed because the phugoid is undamped. It will oscillate
>around the trimmed airspeed with ever increasing amplitude.

I think things are getting esoteric now. ;)
I've flown about 40 kinds of gliders so far, an ALL of the stabilized
at the trimmed airspeed within a couple of oscillations. None was
showing the behaviour that you describe.
What am I doing wrong? ;)




>I have no trouble believing the stories about uncontrollable vertical dives.
>The nose down pitching moment created by the airfoil is very likely
>powerful enough on some gliders to completely overcome the up elevator
>authority at some speed above Vne.

Well... it's simple: If you are flying faster than Vne, you become a
test pilot. But staying below Vne is extremely simple in a glider...



>Take any glider and trim it for best L/D, then push it up to 10 Knots above
>best L/D and release the stick. The pitch oscillations will increase in
>amplitude until you take control again. This is true whether the stick is
>free or fixed. To demonstrate the drag effect, just open the spoilers and
>watch the phugoid damp out.

Hmmm... is it possible that you are flying with an extremely aft CG?


Bye
Andreas

[Andreas Maurer]

On 04 Apr 2004 00:27:33 GMT, (JJ Sinclair) wrote:

>I got a question for you aerodynamasists (is that a word?)
>
>When Schleicher added a bit to the wing span of the ASH-25 (25 m to 26.5m) they
>required that 3 Kg of lead be mounted in the leading edge (inside the D tube)
>it was to be spread down the D tube for about 10 feet and then glassed in
>place.
>
>Why? and why in the leading edge?

To change the flutter frequency of the wing.

It's problematic if the natural oscillation frequency of the controls
and the part the control is mounted on (elevator/ rudder and fuselage,
airleron/flaps and wing) is similar.

If natural oscillation frequencies are similar, an oscillation that is
started on a certain part might cause other parts to ascillate in
harmony - therefore changing the weight or CG of a part is used to
make sure that each moving part has a different oscillation frequency.



Bye
Andreas

[Bill Daniels]

"Andreas Maurer" > wrote in message
...
> On Sun, 04 Apr 2004 00:06:23 GMT, "Bill Daniels" >
> wrote:
>
> > No glider will stabilize itself at
> >the trimmed airspeed because the phugoid is undamped. It will oscillate
> >around the trimmed airspeed with ever increasing amplitude.
>
> I think things are getting esoteric now. ;)
> I've flown about 40 kinds of gliders so far, an ALL of the stabilized
> at the trimmed airspeed within a couple of oscillations. None was
> showing the behaviour that you describe.
> What am I doing wrong? ;)

Flying very low preformance gliders or flying with the spoilers open?

>
> Hmmm... is it possible that you are flying with an extremely aft CG?
>
If the CG were aft, then it wouldn't have a restoring force and so wouldn't
oscillate. It's when the CG is toward the forward limit that the
oscillation is worse.

Bill Daniels

[d b]

My Mosquito has a long term phugoid. Try this. Get everything just
perfect. In trim, stable on airspeed, then let go of the stick for 10 minutes.
If it wanders off the trimmed speed, then corrects but overshoots, you
have a long term phugoid. If it eventually diminishes, it's damped. Most
pilots never notice a long term phugoid. The air is seldom smooth enough.

In article >, Andreas Maurer
> wrote:
>On Sun, 04 Apr 2004 00:06:23 GMT, "Bill Daniels" >
>wrote:
>
>> No glider will stabilize itself at
>>the trimmed airspeed because the phugoid is undamped. It will oscillate
>>around the trimmed airspeed with ever increasing amplitude.
>
>I think things are getting esoteric now. ;)
>I've flown about 40 kinds of gliders so far, an ALL of the stabilized
>at the trimmed airspeed within a couple of oscillations. None was
>showing the behaviour that you describe.
>What am I doing wrong? ;)
>
>
>
>
>>I have no trouble believing the stories about uncontrollable vertical dives.
>>The nose down pitching moment created by the airfoil is very likely
>>powerful enough on some gliders to completely overcome the up elevator
>>authority at some speed above Vne.
>
>Well... it's simple: If you are flying faster than Vne, you become a
>test pilot. But staying below Vne is extremely simple in a glider...
>
>
>
>>Take any glider and trim it for best L/D, then push it up to 10 Knots above
>>best L/D and release the stick. The pitch oscillations will increase in
>>amplitude until you take control again. This is true whether the stick is
>>free or fixed. To demonstrate the drag effect, just open the spoilers and
>>watch the phugoid damp out.
>
>Hmmm... is it possible that you are flying with an extremely aft CG?
>
>
>Bye
>Andreas

[Andreas Maurer]

On Sun, 04 Apr 2004 20:43:19 GMT, "Bill Daniels" >
wrote:

>> What am I doing wrong? ;)
>
>Flying very low preformance gliders or flying with the spoilers open?
Neither, nor. Nearly all of these gliders have an L/D between 40 and
60.


>> Hmmm... is it possible that you are flying with an extremely aft CG?
>>
>If the CG were aft, then it wouldn't have a restoring force and so wouldn't
>oscillate. It's when the CG is toward the forward limit that the
>oscillation is worse.

Never notived that (my CG is very forward if I don't have water/lead
in the tail). The phugoid is always there, and is always (nearly)
dampened away after a number of oscillations.

Bye
Andreas

[Denis]

d b wrote:

> You got it. Stability isn't really defined as the aerodynamics of the plane.
> It is defined as what the pilot sees. You didn't mention that
> dynamic instability is quite common and is usually not a serious issue.

