Jantars are back :)

[Janusz Kesik]

On the 1st December 2003, H. Miranda (Argentina) flying Jantar Standard 2
has set a new World Record over the 100km triangular course in Open and
15-metre classes. The speed was 249.09 kph.

Regards,


--
Janusz Kêsik,
(the Eastern Bloc crap pilot)

[Mark James Boyd]

In article >,
Janusz Kesik > wrote:
>On the 1st December 2003, H. Miranda (Argentina) flying Jantar Standard 2
>has set a new World Record over the 100km triangular course in Open and
>15-metre classes. The speed was 249.09 kph.
>
>Janusz Kêsik,
>(the Eastern Bloc crap pilot)


Isn't Vne for this glider 255 kph?


H. Miranda World Record technique:

1. Fill wings with water
2. Find wicked updraft
3. Point nose down a lot
4. Hope wings don't come off

:-]

5. Smile for the camera

[Nick Gilbert]

I think VNE for this glider is actually much faster than that. 154 kts.

Nick.


"Mark James Boyd" > wrote in message
news:3fd2360d$1@darkstar...
> In article >,
> Janusz Kesik > wrote:
> >On the 1st December 2003, H. Miranda (Argentina) flying Jantar Standard 2
> >has set a new World Record over the 100km triangular course in Open and
> >15-metre classes. The speed was 249.09 kph.
> >
> >Janusz Kêsik,
> >(the Eastern Bloc crap pilot)
>
>
> Isn't Vne for this glider 255 kph?
>
>
> H. Miranda World Record technique:
>
> 1. Fill wings with water
> 2. Find wicked updraft
> 3. Point nose down a lot
> 4. Hope wings don't come off
>
> :-]
>
> 5. Smile for the camera

[Marc Till]

Just remind how VNE varies with altitude !

Mark James Boyd a écrit:

Snip
> Isn't Vne for this glider 255 kph?
Snip

[Liam Finley]

"Janusz Kesik" > wrote in message >...
> On the 1st December 2003, H. Miranda (Argentina) flying Jantar Standard 2
> has set a new World Record over the 100km triangular course in Open and
> 15-metre classes. The speed was 249.09 kph.
>
> Regards,

What? In Eastern European manufactured junk? Impossible!

[Bob Kuykendall]

Woo-hoo! Let's hear it for the worlds fastest 63 statute mile glider flight!

[Libelle Driver]

It is not the distance, but the speed accomplished. I did a 100km attempt
on early spring day and finally got around at 19 mph, so his speed is really
great. I know it was crazy to attempt a speed task that early, but there
was no state record for that distance at the time so any time would be a
state record.


"Bob Kuykendall" > wrote in message
om...
> Woo-hoo! Let's hear it for the worlds fastest 63 statute mile glider
flight!

[Andy Henderson]

Bob,

I'm not sure if your comment is serious or not. Apologies if it is
serious.

The record is there to be beaten, no matter what length it is.

The fact it was done in an older design Jantar just makes it an even
better achievement.

The Jantars have proved to be very good gliders for their era, in
performance, ease of flying and strength. I flew one for many years
and found it to be be forgiving, reliable and as good as most at my
club.

Andy Henderson




(Bob Kuykendall) wrote in message >...
> Woo-hoo! Let's hear it for the worlds fastest 63 statute mile glider flight!

[Mark James Boyd]

In article >,
Marc Till > wrote:
>Just remind how VNE varies with altitude !
>
>Mark James Boyd a écrit:
>
>Snip
>> Isn't Vne for this glider 255 kph?
>Snip
>

Yep, I guess if you use the 2% per 1000 feet rule for TAS,
and you assume the Vne is a limitation based on flutter,
7000 feet is the absolute max altitude for this flight.

But I must say I don't entirely understand WHY flutter
is based on TAS. I also don't know if the IGC cares
if Vne is exceeded during a world record. It would
also be very hard to "prove" since GPS log only shows
groundspeed and never airspeed.

So part of my post was to say that I suspect he came close
to or exceeded Vne during the record attempt. This takes
some real confidence in the equipment and finesse about
its limits. Good for him, seriously. It's great to see
a new world record...

[Arnold Pieper]

Gents,

As far as the pilot is concerned, VNE is always read directly as an IAS
limit, that's why it's painted on the ASI as a radial line.
I've never seen any remarks about VNE as "VNE is XXX at Sea Level at ISA".
There is no such thing.

VNE is always good as an Indicated figure, except at altitudes and airspeeds
where compressibility comes into play, in which case MMO (Maximum Mach
Operating speed) becomes the limiting factor, usually well above our speeds.
That happens at a certain altitude, up to which the pilot uses the Indicated
VNE as a limit, then after that the MMO.


Exception :
Certain models of sailplanes have limitations in IAS with altitude for
various reasons,
(Flutter is not the only factor in determining VNE).
When a sailplane does have this limitation, it will be expressed so in their
manuals, and there will be a table of limiting IAS x Altitude.

Tha Jantar Std 2 is not one of these, so, VNE is good as an IAS as high as
it will go.

The bottom-line is that it dependent on each design, but VNE is not a TAS
figure, whoever told you so, doesn't know what he/she is talking about.

AP



"Mark James Boyd" > wrote in message
news:3fd4e4e4$1@darkstar...
> In article >,
> Marc Till > wrote:
> >Just remind how VNE varies with altitude !
> >
> >Mark James Boyd a écrit:
> >
> >Snip
> >> Isn't Vne for this glider 255 kph?
> >Snip
> >
>
> Yep, I guess if you use the 2% per 1000 feet rule for TAS,
> and you assume the Vne is a limitation based on flutter,
> 7000 feet is the absolute max altitude for this flight.
>
> But I must say I don't entirely understand WHY flutter
> is based on TAS. I also don't know if the IGC cares
> if Vne is exceeded during a world record. It would
> also be very hard to "prove" since GPS log only shows
> groundspeed and never airspeed.
>
> So part of my post was to say that I suspect he came close
> to or exceeded Vne during the record attempt. This takes
> some real confidence in the equipment and finesse about
> its limits. Good for him, seriously. It's great to see
> a new world record...
>
>

[Mark James Boyd]

Arnold Pieper > wrote:
>Certain models of sailplanes have limitations in IAS with altitude for
>various reasons,
>(Flutter is not the only factor in determining VNE).
>When a sailplane does have this limitation, it will be expressed so in their
>manuals, and there will be a table of limiting IAS x Altitude.

So what are these reasons? Can someone explain this a bit better?
At 25,000 feet with a 90 knot headwind I'd like to know if
pushing the nose down to redline is maybe a bad idea...
and I'm not so sure I'd be confident doing it just
because there are blank pages in the manual...

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

No.

The BGA have produced a book published 2002 by A & C Black, London titled
"Gliding - The British Gliding Association Manual", ISBN 0-7136-5947-5
(not to be confused with the book "Gliding" by Derek Piggott published in
about 1958 and now I think in its 6th edition).

This book covers the technical knowledge which the BGA thinks glider pilots
should have, and is required reading for BGA rated instructors. The main
author is Steve Longland, and he had input from many others.

In chapter 5 "The placard, structure and flight limitations" there is a
section starting on p.155 "The effects of changes in air density".
In this section an explanation is given as to why the Vne is related to True
Air Speed and not to Indicated Air Speed. I do not claim to fully
understand it myself, but I certainly intend always to obey.
The conclusion is:
"Avoiding flutter.
"The practical rule of thumb is that you should reduce the glider's Vne by
"1.5% for every 1,000ft above sea level. If your glider's Vne is 128kt,
"then at 20,000ft the ASI reading corresponding to TAS of 128kt is 90kt,
"and at 30,000ft it will be 70kt. ....."