???

I think you are mixing it all...

Stability *is* defined by aerodynamics and is quite difficult for a non
specialist pilot to determine...

*Dynamic* instability is very serious and may result in a loss of
control (pilot induced oscillations) and/or overloading

*Static* instability in not a serious issue as long the glider remains
dynamically stable, which is the case except with very static-unstable
designs - but it should not be "quite common" because the certification
standards do require a positive static stability (whether this
requirement is pertinent or not is another debate)


> In article >, "Arnold Pieper"
> > wrote:
>
>>But aircraft need to have a predictable behaviour and a predictable response
>>to control inputs.

Unstable aircraft have a very predictable unstable behaviour ;-)

And unstability (either static or dynamic) does not mean that control
inputs response (at least in its primary effect) is inverted...


--
Denis

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

[Mark James Boyd]

I thought the BRS parachutes were a good idea, and
maybe they still are, but from a short visit to tehachapi
and seeing the HP-24 being made, and talking to the
fiberglass guy, he said that putting a big hole in
the fuselage requires a bit of work (and weight)
to restrengthen.

I still find it an elegant system, but I have no info
on how making that big hole allows twisting or causes
cracks later. I suppose the motorglider
guys would know more about it...

I am quite happy that the Russia and Sparrowhawk
offer BRS as an option. It will be interesting to
see any "saves" in these, and if this favorably
affects insurance enough that the insurers give a rate
discount for this device...
--

------------+
Mark Boyd
Avenal, California, USA

[Denis]

Bill Daniels wrote:

> A glider with zero static stability will have zero stick force per G and no
> tendency to hold any particular airspeed - elevator trim will be
> unneccessary. It's easy to confuse this with stability since the glider
> will not change its attitude very much in response to turbulence and no
> phugiod will be evident. I actually prefer this since, to me at least, it
> represents the lowest pilot workload.

I agree - except for "zero stick force per G"... the force per G is a
dynamic behaviour and not static. If you have zero static stability
(which is, as you said, the situation where the position of the stick
at 1 G is the same at different speeds) you still have a positive
dynamic stability (therefore a positive, though perhaps very light,
"force per G") because of the moment induced by pitching speed...


--
Denis

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

[Denis]

Arnold Pieper wrote:

> "The elevator forces diminished as expected"...
> I don't know why you expected this behaviour, since this goes against
> certification requirements and against normal flight behaviour.
> None of the gliders and aircraft that I've flown in the past 24 years
> present this characteristic.

What's your weight ?

> The certification requirements (both JAR and FAR), spell out that stick
> forces have to increase with increasing G-loads, all the way to VNE.
> Static stability requiremens for certification say that the airspeed has to
> return to within 15% (10% in the case of FARs) of trimmed speed, for all
> trimmable speeds between stall speed and VNE, and any significant change in
> airspeed HAS TO cause a variation in stick force plainly percepbible to the
> pilot.

The rules are there to be transgressed - either by older gliders
(grandfather right) or because some design may get derogations to these
rules in the certification process


> JAR-22 says about Dynamic Stability that "any short period oscillations
> between Stall Speed and Vdf must be heavily damped" with the primary
> controls both free and fixed. Vdf is the demonstrated design speed, VNE is
> 90% of Vdf.

May you please recall us how long is a period of a "short-period
oscillation" on a glider ?


--
Denis

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

[Denis]

Arnold Pieper wrote:

> The CG is ahead of the Aerodynamic Center of the wing

No ;-)

Although this is one of the most common misconception it's not true.
Except at very forward CG position, the glider CG is *behind* the
aerodynamic center of the wing.

If you don't believe me, check the CG range on your flight manual. And
compare with the mean aerodynamic chord (the aerodynamic center in all
common profiles is at 25% of the chord)

> Frankly, that must have come from someone who hadn't finished
> reading the whole aerodynamic book yet, and started jumping to conclusions.

You perhaps read the whole book, but unfortunately many books are wrong
(especially those destined to student pilots), in an effort to explain
the stability issue simplier, pretending that the CG must be ahead of
the wing AC...

Anyway we are well out of the subject of this thread ;-)

--
Denis

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

[Denis]

Paul Repacholi wrote:

> Concorde, when it was acelaring through transonic speeds had to do a
> large fuel xfer to the aft tanks to conpensate for the strong nose
> down trim shift.
>
> It was rumoured to be certified :)

Surprisingly... but I'm confident that, had the soaring price of oil in
the 70's not succeeded in killing commercially this beautiful bird, the
FAA would not have been so kind to let it fly over the USA with such a
dangerous feature ;-)

--
Denis

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

[Arnold Pieper]

Denis,

Since you're not helping move things in the right direction, I'll explain it
in a bit more detail.

I referred to the Aerodynamic Center, which applies to the isolated wing
analysis, because people were referring to the Center of Pressure, that also
applies to the isolated wing analysis.
The AC does not move, the CP does, however, is the AC that is used for
stability analysis, not the CP.

Anyway :
When you consider the glider as a whole, as opposed to the isolated wing,
there is something called the "Neutral Point", which is the point where the
Lift vector acts considering all aerodynamic forces acting on the glider,
and it too does not move with AOA.
The CG must be always ahead of this Neutral Point, and the Horizontal
Stabilizer/elevator is what keeps them balanced.


"Denis" > wrote in message
...
> Arnold Pieper wrote:
>
> > The CG is ahead of the Aerodynamic Center of the wing
>
> No ;-)
>
> Although this is one of the most common misconception it's not true.
> Except at very forward CG position, the glider CG is *behind* the
> aerodynamic center of the wing.
>
> If you don't believe me, check the CG range on your flight manual. And
> compare with the mean aerodynamic chord (the aerodynamic center in all
> common profiles is at 25% of the chord)
>
> > Frankly, that must have come from someone who hadn't finished
> > reading the whole aerodynamic book yet, and started jumping to
conclusions.
>
> You perhaps read the whole book, but unfortunately many books are wrong
> (especially those destined to student pilots), in an effort to explain
> the stability issue simplier, pretending that the CG must be ahead of
> the wing AC...
>
> Anyway we are well out of the subject of this thread ;-)
>
> --
> Denis
>
> R. Parce que ça rompt le cours normal de la conversation !!!
> Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?

[Denis]

Arnold Pieper wrote:

> When you consider the glider as a whole, as opposed to the isolated wing,
> there is something called the "Neutral Point", which is the point where the
> Lift vector acts considering all aerodynamic forces acting on the glider,
> and it too does not move with AOA.
> The CG must be always ahead of this Neutral Point, and the Horizontal
> Stabilizer/elevator is what keeps them balanced.

Yes. Now I better agree ;-)

The CG must be always ahead of this Neutral Point (the whole glider
Aerodynamic Center) - although the CG may be *behind* the Aerodynamic
Center of the wing (and is actually behind, except in far forward CG
position - or in tailless designs)

--
Denis

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

[F.L. Whiteley]

http://www.jaa.nl/section1/jars/445499.pdf

JAR 22.73 Descent, high speed
It must be shown that the sailplane with the
airbrakes extended, will not exceed VNE in a
dive at an angle to the horizon of:
(a) 45° when the sailplane is approved for
cloud flying and/or aerobatics when certificated
in the Aerobatic or Utility Category;
(b) .

Don't know how many sailplanes may be built to para b. Guess I assumed all
JAR22 aircraft were designed to para a standards.

I believe this resulted from the supposedly demonstrated difficulty in
maintaining a vertical descent, even in cloud, as a result of some empirical
testing about 40 years ago. At least that's what I recall from
conversations in the '70s.

If you want vertical limiting airbrakes, I know where you can buy a
Schweizer 1-34;^)

Frank Whiteley

"Arnold Pieper" > wrote in message
om...
> The glider won't stay at 90 degrees nose down like I said. As it
accelerate
> it will bring the nose up.
> That in itself is no guarantee you won't reach VNE before long, of course,
> so you have to control the recovery.
> Avoid reaching VNE by deploying the airbrakes if you see the speed
> increasing too fast, as I said, controlling the dive.
> That is always better than trying to bend the wings by pulling too many
Gs.
> Your attitude will be at 45 degrees or less in a matter of seconds, and at
> that attitude, the airbrakes will prevent the overspeed or at least
minimize
> the condition (if they were deployed too late).
>
> You can go over VNE if you don't deploy the airbrakes and just try to
> "G-load" your way out of such a high-speed dive,and that's the condition
in
> which you overstress the structure, produce internal cracks, bend or
damage
> some of the hardware in the control system.
> That's the reason you should watch the airspeed and deploy the airbrakes
in
> time (before reaching VNE).
>
> Don't be affraid to open the airbrakes at high speed, believe me, the
> manufacturer is just a little smarter than that.
> You have to be careful at high speed just because they tend to jump out
more
> easily, so, have a firm hand on it.
>
> Real aerobatic training (as opposed to some occasional loops) will clarify
a
> lot of this.
>
>
> "Todd Pattist" > wrote in message
> ...
> > "Arnold Pieper" > wrote:
> >[i]
> > >Maybe true if "near vertical", however, staying at a near vertical dive
> is
> > >something that requires a conscient effort.
> > >The glider won't just stay there on its own.
> > >To remain in a 90 degree vertical dive requires a significant amount of
> > >forward stick force and concentration.
> > >As speed increases, the nose will come up (away from vertical) even if
> you
> > >don't want it to, and even with full forward trim, it would still
require
> an
> > >honest push on the stick to maintain that attitude.
> >
> > All of this is true, but it's not relevant to whether the
> > airbrakes of a modern glider are speed limiting. They
> > aren't. There are lots of initial conditions that will
> > exceed Vne with the brakes out.
> >
> > >If you're recovering from an unusual attitude that puts you in a near
> > >vertical dive, just don't sweat it.
> > >Open the airbrakes and slowly pull out of the dive. There is no need to
> > >overstress.
> >
> > There is also no guarantee that you will not exceed Vne or
> > that your final speed will be lower than someone who applies
> > a higher AOA with it's higher G-load and reduces the descent
> > angle more quickly.
> >
> > >If you want to feel safer, go for aerobatic training.
> > >You will see that you can actually dive 90 degrees down and recover
> without
> > >exceeding VNE, without using the airbrakes and not getting even close
to
> G
> > >limits.
> >
> > I do loops often. Slow and vertical is far different from
> > fast and vertical.
> >
> >
> > Todd Pattist - "WH" Ventus C
> > (Remove DONTSPAMME from address to email reply.)
>
>

[F.L. Whiteley]

The Type Certificate is Glider Utility Category for the Duo Discus, which
would seem to be inappropriate given the 45degree requirement of
JAR22.73(a), unless this was subject to some caveat during certification.
Never having seen a Duo POH, what does it say? Perhaps that's enough to
satisfy the certification requirement.