If you read the earlier section in the same chapter about test flying, you
will see that the glider is not tested to Vd (Design dive speed) but only to
Vdf (Demonstration design speed) which is 95% of Vd and that the placard
speed Vne is 90% of Vd.
To quote from the book: "If the glider's Vne is 130kt, it has only ever been
6.5kt faster, once, when it was new, in ideal conditions, and flown by a
specially trained test pilot."

If anyone thinks this is wrong, could we please have a reasoned argument and
not just abuse.

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

>
> "Arnold Pieper" > wrote in message
> om...
>
> Gents,
>
> As far as the pilot is concerned, VNE is always read directly as an IAS
> limit, that's why it's painted on the ASI as a radial line.
> I've never seen any remarks about VNE as "VNE is XXX at Sea Level at ISA".
> There is no such thing.
>
> VNE is always good as an Indicated figure, except at altitudes and
> airspeeds where compressibility comes into play, in which case MMO
> (Maximum Mach Operating speed) becomes the limiting factor, usually well
> above our speeds. That happens at a certain altitude, up to which the
> pilot uses the Indicated VNE as a limit, then after that the MMO.
>
>
> Exception :
> Certain models of sailplanes have limitations in IAS with altitude for
> various reasons, (Flutter is not the only factor in determining VNE).
> When a sailplane does have this limitation, it will be expressed so in
> their manuals, and there will be a table of limiting IAS x Altitude.
>
> The Jantar Std 2 is not one of these, so, VNE is good as an IAS as high as
> it will go.
>
> The bottom-line is that it dependent on each design, but VNE is not a TAS
> figure, whoever told you so, doesn't know what he/she is talking about.
>
> AP
>

[Eric Greenwell]

Mark James Boyd wrote:

> Arnold Pieper > wrote:
>
>>Certain models of sailplanes have limitations in IAS with altitude for
>>various reasons,
>>(Flutter is not the only factor in determining VNE).
>>When a sailplane does have this limitation, it will be expressed so in their
>>manuals, and there will be a table of limiting IAS x Altitude.
>
>
> So what are these reasons? Can someone explain this a bit better?
> At 25,000 feet with a 90 knot headwind I'd like to know if
> pushing the nose down to redline is maybe a bad idea...
> and I'm not so sure I'd be confident doing it just
> because there are blank pages in the manual...

Old (guessing: "certified before the early '80s") sailplanes may not
have the limitation in the manual because of the regulations in effect
at the time. A lot has been learned since then, leading to more
stringent testing and more conservative ratings. If I were flying an
older glider, I'd go by the TAS unless I knew for a fact it had been
designed and tested at Vne (indicated) at high altitudes (meaning the
altitudes I'd be flying it at).
--
-----
Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

[Charles Yeates]

Maybe it would be prudent to keep one's parachute straps tight and an
emergency O2 bottle attached -- then pray for luck, The Gods do get
angry now and then.

W.J. (Bill) Dean (U.K.). wrote:
> No.
>
> The BGA have produced a book published 2002 by A & C Black, London titled
> "Gliding - The British Gliding Association Manual", ISBN 0-7136-5947-5
> (not to be confused with the book "Gliding" by Derek Piggott published in
> about 1958 and now I think in its 6th edition).
>
> This book covers the technical knowledge which the BGA thinks glider pilots
> should have, and is required reading for BGA rated instructors. The main
> author is Steve Longland, and he had input from many others.
>
> In chapter 5 "The placard, structure and flight limitations" there is a
> section starting on p.155 "The effects of changes in air density".
> In this section an explanation is given as to why the Vne is related to True
> Air Speed and not to Indicated Air Speed. I do not claim to fully
> understand it myself, but I certainly intend always to obey.
> The conclusion is:
> "Avoiding flutter.
> "The practical rule of thumb is that you should reduce the glider's Vne by
> "1.5% for every 1,000ft above sea level. If your glider's Vne is 128kt,
> "then at 20,000ft the ASI reading corresponding to TAS of 128kt is 90kt,
> "and at 30,000ft it will be 70kt. ....."
>
> If you read the earlier section in the same chapter about test flying, you
> will see that the glider is not tested to Vd (Design dive speed) but only to
> Vdf (Demonstration design speed) which is 95% of Vd and that the placard
> speed Vne is 90% of Vd.
> To quote from the book: "If the glider's Vne is 130kt, it has only ever been
> 6.5kt faster, once, when it was new, in ideal conditions, and flown by a
> specially trained test pilot."
>
> If anyone thinks this is wrong, could we please have a reasoned argument and
> not just abuse.
>
> W.J. (Bill) Dean (U.K.).
> Remove "ic" to reply.
>
>
>>"Arnold Pieper" > wrote in message
om...
>>
>>Gents,
>>
>>As far as the pilot is concerned, VNE is always read directly as an IAS
>>limit, that's why it's painted on the ASI as a radial line.
>>I've never seen any remarks about VNE as "VNE is XXX at Sea Level at ISA".
>>There is no such thing.
>>
>>VNE is always good as an Indicated figure, except at altitudes and
>>airspeeds where compressibility comes into play, in which case MMO
>>(Maximum Mach Operating speed) becomes the limiting factor, usually well
>>above our speeds. That happens at a certain altitude, up to which the
>>pilot uses the Indicated VNE as a limit, then after that the MMO.
>>
>>
>>Exception :
>>Certain models of sailplanes have limitations in IAS with altitude for
>>various reasons, (Flutter is not the only factor in determining VNE).
>>When a sailplane does have this limitation, it will be expressed so in
>>their manuals, and there will be a table of limiting IAS x Altitude.
>>
>>The Jantar Std 2 is not one of these, so, VNE is good as an IAS as high as
>>it will go.
>>
>>The bottom-line is that it dependent on each design, but VNE is not a TAS
>>figure, whoever told you so, doesn't know what he/she is talking about.
>>
>>AP
>>
>
>
>

[Denis Flament]

Mark James Boyd wrote:

> But I must say I don't entirely understand WHY flutter
> is based on TAS.

it's not. It is only because the IAS at which flutter happens is likely
to vary with altitude (it may be lower or higher !) that some
manufacturers and/or authorities limit the VNE at a constant TAS above
2000 or 3000 m (i.e. the altitude where tests have been conducted)


> I also don't know if the IGC cares
> if Vne is exceeded during a world record.

IGC don't care of exceeding any limit, with the exception of legal
day/night flight rules.

I think there is still a provision that the record may only be validated
if the glider lands back in one piece (that rule was set after some
altitude gains in CuNimbs where the pilot had jumped with the barogramm
after his glider broke ;-)

Only in championships you must have a valid permit-to-fly and respect
the limitations of your glider (weight, etc.)


--
Denis
Private replies: remove "moncourrielest" from my e-mail address
Pour me répondre utiliser l'adresse courriel figurant après
moncourrielest" dans mon adresse courriel...

[Denis Flament]

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

> No.

No to what ???


> The BGA have produced a book

Oh, I see... it written in a book ! So it is certainly true ;-)


--
Denis
Private replies: remove "moncourrielest" from my e-mail address
Pour me répondre utiliser l'adresse courriel figurant après
moncourrielest" dans mon adresse courriel...

[Arnold Pieper]

This seems to me to be some arbitrary way of staying conservative.
High altitude research is NOT an early 80s affair, I don't even know about
any such research during the 80s.

The Sierra Wave project was done during the 50s in the Owens Valley of Ca
with very old gliders that have been flown to 45000ft, altitudes at which,
according to this calculation, they would barely be able to fly.
However, curiously enough none of them flutter themselves to pieces.

To make a long story short :
-Look at the ASI on any turboprop or even some turbocharged aircraft, and
you will see that they fly at TAS much faster than the VNE painted on their
ASI.

Example : Twin Commander, VNE=255Kt (it's on it's ASI), Cruise TAS = 280Kt
to 300Kt.

The same holds true for all airplanes that fly up to the 20s and higher,
which aviation has been doing since WWII.


Look at the manual of some gliders, that do have the limitation on IAS with
Altitude.
You will see that the table of IAS is not correcting the VNE as a TAS value.

Nowhere in aviation VNE is considered a TAS value.


"W.J. (Bill) Dean (U.K.)." > wrote in message
...
> No.
>
> The BGA have produced a book published 2002 by A & C Black, London titled
> "Gliding - The British Gliding Association Manual", ISBN 0-7136-5947-5
> (not to be confused with the book "Gliding" by Derek Piggott published in
> about 1958 and now I think in its 6th edition).
>
> This book covers the technical knowledge which the BGA thinks glider
pilots
> should have, and is required reading for BGA rated instructors. The main
> author is Steve Longland, and he had input from many others.
>
> In chapter 5 "The placard, structure and flight limitations" there is a
> section starting on p.155 "The effects of changes in air density".
> In this section an explanation is given as to why the Vne is related to
True
> Air Speed and not to Indicated Air Speed. I do not claim to fully
> understand it myself, but I certainly intend always to obey.
> The conclusion is:
> "Avoiding flutter.
> "The practical rule of thumb is that you should reduce the glider's Vne by
> "1.5% for every 1,000ft above sea level. If your glider's Vne is 128kt,
> "then at 20,000ft the ASI reading corresponding to TAS of 128kt is 90kt,
> "and at 30,000ft it will be 70kt. ....."
>
> If you read the earlier section in the same chapter about test flying, you
> will see that the glider is not tested to Vd (Design dive speed) but only
to
> Vdf (Demonstration design speed) which is 95% of Vd and that the placard
> speed Vne is 90% of Vd.
> To quote from the book: "If the glider's Vne is 130kt, it has only ever
been
> 6.5kt faster, once, when it was new, in ideal conditions, and flown by a
> specially trained test pilot."
>
> If anyone thinks this is wrong, could we please have a reasoned argument
and
> not just abuse.
>
> W.J. (Bill) Dean (U.K.).
> Remove "ic" to reply.
>
> >
> > "Arnold Pieper" > wrote in message
> > om...
> >
> > Gents,
> >
> > As far as the pilot is concerned, VNE is always read directly as an IAS
> > limit, that's why it's painted on the ASI as a radial line.
> > I've never seen any remarks about VNE as "VNE is XXX at Sea Level at
ISA".
> > There is no such thing.
> >
> > VNE is always good as an Indicated figure, except at altitudes and
> > airspeeds where compressibility comes into play, in which case MMO
> > (Maximum Mach Operating speed) becomes the limiting factor, usually well
> > above our speeds. That happens at a certain altitude, up to which the
> > pilot uses the Indicated VNE as a limit, then after that the MMO.
> >
> >
> > Exception :
> > Certain models of sailplanes have limitations in IAS with altitude for
> > various reasons, (Flutter is not the only factor in determining VNE).
> > When a sailplane does have this limitation, it will be expressed so in
> > their manuals, and there will be a table of limiting IAS x Altitude.
> >
> > The Jantar Std 2 is not one of these, so, VNE is good as an IAS as high
as
> > it will go.
> >
> > The bottom-line is that it dependent on each design, but VNE is not a
TAS
> > figure, whoever told you so, doesn't know what he/she is talking about.
> >
> > AP
> >
>
>

[Jon Meyer]

Ok,

Firstly VNE is very much limited by TAS not IAS. If
you understand the maths behind how an ASI works then
you will know that the ASI indicates a TAS based on
an assumed air density equivalent to sea level. TAS
is the speed that affects flutter, IAS is simply a
gash estimate of TAS which is reasonable at low altitudes.
Hence the rules of thumb for safe flight at altitude.

Secondly, ground speed at altitude is much higher than
TAS due to lower air density and can be greatly affected
by very high velocity winds at altitude. This is how
high average speeds can be achieved without exceeding
TAS VNE. Try looking at your GPS groundspeed when at
high altitude, it should be much higher than your IAS
even when the wind effect is removed.

[Jon Meyer]

I suspect that the VNE of these aircraft will be calculated
based on IAS at cruising altitude, That is why TAS
is not mentioned. Sailplanes normally operate at a
low cruising altitude so VNE is calculated based on
IAS at (i think) 5000ft. That is why a factor has to
be applied for higher altitudes. (read Fundamentals
of Sailplane Design if you want to check)


At 19:54 09 December 2003, Arnold Pieper wrote:
>This seems to me to be some arbitrary way of staying
>conservative.
>High altitude research is NOT an early 80s affair,
>I don't even know about
>any such research during the 80s.
>
>The Sierra Wave project was done during the 50s in
>the Owens Valley of Ca
>with very old gliders that have been flown to 45000ft,
>altitudes at which,
>according to this calculation, they would barely be
>able to fly.
>However, curiously enough none of them flutter themselves
>to pieces.
>
>To make a long story short :
>-Look at the ASI on any turboprop or even some turbocharged
>aircraft, and
>you will see that they fly at TAS much faster than
>the VNE painted on their
>ASI.
>
>Example : Twin Commander, VNE=255Kt (it's on it's ASI),
>Cruise TAS = 280Kt
>to 300Kt.
>
>The same holds true for all airplanes that fly up to
>the 20s and higher,
>which aviation has been doing since WWII.
>
>
>Look at the manual of some gliders, that do have the
>limitation on IAS with
>Altitude.
>You will see that the table of IAS is not correcting
>the VNE as a TAS value.
>
>Nowhere in aviation VNE is considered a TAS value.
>
>
>'W.J. (Bill) Dean (U.K.).' wrote in message
...
>> No.
>>
>> The BGA have produced a book published 2002 by A &
>>C Black, London titled
>> 'Gliding - The British Gliding Association Manual',
>>ISBN 0-7136-5947-5
>> (not to be confused with the book 'Gliding' by Derek
>>Piggott published in
>> about 1958 and now I think in its 6th edition).
>>
>> This book covers the technical knowledge which the
>>BGA thinks glider
>pilots
>> should have, and is required reading for BGA rated
>>instructors. The main
>> author is Steve Longland, and he had input from many
>>others.
>>
>> In chapter 5 'The placard, structure and flight limitations'
>>there is a
>> section starting on p.155 'The effects of changes
>>in air density'.
>> In this section an explanation is given as to why
>>the Vne is related to
>True
>> Air Speed and not to Indicated Air Speed. I do not
>>claim to fully
>> understand it myself, but I certainly intend always
>>to obey.
>> The conclusion is:
>> 'Avoiding flutter.
>> 'The practical rule of thumb is that you should reduce
>>the glider's Vne by
>> '1.5% for every 1,000ft above sea level. If your
>>glider's Vne is 128kt,
>> 'then at 20,000ft the ASI reading corresponding to
>> TAS of 128kt is 90kt,
>> 'and at 30,000ft it will be 70kt. .....'
>>
>> If you read the earlier section in the same chapter
>>about test flying, you
>> will see that the glider is not tested to Vd (Design
>>dive speed) but only
>to
>> Vdf (Demonstration design speed) which is 95% of Vd
>>and that the placard
>> speed Vne is 90% of Vd.
>> To quote from the book: 'If the glider's Vne is 130kt,
>>it has only ever
>been
>> 6.5kt faster, once, when it was new, in ideal conditions,
>>and flown by a
>> specially trained test pilot.'
>>
>> If anyone thinks this is wrong, could we please have
>>a reasoned argument
>and
>> not just abuse.
>>
>> W.J. (Bill) Dean (U.K.).
>> Remove 'ic' to reply.
>>
>> >
>> > 'Arnold Pieper' wrote in message
>> > om...
>> >
>> > Gents,
>> >
>> > As far as the pilot is concerned, VNE is always read
>>>directly as an IAS
>> > limit, that's why it's painted on the ASI as a radial
>>>line.
>> > I've never seen any remarks about VNE as 'VNE is
>>>XXX at Sea Level at
>ISA'.
>> > There is no such thing.
>> >
>> > VNE is always good as an Indicated figure, except
>>>at altitudes and
>> > airspeeds where compressibility comes into play,
>>>in which case MMO
>> > (Maximum Mach Operating speed) becomes the limiting
>>>factor, usually well
>> > above our speeds. That happens at a certain altitude,
>>>up to which the
>> > pilot uses the Indicated VNE as a limit, then after
>>>that the MMO.
>> >
>> >
>> > Exception :
>> > Certain models of sailplanes have limitations in
>>>IAS with altitude for
>> > various reasons, (Flutter is not the only factor
>>>in determining VNE).
>> > When a sailplane does have this limitation, it will
>>>be expressed so in
>> > their manuals, and there will be a table of limiting
>>>IAS x Altitude.
>> >
>> > The Jantar Std 2 is not one of these, so, VNE is
>>>good as an IAS as high
>as
>> > it will go.
>> >
>> > The bottom-line is that it dependent on each design,
>>>but VNE is not a
>TAS
>> > figure, whoever told you so, doesn't know what he/she
>>>is talking about.
>> >
>> > AP
>> >
>>
>>
>
>
>