Frank Whiteley

"Chris Rollings" > wrote in message
...
> Nimbus 3 and 4 and Duo Discus brakes do not meet the
> 'speed limiting in a 45 degree dive' requirement, but
> do achieve that in a 30 degree dive. That's why they
> are non-aerobatic.
>
> At 15:18 31 March 2004, W.J. \bill\ Dean \u.K.\. wrote:
> >NO. This is thoroughly misleading.
> >
> >HISTORICAL.
> >
> >When the first gliders with good (for the day) performance
> >were built,
> >it was found that the good performance made them difficult
> >to land.
> >
> >So they were fitted with spoilers as a landing aid.
> >
> >Then pilots started to cloud fly, and some lost control
> >in cloud
> >and overspeeded and overstressed their gliders, which
> >broke up.
> >
> >This was countered by developing and fitting speed-limiting
> >airbrakes
> >(DFS, e.g. Weihe and Slingsby Sky, and Schempp-Hirth).
> > These were intended
> >to be speed limiting in a true vertical dive.
> >
> >In the U.K. it was a requirement that the glider was
> >test flown to prove
> >that at max. all up weight in a vertical dive Vne was
> >not exceeded,
> >I understand that the Slingsby Skylark series all passed
> >this test.
> >
> >Note that max. manoeuvring and rough air speeds WOULD
> >be exceeded.
> >
> >Later, it was found that with higher wing loadings,
> >thinner wing sections
> >and higher aspect ratios it became practically impossible
> >to fit true speed
> >limiting brakes (in the sense that Vne would not be
> >exceeded in a true
> >vertical dive at max. a.u.w.). The first U.K. built
> >gliders for which this
> >applied were, I believe, some at least of the Slingsby
> >Dart series.
> >
> >Also, if the rules were relaxed life would become a
> >lot easier for the
> >designer, because it would save weight and cost.
> >So the rules were
> >relaxed, and 'Speed limiting' came to mean 'In a dive
> >at X degrees', usually
> >I understand of 45 degrees.
> >
> >TODAY
> >
> >Most gliders today, including I believe all those built
> >in Europe, are
> >designed to JAR 22.
> >
> >See:
> >Joint Aviation Authorities, Europe. http://www.jaa.nl/
> >,
> >JARs - Section 1 - JAR-22 http://www.jaa.nl/section1/jars/445499.
> >>pdf .
> >
> >The relevant clause is:
> >
> >'JAR 22.73 Descent, high speed
> >
> >'It must be shown that the sailplane with the airbrakes
> >extended, will not
> >exceed VNE in a dive at an angle to the horizon of:
> >
> >'(a) 45° when the sailplane is approved for cloud flying
> >and/or aerobatics
> >when certificated in the Aerobatic or Utility Category;
> >
> >'(b) 30° in other cases.
> >
> >'[Ch. 5, 28.10.95]'
> >
> >Some modern gliders, including some being built today,
> >probably still have
> >true speed limiting brakes by the strict old definition
> >given above; my
> >guess is that these would all be gliders with trailing
> >edge brakes or
> >braking flaps such as the early Pik 20; but this would
> >not necessarily be
> >true for all gliders with such brakes.
> >
> >Some gliders were built with tailchutes, either in
> >an attempt to comply with
> >the old strict requirement, or because it was necessary
> >if they were to
> >comply with the relaxed rule. I have always understood
> >that the Janus was
> >fitted with a tailchute to be speed limiting in a 45
> >degree dive at max.
> >a.u.w. with full water ballast.
> >
> >At what dive angle would a Duo-Discus with full brakes
> >go through Vne?
> >I would be astonished if this is more than 45 degrees,
> >it may very well be
> >30 degrees.
> >
> >So if in a spin recovery, or for any other reason,
> >you are diving at a very
> >steep angle your air-brakes are unlikely to save you
> >from exceeding Vne.
> >I am sure they won't in the Nimbus 3/4 series; it was
> >not a requirement for
> >certification.
> >
> >W.J. (Bill) Dean (U.K.).
> >Remove 'ic' to reply.
> >
> >>
> >> 'Arnold Pieper' wrote in message
> >> . com...
> >>
> >> John,
> >>
> >> The airbrakes were designed not only to be used for
> >>approach and landing,
> >> but also to avoid reaching VNE.
> >>
> >> Look at your glider's POH and check what is the maximum
> >>speed to deploy
> >> the airbrakes, and what becomes the VNE with them
> >>deployed.
> >>
> >> In most modern design gliders, the airbrakes can be
> >>deployed up to VNE,
> >> and they will prevent the glider from reaching VNE
> >>when fully opened.
> >>
> >> The airbrakes are designed for this purpose.
> >>
> >> Once the airbrakes are opened and will prevent you
> >>from going over VNE,
> >> there's no need to pull at anything even close to
> >>the design limit G.
> >>
> >> Spin training therefore, is the best way to ease this
> >>fear and learn how
> >> to pull without overstressing the airframe.
> >>
> >> AP
> >>
> >> >
> >> > 'John Galloway' wrote in message
> >> > ...
> >> >
> >> > Through the contributions to the avoiding VNE thread
> >> > runs the theme of the difficulty of avoiding overspeeding
> >> > and/or overstressing some modern designs in accidental
> >> > spin recovery. This is made more difficult than
> >>>in
> >> > older composite gliders because they had a little
> >>>more
> >> > drag and a little more (fortuitous) margin in the
> >>>g
> >> > limits.
> >> >
> >> > Is it not blindingly obvious that there is a need
> >>>for
> >> > an emergency drag device that does not reduce the
> >>>G
> >> > limits of gliders? Clearly if we all handled the
> >>>recovery
> >> > from inadvertent spins etc perfectly all would be
> >>>well
> >> > but equally clearly that does not always happen and
> >> > it is a shame to lose pilots in this situation.
> >> >
> >> > As the Phoebus pilot pointed out a tail chute is
> >>>ideal
> >> > for this - providing that it can be made to actuate
> >> > and jettison reliably. (I found the design used
> >>>on
> >> > the Kestrel particularly good and I never once had
> >> > a failure for landing use.) On the other hand they
> >> > are expensive and inconvenient to replace and there
> >> > are several ways that they can fail.
> >> >
> >> > So can anyone think of a better idea than a chute?
> >> > The best I can come up with is some sort of flush
> >> > fitted rectangular-with the-long-edge-horizontal
> >>>rear
> >> > hinged airbrakes (like old fashioned automobile suicide
> >> > doors) located on the fuselage sides somewhere in
> >>>the
> >> > region below or below/behind the wings. If they
> >>>opened
> >> > to about 45 degrees with a spring actuator (and limited
> >> > by sliding metal stays that hinge/attach to the front
> >> > of the panel and whose inner ends slid along in runners)
> >> > then they would provide a lot of drag without any
> >>>deep
> >> > internal mechanism (such as wing airbrakes have).
> >> > Once they have done their job the rear end of the
> >>>brakes
> >> > could be released by a spring loaded mechanism similar
> >> > to the front end so that the brakes would then instantly
> >> > spring to as position set out from and parallel to
> >> > the fuselage so that there would be very little drag
> >> > - only that provided by the stays at both ends and
> >> > the brake panels edge on to the wind. That configuration
> >> > would be good enough to fly home with. It would
> >>>only
> >> > be possible to reset these brakes on the ground and
> >> > they would not replace conventional wing airbrakes
> >> > for approach control - although they could have a
> >>>secondary
> >> > use for emergency approach control.
> >> >
> >> > I am envisaging something the could be included in
> >> > new designs although there does not seem to be any
> >> > obvious reason why such a device could not be retrofitted
> >> > as a fairly major modification. The contours of
> >>>the
> >> > brake panels would be specific to the individual
> >>>fuselage
> >> > type but the mechanism could be generic. The assembly
> >> > would be fairly shallow and complete within itself
> >> > apart from e.g. a cable release attachment.
> >> >
> >> > I am not advocating a technical solution to this
> >>>problem
> >> > in place of spin recovery practice but I do think
> >>>that
> >> > there must be something that the combined intellects
> >> > of the gliding community can come up with other than
> >> > observing that if we get into that particular overspeeding/steep
> >>>>
> >> > attitude condition we are stuffed.
> >> >
> >> > Anyone got any simpler or better ideas? I am definitely
> >> > not an engineer.
> >> >
> >> > John Galloway
> >> >
> >>
> >
> >
> >
> >
>
>
>

[Stefan]

F.L. Whiteley wrote:

> The Type Certificate is Glider Utility Category for the Duo Discus, which
> would seem to be inappropriate given the 45degree requirement of
> JAR22.73(a),

You need to read carefully:

a) 45° when the sailplane is
*approved for cloud flying and/or aerobatics*
when certificated in the Aerobatic or Utility Category

Stefan

[F.L. Whiteley]

"Stefan" > wrote in message
...
> F.L. Whiteley wrote:
>
> > The Type Certificate is Glider Utility Category for the Duo Discus,
which
> > would seem to be inappropriate given the 45degree requirement of
> > JAR22.73(a),
>
> You need to read carefully:
>
> a) 45° when the sailplane is
> *approved for cloud flying and/or aerobatics*
> when certificated in the Aerobatic or Utility Category
>
> Stefan
>
Ah yes, good point.

Frank

[Arnie]

Denis, I hope you're just trying to make fun of the limited views some
people express here.

If you refer to the need to transfer fuel to stay in balance, the Concorde
was neither the first, nor the last airplane with that need. Fuel management
is an issue with most large airplanes, weather of not they are Delta wings
or even Supersonic.

Boing was working on a similar design (although a few years behind) at the
time the Concorde was launched, and it too would have the exact same
challenge to stay in balance, as a large delta-wing supersonic aircraft.

Or is it just that most people could never overcome the fact that the
europeans beat everyone else into the SST commercial world, and 40 years
later nobody could repeat that ?




Denis" > wrote in message
...
> Paul Repacholi wrote:
>
> > Concorde, when it was acelaring through transonic speeds had to do a
> > large fuel xfer to the aft tanks to conpensate for the strong nose
> > down trim shift.
> >
> > It was rumoured to be certified :)
>
> Surprisingly... but I'm confident that, had the soaring price of oil in
> the 70's not succeeded in killing commercially this beautiful bird, the
> FAA would not have been so kind to let it fly over the USA with such a
> dangerous feature ;-)
>
> --
> Denis
>
> R. Parce que ça rompt le cours normal de la conversation !!!
> Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?