[Simon Kahn]

From DG website DG1000 flight manual:

http://www.dg-flugzeugbau.de/index-e.html
==========
Warning: At higher altitudes the true airspeed is higher
than the indicated airspeed, so VNE is reduced with
altitude according to the table below, see also section
4.5.5.

Altitude in [m] 0-3000 4000 5000 6000 7000
8000
VNE indicated km/h 270 256 243 230 217
205

Altitude in [ft] 0-10000 13000 16000 20000
23000 26000
VNE indicated kts. 146 138 131
124 117 111

-------
Simon.

> 19:54 09 December 2003, Arnold Pieper wrote:
>This seems to me to be some arbitrary way of staying
>conservative.
>Look at the manual of some gliders, that do have the
>limitation on IAS with Altitude.
>You will see that the table of IAS is not correcting
>the VNE as >a TAS value.
>
>Nowhere in aviation VNE is considered a TAS value.
>

[John Giddy]

"Jon Meyer" > wrote in
message ...
| Ok,
|
| Firstly VNE is very much limited by TAS not IAS. If
| you understand the maths behind how an ASI works then
| you will know that the ASI indicates a TAS based on
| an assumed air density equivalent to sea level. TAS
| is the speed that affects flutter, IAS is simply a
| gash estimate of TAS which is reasonable at low altitudes.
| Hence the rules of thumb for safe flight at altitude.
|
| Secondly, ground speed at altitude is much higher than
| TAS due to lower air density and can be greatly affected
| by very high velocity winds at altitude. This is how
| high average speeds can be achieved without exceeding
| TAS VNE. Try looking at your GPS groundspeed when at
| high altitude, it should be much higher than your IAS
| even when the wind effect is removed.

I am confused !
How can the ground speed exceed TAS when measured in still
air ?
TAS means TRUE Air Speed. i.e. the actual speed of the
aircraft through the particular parcel of air around the
aircraft. If this parcel of air is stationary with respect
to the ground, the ground speed of the aircraft must equal
the TAS.
Cheers, John G.

[Eric Greenwell]

Arnold Pieper wrote:

> To make a long story short :
> -Look at the ASI on any turboprop or even some turbocharged aircraft, and
> you will see that they fly at TAS much faster than the VNE painted on their
> ASI.
>
> Example : Twin Commander, VNE=255Kt (it's on it's ASI), Cruise TAS = 280Kt
> to 300Kt.
>
> The same holds true for all airplanes that fly up to the 20s and higher,
> which aviation has been doing since WWII.
>
>
> Look at the manual of some gliders, that do have the limitation on IAS with
> Altitude.
> You will see that the table of IAS is not correcting the VNE as a TAS value.
>
> Nowhere in aviation VNE is considered a TAS value.

Quoting from the manual for my Schleicher ASH 26 E:

"4.5.8 High altitude flight

Flutter tests were carried out at about 2000 m msl. As the ASI
under-reads at increasing altitude, but since flutter limits for light
aircraft are determined by the true air speed, the following limitations
apply to high altitude flights:" [table of IAS at Vne for altitudes to
13000m follows]

--
-----
Replace "SPAM" with "charter" to email me directly

Eric Greenwell
Washington State
USA

[Arnold Pieper]

Jon,

I don't like to come accross as arrogant, I'm sorry if I do, but you seem to
be confusing the issue.

IAS is what you see in your ASI.
TAS is the speed at which the aircraft is is moving trough the air (nothing
to do with groundspeed).

To obtain you TAS at any time during flight, you look at what your ASI is
indicating, then apply a correction based on altitude and oustide air
temperature. You can do that with an E-6B type computer.
If you don't have an OAT reading, you're out of luck, but the well-known 2%
per 1000ft will give you an approximation.

Groundspeed, on the other hand is the speed at which you move in relation to
the ground.
The Groundspeed is the result of your TAS plus (or minus) the wind
component.

When I say most Turboprops and Turbocharged airplanes fly at faster TAS than
their IAS VNEs,
that's exactly what I mean :
At altitudes of 20k plus, their TAS will be higher than their indicated VNE,
regardless of what the Groundspeed is.

The Twin commander will be reading Groundspeeds of 350Kt when eastbound
(tailwind) and it may read as little as 230Kt westbound.
But in both cases, with the same power setting, it will be doing 290Kt TAS,
which is more than the 255Kt VNE.

Meanwhile, their ASI will be showing 180Kt to 190Kt, depending on altitude
and powersetting, well below the VNE of 255Kt.

Same thing holds true for all these airplanes. Other examples :
TBM-700, cruises at 290Kt TAS (not groundspeed), while the VNE is 265Kt.
King Air 350, cruises at 300Kt TAS, VNE is 265Kt.





"Jon Meyer" > wrote in message
...
> Ok,
>
> Firstly VNE is very much limited by TAS not IAS. If
> you understand the maths behind how an ASI works then
> you will know that the ASI indicates a TAS based on
> an assumed air density equivalent to sea level. TAS
> is the speed that affects flutter, IAS is simply a
> gash estimate of TAS which is reasonable at low altitudes.
> Hence the rules of thumb for safe flight at altitude.
>
> Secondly, ground speed at altitude is much higher than
> TAS due to lower air density and can be greatly affected
> by very high velocity winds at altitude. This is how
> high average speeds can be achieved without exceeding
> TAS VNE. Try looking at your GPS groundspeed when at
> high altitude, it should be much higher than your IAS
> even when the wind effect is removed.
>
>
>
>

[Arnold Pieper]

Thank you Simon,

Exaclty like I said in a previous message :
The table below confirms it, It is NOT simply the VNE corrected as TAS.