[BllFs6]

>Or is it just that most people could never overcome the fact that the
>europeans beat everyone else into the SST commercial world, and 40 years
>later nobody could repeat that ?
>

It more like nobody is stupid enough to do it...

They predicted they would sell several hundred of em....they built about 12 and
sold none....

Yep, anothe Euro victory......

With victories like that who needs failures?

blll

[Shawn Curry]

BllFs6 wrote:
>>Or is it just that most people could never overcome the fact that the
>>europeans beat everyone else into the SST commercial world, and 40 years
>>later nobody could repeat that ?
>>
>
>
> It more like nobody is stupid enough to do it...
>
> They predicted they would sell several hundred of em....they built about 12 and
> sold none....
>
> Yep, anothe Euro victory......
>
> With victories like that who needs failures?

The Soviets?

[F.L. Whiteley]

Boeing's design was a moveable wing, akin to the F-111 and F-14. This would
have reduced the need to move fuel, at least as much, as it would shift
along with the wing. One thing about the old Boeing, they never bid or
offered an airframe that they didn't have the technology to build in hand.

Frank Whiteley

"Arnie" > wrote in message
. com...
> Denis, I hope you're just trying to make fun of the limited views some
> people express here.
>
> If you refer to the need to transfer fuel to stay in balance, the Concorde
> was neither the first, nor the last airplane with that need. Fuel
management
> is an issue with most large airplanes, weather of not they are Delta wings
> or even Supersonic.
>
> Boing was working on a similar design (although a few years behind) at the
> time the Concorde was launched, and it too would have the exact same
> challenge to stay in balance, as a large delta-wing supersonic aircraft.
>
> Or is it just that most people could never overcome the fact that the
> europeans beat everyone else into the SST commercial world, and 40 years
> later nobody could repeat that ?
>
>
>
>
> Denis" > wrote in message
> ...
> > Paul Repacholi wrote:
> >
> > > Concorde, when it was acelaring through transonic speeds had to do a
> > > large fuel xfer to the aft tanks to conpensate for the strong nose
> > > down trim shift.
> > >
> > > It was rumoured to be certified :)
> >
> > Surprisingly... but I'm confident that, had the soaring price of oil in
> > the 70's not succeeded in killing commercially this beautiful bird, the
> > FAA would not have been so kind to let it fly over the USA with such a
> > dangerous feature ;-)
> >
> > --
> > Denis
> >
> > R. Parce que ça rompt le cours normal de la conversation !!!
> > Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?
>
>

[Arnie]

Moveable wings ?
No it wasn't. Not the model shown on the old magazines I have.

It was a nice, beautiful sexy delta not unlike it's competitors.

Actually, look at what I just found on the web:
http://www.boeing.com/history/boeing/sst.html



"F.L. Whiteley" > wrote in message
...
> Boeing's design was a moveable wing, akin to the F-111 and F-14. This
would
> have reduced the need to move fuel, at least as much, as it would shift
> along with the wing. One thing about the old Boeing, they never bid or
> offered an airframe that they didn't have the technology to build in hand.
>
> Frank Whiteley
>
> "Arnie" > wrote in message
> . com...
> > Denis, I hope you're just trying to make fun of the limited views some
> > people express here.
> >
> > If you refer to the need to transfer fuel to stay in balance, the
Concorde
> > was neither the first, nor the last airplane with that need. Fuel
> management
> > is an issue with most large airplanes, weather of not they are Delta
wings
> > or even Supersonic.
> >
> > Boing was working on a similar design (although a few years behind) at
the
> > time the Concorde was launched, and it too would have the exact same
> > challenge to stay in balance, as a large delta-wing supersonic aircraft.
> >
> > Or is it just that most people could never overcome the fact that the
> > europeans beat everyone else into the SST commercial world, and 40 years
> > later nobody could repeat that ?
> >
> >
> >
> >
> > Denis" > wrote in message
> > ...
> > > Paul Repacholi wrote:
> > >
> > > > Concorde, when it was acelaring through transonic speeds had to do a
> > > > large fuel xfer to the aft tanks to conpensate for the strong nose
> > > > down trim shift.
> > > >
> > > > It was rumoured to be certified :)
> > >
> > > Surprisingly... but I'm confident that, had the soaring price of oil
in
> > > the 70's not succeeded in killing commercially this beautiful bird,
the
> > > FAA would not have been so kind to let it fly over the USA with such a
> > > dangerous feature ;-)
> > >
> > > --
> > > Denis
> > >
> > > R. Parce que ça rompt le cours normal de la conversation !!!
> > > Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?
> >
> >
>
>

[BllFs6]

>The Soviets?
>

Thats more funny than you think...

Because if I recall correctly....they outright stole design info on the
Concorde....and the French/Brits let them do it and put a few "flaws" in there
to boot...

After a few test flights, the Russian "me too SST" broke up in flight...

Thats IIRC and am not confusing this with something else...