Go ahead and check this table if you will :
100Kt IAS @ 26000ft is LEGAL, ALLOWED and SAFE as per the manual.
That's because table shows 111Kt IAS as being the limit at this altitude.

Now calculate your TAS for this condition (100Kt IAS @ 26000ft), with
various range of temperatures.
Here's what you will get as TAS for the various temperatures :
163Kt @ -45 Celsius (way below Standard),
167Kt @ -35 Celsius (aprox. std temperature for this altitude)
170Kt @ -25 Celsius (above Standard)

All of these TAS are higher than the original Low-altitude IAS VNE of
146Kt, painted on the ASI.
Which confirms what I said : the VNE is NOT simply to be corrected as a TAS
figure.

This limitation in IAS with Altitudes are "NEW" values for VNE, due to
flutter or whatever the reason with altitude.
But the resulting TAS at these conditions will be higher than the original
VNE.




"Simon Kahn" > wrote in message
...
> From DG website DG1000 flight manual:
>
> http://www.dg-flugzeugbau.de/index-e.html
> ==========
> Warning: At higher altitudes the true airspeed is higher
> than the indicated airspeed, so VNE is reduced with
> altitude according to the table below, see also section
> 4.5.5.
>
> Altitude in [m] 0-3000 4000 5000 6000 7000
> 8000
> VNE indicated km/h 270 256 243 230 217
> 205
>
> Altitude in [ft] 0-10000 13000 16000 20000
> 23000 26000
> VNE indicated kts. 146 138 131
> 124 117 111
>
> -------
> Simon.
>
> > 19:54 09 December 2003, Arnold Pieper wrote:
> >This seems to me to be some arbitrary way of staying
> >conservative.
> >Look at the manual of some gliders, that do have the
> >limitation on IAS with Altitude.
> >You will see that the table of IAS is not correcting
> >the VNE as >a TAS value.
> >
> >Nowhere in aviation VNE is considered a TAS value.
> >
>
>
>
>

[Eric Greenwell]

Arnold Pieper wrote:

> Thank you Simon,
>
> Exaclty like I said in a previous message :
> The table below confirms it, It is NOT simply the VNE corrected as TAS.
>
> Go ahead and check this table if you will :
> 100Kt IAS @ 26000ft is LEGAL, ALLOWED and SAFE as per the manual.
> That's because table shows 111Kt IAS as being the limit at this altitude.
>
> Now calculate your TAS for this condition (100Kt IAS @ 26000ft), with
> various range of temperatures.
> Here's what you will get as TAS for the various temperatures :
> 163Kt @ -45 Celsius (way below Standard),
> 167Kt @ -35 Celsius (aprox. std temperature for this altitude)
> 170Kt @ -25 Celsius (above Standard)
>
> All of these TAS are higher than the original Low-altitude IAS VNE of
> 146Kt, painted on the ASI.
> Which confirms what I said : the VNE is NOT simply to be corrected as a TAS
> figure.
>
> This limitation in IAS with Altitudes are "NEW" values for VNE, due to
> flutter or whatever the reason with altitude.
> But the resulting TAS at these conditions will be higher than the original
> VNE.

Perhaps you missed this post:

Quoting from the manual for my Schleicher ASH 26 E:

"4.5.8 High altitude flight

Flutter tests were carried out at about 2000 m msl. As the ASI
under-reads at increasing altitude, but since flutter limits for light
aircraft are determined by the true air speed, the following limitations
apply to high altitude flights:

[table of IAS at Vne for altitudes to 13000m follows]

If above airspeed limits given as IAS are regarded the true air speed
above 3000 m altitude will remain constant at 300 km/h = 162 knots."

So for this glider, the Vne in TAS does increase to 10,000', then
remains at a constant 162 knots TAS. They are quite explicit about the
Vne depending on TAS.

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

Eric Greenwell
Washington State
USA

[Arnold Pieper]

Eric,

Thanks, I see how explicit they are about it.
DG chose to not get into specifics, because the story is a bit more complex
than that.

The VNE of your glider is 146Kt (IAS), but above 10000' you should start
observing other IAS limits, that translate into 162Kt TAS due to flutter
considerations.

Therefore, simply using 146Kt as a TAS value is not correct, which is what
was being suggested earlier, and is what I had trouble with.

Nowhere in Aeronautic literature is VNE defined as a TAS value, it HAS to be
presented to the pilot as Indicated.

In high-performance aircraft where flutter is less of a consideration, there
is no such table for high altitude, VNE is always VNE, until MMo becomes a
factor.



"Eric Greenwell" > wrote in message
...
> Arnold Pieper wrote:
>
> > Thank you Simon,
> >
> > Exaclty like I said in a previous message :
> > The table below confirms it, It is NOT simply the VNE corrected as TAS.
> >
> > Go ahead and check this table if you will :
> > 100Kt IAS @ 26000ft is LEGAL, ALLOWED and SAFE as per the manual.
> > That's because table shows 111Kt IAS as being the limit at this
altitude.
> >
> > Now calculate your TAS for this condition (100Kt IAS @ 26000ft), with
> > various range of temperatures.
> > Here's what you will get as TAS for the various temperatures :
> > 163Kt @ -45 Celsius (way below Standard),
> > 167Kt @ -35 Celsius (aprox. std temperature for this altitude)
> > 170Kt @ -25 Celsius (above Standard)
> >
> > All of these TAS are higher than the original Low-altitude IAS VNE of
> > 146Kt, painted on the ASI.
> > Which confirms what I said : the VNE is NOT simply to be corrected as a
TAS
> > figure.
> >
> > This limitation in IAS with Altitudes are "NEW" values for VNE, due to
> > flutter or whatever the reason with altitude.
> > But the resulting TAS at these conditions will be higher than the
original
> > VNE.
>
> Perhaps you missed this post:
>
> Quoting from the manual for my Schleicher ASH 26 E:
>
> "4.5.8 High altitude flight
>
> Flutter tests were carried out at about 2000 m msl. As the ASI
> under-reads at increasing altitude, but since flutter limits for light
> aircraft are determined by the true air speed, the following limitations
> apply to high altitude flights:
>
> [table of IAS at Vne for altitudes to 13000m follows]
>
> If above airspeed limits given as IAS are regarded the true air speed
> above 3000 m altitude will remain constant at 300 km/h = 162 knots."
>
> So for this glider, the Vne in TAS does increase to 10,000', then
> remains at a constant 162 knots TAS. They are quite explicit about the
> Vne depending on TAS.
>
> --
> -----
> change "netto" to "net" to email me directly
>
> Eric Greenwell
> Washington State
> USA
>

[John Giddy]

"Arnold Pieper" > wrote in
message
om...
| Eric,
|
| Thanks, I see how explicit they are about it.
| DG chose to not get into specifics, because the story is a
bit more complex
| than that.
|
| The VNE of your glider is 146Kt (IAS), but above 10000'
you should start
| observing other IAS limits, that translate into 162Kt TAS
due to flutter
| considerations.
|
| Therefore, simply using 146Kt as a TAS value is not
correct, which is what
| was being suggested earlier, and is what I had trouble
with.
|
| Nowhere in Aeronautic literature is VNE defined as a TAS
value, it HAS to be
| presented to the pilot as Indicated.
|
| In high-performance aircraft where flutter is less of a
consideration, there
| is no such table for high altitude, VNE is always VNE,
until MMo becomes a
| factor.

I think the statement that you should use TAS as the limit
for Vne rather than IAS, comes from earlier times, when less
was known about instabilities such as flutter. I have heard
it said that something between IAS and TAS is what affects
flutter, but the percentage will change from one aircraft to
another, so it is safe to use TAS as a Vne limit. No one
said it was an exact statement, but it is known to be
*safe*.
TAS is calculated by power pilots as a matter of course for
flight planning, so the conversion is well known and easily
available on the various flight computers ("prayer wheels"
and such)
It is sometimes mandated by local Authorities that a table
based on manufacturer's data or TAS is provided.
The Gliding Federation of Australia has such a stipulation,
tied to the installation of oxygen in a glider. Part of the
installation is a placard to be fixed in the cockpit which
shows the table of Indicated Vne versus altitude, derived
either from the manufacturer's table or calculated using TAS
conversion for a standard atmosphere (pressure and
temperature with height)
Whether either table is "right" is immaterial, as long as
the table gives the pilot *safe* information.
Cheers, John G.

[Jon Meyer]

Sorry,

Misprint, The Groundspeed at altitude will be equal
to TAS and therefore much higher than the IAS (not
TAS as I earlier stated). That is why your groundspeed
will be higher than IAS.
This was simply meant in answer to the confusion of
how someone could achieve an average speed of 250+kph
at 20000ft nwithout exceeding VNE at altitude.

I am not confused about the issues concerning flutter.
Flutter is dependant on TAS. IAS is an arbitrary value
based on sea level air density. I still believe that
the reason you are confused is that the VNE of the
'high performance' aircraft you describe is specified
as IAS at cruising altitude - not at sea level. Therefore
your calculation of TAS being higher than VNE is flawed
because you have taken the wrong air density as your
datum.




At 20:12 09 December 2003, Jon Meyer wrote:
>Ok,
>
>Firstly VNE is very much limited by TAS not IAS. If
>you understand the maths behind how an ASI works then
>you will know that the ASI indicates a TAS based on
>an assumed air density equivalent to sea level. TAS
>is the speed that affects flutter, IAS is simply a
>gash estimate of TAS which is reasonable at low altitudes.
>Hence the rules of thumb for safe flight at altitude.
>
>Secondly, ground speed at altitude is much higher than
>TAS due to lower air density and can be greatly affected
>by very high velocity winds at altitude. This is how
>high average speeds can be achieved without exceeding
>TAS VNE. Try looking at your GPS groundspeed when at
>high altitude, it should be much higher than your IAS
>even when the wind effect is removed.
>
>
>
>
>

[Denis Flament]

Jon Meyer wrote:

> Secondly, ground speed at altitude is much higher than
> TAS due to lower air density
^^^^^ ^^^ ^^^^^^^

Are you joking ?


--
Denis
Private replies: remove "moncourrielest" from my e-mail address
Pour me répondre utiliser l'adresse courriel figurant après
moncourrielest" dans mon adresse courriel...

[Mark James Boyd]

Jon Meyer > wrote:
>Sorry,
>
>I am not confused about the issues concerning flutter.
>Flutter is dependant on TAS. IAS is an arbitrary value
>based on sea level air density. I still believe that
>the reason you are confused is that the VNE of the
>'high performance' aircraft you describe is specified
>as IAS at cruising altitude - not at sea level. Therefore
>your calculation of TAS being higher than VNE is flawed
>because you have taken the wrong air density as your
>datum.
>

So Vne of power planes is a figure which
describes Vne at the highest cruising altitude? So
this means that actual Vne at a lower altitude may
be faster? Hmmm...this seems to make sense for power
planes...

Unfortunately gliders don't have an altitude limited by
power. So this is much stickier. I noticed the PW-5
initially had a 15,000 foot altitude limitation (1998?)
and there were some vigorous complaints. Then
apparently the limitation was removed (don't know
exactly why). Perhaps test pilots determined the
"flutter" was caused by gaps in the elevator connection
and not actual "flutter."

But what this seems to suggest is that a manual which
does not specifically address Vne and altitude should
be viewed with skepticism. A grob 102 at 49,000 feet
pushed to Vne makes you a test pilot...

Excellent discussion! Fantastic fountain of (sometimes
varied) opinions and advice. It's also nice to
see the thoughts converging, and I can visualize
a lot of readers shuffling through arcane texts
asking "is that really true?" Thanks for your posts...

[Eric Greenwell]

Arnold Pieper wrote:

> Eric,
>
> Thanks, I see how explicit they are about it.
> DG chose to not get into specifics, because the story is a bit more complex
> than that.

Even though they are explicit about it, I'm not sure if the reason is
regulatory or physical. An aeronautics fellow told me flutter doesn't
strictly follow TAS, but is somewhat higher, but testing at high
altitudes is needed to confirm exactly where it is.

> The VNE of your glider is 146Kt (IAS), but above 10000' you should start
> observing other IAS limits, that translate into 162Kt TAS due to flutter
> considerations.

Again, I'm not sure where the 10,000' comes from: possibly below that,
Vne is restricted to IAS for reasons other than flutter, but above that,
flutter becomes the critical factor.

> Therefore, simply using 146Kt as a TAS value is not correct, which is what
> was being suggested earlier, and is what I had trouble with.
>
> Nowhere in Aeronautic literature is VNE defined as a TAS value, it HAS to be
> presented to the pilot as Indicated.

My glider manual does require a placard giving that information.
>
> In high-performance aircraft where flutter is less of a consideration, there
> is no such table for high altitude, VNE is always VNE, until MMo becomes a
> factor.

It would be interesting to know why there is a difference, but I suspect
it might the regulatory requirements for different categories.

--
-----
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Eric Greenwell
Washington State
USA

[F.L. Whiteley]

"Mark James Boyd" > wrote in message
news:3fd75f4f$1@darkstar...
> Jon Meyer > wrote:
> >Sorry,
> >
> >I am not confused about the issues concerning flutter.
> >Flutter is dependant on TAS. IAS is an arbitrary value
> >based on sea level air density. I still believe that
> >the reason you are confused is that the VNE of the
> >'high performance' aircraft you describe is specified
> >as IAS at cruising altitude - not at sea level. Therefore
> >your calculation of TAS being higher than VNE is flawed
> >because you have taken the wrong air density as your
> >datum.
> >
>
> So Vne of power planes is a figure which
> describes Vne at the highest cruising altitude? So
> this means that actual Vne at a lower altitude may
> be faster? Hmmm...this seems to make sense for power
> planes...
>
> Unfortunately gliders don't have an altitude limited by
> power. So this is much stickier. I noticed the PW-5
> initially had a 15,000 foot altitude limitation (1998?)
> and there were some vigorous complaints. Then
> apparently the limitation was removed (don't know
> exactly why). Perhaps test pilots determined the
> "flutter" was caused by gaps in the elevator connection
> and not actual "flutter."
>
> But what this seems to suggest is that a manual which
> does not specifically address Vne and altitude should
> be viewed with skepticism. A grob 102 at 49,000 feet
> pushed to Vne makes you a test pilot...
>
> Excellent discussion! Fantastic fountain of (sometimes
> varied) opinions and advice. It's also nice to
> see the thoughts converging, and I can visualize
> a lot of readers shuffling through arcane texts
> asking "is that really true?" Thanks for your posts...
From my 2000 post on this topic.
<quote>
There was an interesting article in Technical Soaring a few years ago about
much of this. In gliders there is also an elastic flutter mode WRT the
center of pressure and location of the wing spar in modern composites and
the resultant bad twisting things when the threshold was reached. This is
separate from control and PIO induced flutter modes.