Not to say the Russians cant be damn good engineers.....its just that this was
not one of their finer moments....

take care

Blll

[F.L. Whiteley]

Okay, that's the official history and finally contracted design, but the
much favored design was based on swing wing technology developed during the
TFX (F-111) competition. They went for fixed wing because they felt the
swing wing was so conceptually different that they wouldn't win the
contract, politicians being what they are (Jackson and Magnuson, despite
Senate status, had few electoral votes backing them up), and Boeing had a
long dry spell of winning government airplane contracts. It was a purely
pragmatic design. If you look at Boeing history, the company did not win a
federal airplane contract from the KC-135 (and it's variants, EC-135,
RC-135, E-6, C-135) until the E-4 (and that was an anomaly as there was no
real alternative plus only four were built for AF1 and NEACP). Although you
will find no attribution, this resulted from Boeing putting the government
(USAF) over a barrel in the production of the KC-135 after winning the
tanker contract, requiring that 10 707's be rolled off the line for every 15
KC-135's. That's NOT what Lemay and the USAF wanted, but Boeing won the bid
based on parallel production of the military and commercial airframes and
would go broke otherwise. The government unhappily capitulated on this, but
it stuck for a long time and Boeing started a string of bid losses. After
the C5, the company essentially focused on commercial airframe development
and gave up on chasing most government bids for a long time (note this is
the aircraft wing, not missiles). Boeing only really got back into military
aircraft by buying or partnering with established military production lines.
I can't attribute this either, but have heard it said that as much as 85% of
the B-2 was built under Boeing sub-contracts. True? I don't know, but it
might make an interesting 'follow the money' research project for some
graduate student.

The congressional hearings on McNamera's baby make interesting reading
despite all of the blacked out classified areas. It's was a four-volume set
IIRC. However, the Boeing TFX design was much superior in
design/performance to the General Dynamics implementation (not to say that
the GD result wasn't a neat airframe) and likely would have resulted in the
Navy staying in the contract. Remember Mac? He's the guy that's just
apologized for Vietnam. Anyway, after those Congressional hearings, the
feds go back and give Lockheed the nod for the C5, which, in the opinion of
many, they couldn't build at the time and the cost overruns that resulted
from developing the technology cost taxpayers several boatloads of money.

I grew up going to school with classmates with last names like Wilson,
Boullion, Stamper, and one of my best friend's father was a lead Boeing wing
engineer (from 50's until 80's). (I leave his name out as it is very unique
and googling only finds my friend, his wife, and children. His father's
work was pre-Internet, but he was published in AWST and elsewhere from time
to time). We had long, engaging discussions about this very topic and also
the C5 and the eventual cracking wing roots of the C5A (another lost Boeing
contract). He was very candide about politicians and aircraft and cost
overruns and why they happened (C5 especially, as it was timely).
Personally, he was fiscally conservative. OBTW, he had some soaring
experience in California in the early 1950's, just to keep this on track.
He was a fighter pilot instructor during WWII.

There's the 'official' Boeing history, but there are many things that
happened between Boeing and the federal government (and politicians) that
you won't find attributed to anyone. In addition to anecdotal stories, I
was part of a 100 student senior level course at the University of
Washington that studied the Boeing company in detail in 1970.

But that was the old Boeing. I hardly recognize the current corporation.

Frank Whiteley

PS: Never worked there. My mother did for six months and didn't like it
much. However, after WWII when the other aviation manufacturers were laying
off, Boeing was hiring the best engineers it could find. These were men
with talent and vision of how aviation would change the world. Most are now
gone, but what an era.

"Arnie" > wrote in message
. com...
> Moveable wings ?
> No it wasn't. Not the model shown on the old magazines I have.
>
> It was a nice, beautiful sexy delta not unlike it's competitors.
>
> Actually, look at what I just found on the web:
> http://www.boeing.com/history/boeing/sst.html
>
>
>
> "F.L. Whiteley" > wrote in message
> ...
> > Boeing's design was a moveable wing, akin to the F-111 and F-14. This
> would
> > have reduced the need to move fuel, at least as much, as it would shift
> > along with the wing. One thing about the old Boeing, they never bid or
> > offered an airframe that they didn't have the technology to build in
hand.
> >
> > Frank Whiteley
> >
> > "Arnie" > wrote in message
> > . com...
> > > Denis, I hope you're just trying to make fun of the limited views some
> > > people express here.
> > >
> > > If you refer to the need to transfer fuel to stay in balance, the
> Concorde
> > > was neither the first, nor the last airplane with that need. Fuel
> > management
> > > is an issue with most large airplanes, weather of not they are Delta
> wings
> > > or even Supersonic.
> > >
> > > Boing was working on a similar design (although a few years behind) at
> the
> > > time the Concorde was launched, and it too would have the exact same
> > > challenge to stay in balance, as a large delta-wing supersonic
aircraft.
> > >
> > > Or is it just that most people could never overcome the fact that the
> > > europeans beat everyone else into the SST commercial world, and 40
years
> > > later nobody could repeat that ?
> > >
> > >
> > >
> > >
> > > Denis" > wrote in message
> > > ...
> > > > Paul Repacholi wrote:
> > > >
> > > > > Concorde, when it was acelaring through transonic speeds had to do
a
> > > > > large fuel xfer to the aft tanks to conpensate for the strong nose
> > > > > down trim shift.
> > > > >
> > > > > It was rumoured to be certified :)
> > > >
> > > > Surprisingly... but I'm confident that, had the soaring price of oil
> in
> > > > the 70's not succeeded in killing commercially this beautiful bird,
> the
> > > > FAA would not have been so kind to let it fly over the USA with such
a
> > > > dangerous feature ;-)
> > > >
> > > > --
> > > > Denis
> > > >
> > > > R. Parce que ça rompt le cours normal de la conversation !!!
> > > > Q. Pourquoi ne faut-il pas répondre au-dessus de la question ?
> > >
> > >
> >
> >
>
>

[Shawn Curry]

BllFs6 wrote:

>>The Soviets?
>>
>
>
> Thats more funny than you think...