IIRC, this results from design/weight considerations, airbrake and ballast
tank placements, and optimization of designs [spar placement where
applicable] for operating <6000m most of
the time [like 99%]. The proposal of the article was for consideration of a
high
altitude VNe (with an adequate margin of safety) somewhat higher that TAS
VNe. I believe the formula was (VNe (TAS) + VNe (IAS)) / 2. I don't know
if this proposal has since been discredited or tested. The authors
postulated the actual safe zone extended up to something like 0.8 *
VNe(IAS).

AFAIK, no testing of gliders above 6000m is done by or required of
manufacturers. Thus, if you are heading really high, you're a test pilot.

I keep waiting for Technical Soaring archives to appear on CD-ROM. BTW
Larry, if you're lurking, what's the current status of this (IMVHO long
overdue) project?

[ADDED WRT to the above para: OSTIV is supposed to be working CD-ROM
distribution of old articles
according to my last contact about a year ago.]

Frank Whiteley
Colorado
</unquote>

[Arnold Pieper]

Jon,

My "calculation" of TAS being higher then VNE is flawed ???

It's simple. Real life scenario :
ASI has the VNE (painted on) at 255 kt.
Cruise IAS at 25000ft is 185Kt (well below the VNE).
OAT shows -25 celsius at this altitude.

The TAS calculation using any E6B computer shows TAS at this condition to be
272Kt.
I'll say again, TAS at this altitude is therefore 272kt.

If you were to reach VNE at this altitude, your TAS would be 364kt.
So you are IN FACT below VNE. Of course. That's the whole point.

The VNE painted on the ASI says 255Kt, but that is INDICATED, and someone
thought that was to be taken as TAS, which is wrong.




"Mark James Boyd" > wrote in message
news:3fd75f4f$1@darkstar...
> Jon Meyer > wrote:
> >Sorry,
> >
> >I am not confused about the issues concerning flutter.
> >Flutter is dependant on TAS. IAS is an arbitrary value
> >based on sea level air density. I still believe that
> >the reason you are confused is that the VNE of the
> >'high performance' aircraft you describe is specified
> >as IAS at cruising altitude - not at sea level. Therefore
> >your calculation of TAS being higher than VNE is flawed
> >because you have taken the wrong air density as your
> >datum.
> >
>
> So Vne of power planes is a figure which
> describes Vne at the highest cruising altitude? So
> this means that actual Vne at a lower altitude may
> be faster? Hmmm...this seems to make sense for power
> planes...
>

[Mark James Boyd]

>I think there is still a provision that the record may only be validated
>if the glider lands back in one piece (that rule was set after some
>altitude gains in CuNimbs where the pilot had jumped with the barogramm
>after his glider broke ;-)
>
>Denis

C'mon, is that really true? How did he prove he was
still in the "aerodyne" when the barograph got its highest
altitude? Maybe he was just a big piece of hail.
My gosh, maybe he used the baro to tell his altitude
to make sure he didn't pull his chute too early...LOL

[Jon Meyer]

I think you misunderstood what I meant.
The IAS VNE at cruising altitude of 20000ft is 272kts
(assuming as I said before that IAS VNE is at cruising
altitude) . This equates to a TAS of 364kts. Which
means that VNE is 364kts TAS.
So in this aircraft at sea-level you could technically
go to 364kts IAS and still be below VNE.

again I'll re-iterate that VNE is influenced by TAS
(and Mach Number) NOT by IAS, which is merely an approximation
of TAS valid at sea level.

Your calculations were fine, it was just the assumption
that VNE would be based on sea level conditions rather
than cruise conditions that i think was wrong. I could
be wrong too, but it just seems logical that for an
aircraft that spends most of its time at 20000ft the
VNE should be based on IAS at this altitude to make
things simpler for the pilot.

Regards,
Jon.


p.s. Dont get any ideas about going above IAS VNE at
sea level in your glider - its VNE is normally based
on IAS at 5000ft leaving very little margin.

[Eric Greenwell]

Jon Meyer wrote:
> I think you misunderstood what I meant.
> The IAS VNE at cruising altitude of 20000ft is 272kts
> (assuming as I said before that IAS VNE is at cruising
> altitude) . This equates to a TAS of 364kts. Which
> means that VNE is 364kts TAS.
> So in this aircraft at sea-level you could technically
> go to 364kts IAS and still be below VNE.

Did you really mean "Vne", or just flutter related aspects of Vne?
Obviously, the potential aerodynamic loads will be about 80% greater at
364kts TAS at sea level.

> again I'll re-iterate that VNE is influenced by TAS
> (and Mach Number) NOT by IAS, which is merely an approximation
> of TAS valid at sea level.

But isn't aerodynamic pressure an important factor (i.e, "influence") in
flutter? And that is what IAS measures?
--
-----
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Eric Greenwell
Washington State
USA

[Arnold Pieper]

Jon,

The only way to reach VNE is by diving, not by fling staight and level in
cruise.
And you can dive from 1000ft or from very high altitudes.
All the while the VNE is that radial line painted on you ASI, which reads
Indicated Airspeed and has to be respected as you see it (not in your mind
or in some calculator).
The exception for limits related to flutter in Gliders are done in the form
of a table so that you don't have to do mental math.

VNE is usually set at some % below whatever fenomenon determined it.
It might be different things for diffent aircraft, sometimes as simple as a
windshield that will not resist above a certain pressure, or even the
position of the glider (VNE for inverted flight is different from upright).
So, if you dive and your ASI pointer goes above that radial line that marks
VNE,
bad things will happen, regardless of altitude.

The ASI "underreads" at any altitude above Sea Level @ ISA conditions.
The aircraft surfaces "feel" the air the same way the ASI does, which means
most
aerodynamic reactions respond to the same Indicated Air Speed, regardless of
altitude.
That's why your Stalling Speed is at the bottom of the green arc, and it is
the same at 1000ft or at 10000ft.
Same holds true for gear extension/operation speed limits, flap speed
limits,
storm window speed limits and so forth.

The stuff that is REQUIRED by regulations to be painted on the ASI, are all
reactions that remain constant with Indicated Airspeed, that's why they are
painted on it.

The events that will occur at different IAS with different altitudes are NOT
painted on the ASI exactly because they vary.
They are related to Power (HP, SHP or LBS of Thrust), which always reduces
with altitude.
Examples are Vx and Vy for power airplanes, Vmc (for twins) and things like
that.

Not so with VNE witch is painted-on.
The reactions to flutter on gliders will however, require "new" VNEs at
higher altitudes, if you review all recent postings on these "tables of VNE
with altitude" it will become clear.

AP


"Jon Meyer" > wrote in message
...
> I think you misunderstood what I meant.
> The IAS VNE at cruising altitude of 20000ft is 272kts
> (assuming as I said before that IAS VNE is at cruising
> altitude) . This equates to a TAS of 364kts. Which
> means that VNE is 364kts TAS.
(.....................)

[Mark Parker]

At 00:36 12 December 2003, Arnold Pieper wrote:
>Jon,
>
>The only way to reach VNE is by diving, not by fling
>staight and level in
>cruise.

Hope you dont mean that literally Arnold! I had a go
in a microlight once that had a cruise speed only 10kts
below its VNE!!- very easy to exceed vne in straight
& level. Plus in a glider if the wave/ridge is strong
enough you can get to VNE can't you?

Apart from that I think you explained the whole altitude/
density/ flutter /vne faff quite well.

Some people around here have incredibly complicated
ways of explaining things! With that in mind, for
the next debate can I suggest an explanation of :

Transition level, transition altitude, transition layer
and altimeter settings!? QFE QNH SPS....