....not than me...
>
> Because if I recall correctly....they outright stole design info on the
> Concorde....and the French/Brits let them do it and put a few "flaws" in there
> to boot...

I knew that :-)
>
> After a few test flights, the Russian "me too SST" broke up in flight...

Apparently several Tu-144s crashed. Of course the most spectacular was
at the Paris Air show some time in the early 70s IIRC. The story is
that the French were flying a Mirage up in the clouds to get info on the
Tu-144 during a demonstration flight. The airliner pilot didn't know
about it, spotted him, and in the maneuvering to avoid stalled his
engines. In the ensuing dive to restart he was running out of altitude,
pulled up, and ripped the wings off. NOVA did a show on it a few years ago.

Shawn

[iPilot]

Afaik, this is the pretty wide-spread misconcept about the development of
TU-144 / Concorde. The fact that the end-result was very similar and many
concepts were the same doesn't nesessarily mean that one was copy of
another. The ways both design teams traveled (making concept-proving
aircrafts based on fighters for example) were very similar and their design
choices were so limited that it would be wonder if the aircrafts would have
been more different than they really were. One has to remember also that at
this time russians were on very top of the supersonic aircraft engineering.
Good example of that was Mig-21. They also knew the theory of tailless
aircrafts and had some experience with them. Putting those things together
results pretty much in the same concept that they eventually flew.


Regards,
Kaido



"BllFs6" > wrote in message
...
> >The Soviets?
> >
>
> Thats more funny than you think...
>
> Because if I recall correctly....they outright stole design info on the
> Concorde....and the French/Brits let them do it and put a few "flaws" in
there
> to boot...
>
> After a few test flights, the Russian "me too SST" broke up in flight...
>
> Thats IIRC and am not confusing this with something else...
>
> Not to say the Russians cant be damn good engineers.....its just that this
was
> not one of their finer moments....
>
> take care
>
> Blll

[Shawn Curry]

iPilot wrote:

> Afaik, this is the pretty wide-spread misconcept about the development of
> TU-144 / Concorde. The fact that the end-result was very similar and many
> concepts were the same doesn't nesessarily mean that one was copy of
> another. The ways both design teams traveled (making concept-proving
> aircrafts based on fighters for example) were very similar and their design
> choices were so limited that it would be wonder if the aircrafts would have
> been more different than they really were. One has to remember also that at
> this time russians were on very top of the supersonic aircraft engineering.
> Good example of that was Mig-21. They also knew the theory of tailless
> aircrafts and had some experience with them. Putting those things together
> results pretty much in the same concept that they eventually flew.

Yes, but there is this:
http://www.super70s.com/Super70s/Tech/Aviation/Aircraft/Tu-144.asp
and this
http://www.pbs.org/wgbh/nova/transcripts/2503supersonic.html
As for Soviet engineering, the Su 27 and Mig 29 are pretty cool.

Shawn.

[Shaber CJ]

>the only inflight breakups in such a situation
>I ever heard of were the ASW-22 prototype (1981), the eta and the US
>Nimbus, the first two being test flights of prototypes.

How about the DG-600 prototype?

[Andreas Maurer]

On Mon, 12 Apr 2004 00:46:39 GMT, Shawn Curry
> wrote:


>Yes, but there is this:
>http://www.super70s.com/Super70s/Tech/Aviation/Aircraft/Tu-144.asp
>and this
>http://www.pbs.org/wgbh/nova/transcripts/2503supersonic.html
>As for Soviet engineering, the Su 27 and Mig 29 are pretty cool.

Well... the aerodynamics of a delta wing are not that difficult... and
the Tupolev design team was not made of rookies, quite the contrary -
Tupolev had one of the best design bureaus of its time worldwide.
Maybe they got some inspiration of the Concorde (first drafts that
were very similar to the final concorde design, showing a slightly
smaller aircraft, were already published in 1959), but Concorde and
Tu-144 do not share many similarities. Wing design as well as engine
placement (especially on the first prototype) are not even similar -
the 144 is definitely an independent design.

And the famous Mirage story... well... LOL.

At an airshow you have 100.000 spectators, and dozens of hightech
cameras pointing at an aircraft that is trying to perform as close to
the ground (and the spectators and cameras) as possible.

If I want to see some details, I'd use a camera or take a closer look
at the aircraft in question while it's being parked at the static
display... but I'm not going to do a close formation flight in order
to take some aerial photographs (and hope that none of the 100.000
spectators, half of them equipped with high-focal length cameras, is
going to notice the 60 ft long and really loud Mirage that is
shadowing the airliner).

Maybe there was some near-miss... but I strongly doubt that it was
intentional by the Mirage pilot.




Bye
Andreas

[Andreas Maurer]

On 12 Apr 2004 03:49:32 GMT, (Shaber CJ) wrote:

>>the only inflight breakups in such a situation
>>I ever heard of were the ASW-22 prototype (1981), the eta and the US
>>Nimbus, the first two being test flights of prototypes.
>
>How about the DG-600 prototype?

Aileron flutter far over Vne because Wilhelm Dirks removed all
flutter-damping devices for this test flight.
One aileron started to flutter and a wing broke off, Wilhem Bailed out
at high altitude (about 10.000 ft iirc).
This happened ten miles from where I live.


Bye
Andreas