AAARHGH NO! on second thoughts spare us!! :-) :-)



>And you can dive from 1000ft or from very high altitudes.
>All the while the VNE is that radial line painted on
>you ASI, which reads
>Indicated Airspeed and has to be respected as you see
>it (not in your mind
>or in some calculator).
>The exception for limits related to flutter in Gliders
>are done in the form
>of a table so that you don't have to do mental math.
>
>VNE is usually set at some % below whatever fenomenon
>determined it.
>It might be different things for diffent aircraft,
>sometimes as simple as a
>windshield that will not resist above a certain pressure,
>or even the
>position of the glider (VNE for inverted flight is
>different from upright).
>So, if you dive and your ASI pointer goes above that
>radial line that marks
>VNE,
>bad things will happen, regardless of altitude.
>
>The ASI 'underreads' at any altitude above Sea Level
>@ ISA conditions.
>The aircraft surfaces 'feel' the air the same way the
>ASI does, which means
>most
>aerodynamic reactions respond to the same Indicated
>Air Speed, regardless of
>altitude.
>That's why your Stalling Speed is at the bottom of
>the green arc, and it is
>the same at 1000ft or at 10000ft.
>Same holds true for gear extension/operation speed
>limits, flap speed
>limits,
>storm window speed limits and so forth.
>
>The stuff that is REQUIRED by regulations to be painted
>on the ASI, are all
>reactions that remain constant with Indicated Airspeed,
>that's why they are
>painted on it.
>
>The events that will occur at different IAS with different
>altitudes are NOT
>painted on the ASI exactly because they vary.
>They are related to Power (HP, SHP or LBS of Thrust),
>which always reduces
>with altitude.
>Examples are Vx and Vy for power airplanes, Vmc (for
>twins) and things like
>that.
>
>Not so with VNE witch is painted-on.
>The reactions to flutter on gliders will however, require
>'new' VNEs at
>higher altitudes, if you review all recent postings
>on these 'tables of VNE
>with altitude' it will become clear.
>
>AP
>
>
>'Jon Meyer' wrote in message
...
>> I think you misunderstood what I meant.
>> The IAS VNE at cruising altitude of 20000ft is 272kts
>> (assuming as I said before that IAS VNE is at cruising
>> altitude) . This equates to a TAS of 364kts. Which
>> means that VNE is 364kts TAS.
>(.....................)
>
>
>

[Bruce Hoult]

In article >,
Mark Parker > wrote:

> Plus in a glider if the wave/ridge is strong
> enough you can get to VNE can't you?

Yery easily. Most gliders have descent rates less than 1000 feet per
minute at Vne, and the better ones are more like 500 fpm. That's 5 - 10
knots down, which means that a 10 - 20 knot wind hitting a reasonably
steep hill (30 degrees, sin = 0.5) is enough to keep a glider at Vne in
level flight. And if the hill is 45 or 60 degrees...

-- Bruce

[Denis Flament]

Mark James Boyd wrote:


> C'mon, is that really true? How did he prove he was
> still in the "aerodyne" when the barograph got its highest
> altitude? Maybe he was just a big piece of hail.
> My gosh, maybe he used the baro to tell his altitude
> to make sure he didn't pull his chute too early...LOL

Well, the record may have been validated as a free fall altitude loss by
the International Parajumping Commission ;-)

--
Denis
Private replies: remove "moncourrielest" from my e-mail address
Pour me répondre utiliser l'adresse courriel figurant après
moncourrielest" dans mon adresse courriel...

[Jim]

Well, the relationship of flutter to IAS and TAS is certainly a
puzzle to me.

Somewhere I got the understanding that IAS, in a sense, indicates the
impact rate (pressure) of molecules on the aircraft, and thus in
thinner air an aircraft will "actually" (TAS) be flying faster to
receive the same air molecule impact rate (pressure).

TAS, on the other hand, indicates, in a sense, indicates the speed
at which the air molecules are moving past the aircraft - something
quite independent of just how MANY air molecules are passing by
the aircraft in a given amount of time.

Further, I have had the impression that flutter is a consequence of
the speed of the aircraft through the air (molecules) (TAS) rather
than the number of air molecules that happen to be impacting the
aircraft in a given amount of time (IAS).

So, I have always considered it prudent to view VNE due to FLUTTER
to be a TAS airspeed, not an IAS airspeed.

Have I been wrong about this?

[F.L. Whiteley]

"Jim" > wrote in message
...
> Well, the relationship of flutter to IAS and TAS is certainly a
> puzzle to me.
>
> Somewhere I got the understanding that IAS, in a sense, indicates the
> impact rate (pressure) of molecules on the aircraft, and thus in
> thinner air an aircraft will "actually" (TAS) be flying faster to
> receive the same air molecule impact rate (pressure).
>
True AFAIK, and the effectiveness of controls responds to this pressure.
Control flutter limitations are a function of IAS. Some sailplanes have
been designed with and even retrofitted with dampers. Bear in mind that
age, wear, repair, compromised mass balances, and paint can impact this.
(Not mutually exclusive changes)

> TAS, on the other hand, indicates, in a sense, indicates the speed
> at which the air molecules are moving past the aircraft - something
> quite independent of just how MANY air molecules are passing by
> the aircraft in a given amount of time.
>
Yes, and the center of pressure that generates lift shifts as a result and
may twist (maybe better un-twist) the wing. IIRC, the FL500 Grob had an
extra lamination or two of glass in the wings so it could fly faster than
stall speed at extreme altitude. In my DG-100 at speeds >120kts under
3000m, the amount of downward deflection at the tips was really impressive
and a bit unnerving. I don't recall similar deflection at 8500m at similar
TAS, but, like most everyone else, I have little empirical evidence.

> Further, I have had the impression that flutter is a consequence of
> the speed of the aircraft through the air (molecules) (TAS) rather
> than the number of air molecules that happen to be impacting the
> aircraft in a given amount of time (IAS).
>
Flutter in an elastic mode and is dependent on wing design. As I understand
it, a Lear Jet's Vne is based on IAS with Mach limits. The wings are quite
short and stiff compared to a sailplane, and have greater torsional
resistence by design. The twist in glider wings is there to provide more
benign handling, however, as in the OSTIV paper I've referenced previously,
sailplane design is a compromise of performance and engineering. The
elastic mode may be the limiting factor and engineering a sailplane to
perform at altitude as a Lear Jet would increase both weight and cost
unacceptably (unless your name is Fossett maybe). Since the sailplane
spends 99% of it's service life <6000m and a Lear Jet spends 90% of its
service life >8000m, each is designed appropriately.

>
> So, I have always considered it prudent to view VNE due to FLUTTER
> to be a TAS airspeed, not an IAS airspeed.
>
Perfectly safe as a conservative view.
>
> Have I been wrong about this?
>
The conjecture in the OSTIV paper was that (IAS+TAS)/2 was safe and that
this envelope might extend to 0.8 * TAS. However, there are a couple of
Nimbus 4 incidents that might suggest adoption of the prudent view. There
are also some 15m designs with little twist and stiff wings that might be
real rocket rides. I have a little time in a Jantar Std 2 and found it
nimble, a bit stiff, and honest in performance. I also found that things
like the aileron hinges wear a bit more quickly than some other gliders, so
pressure effects might be of interest. Too many factors and not enough
evidence to say who's right or wrong or taking unacceptable risks. The
third mode of flutter is pilot induced. Control inputs at high altitude and
speed could potentially induce either of the other two modes, I suppose.

Anyway, that's my take,

Frank Whiteley
Colorado

[Eric Greenwell]

Jim wrote:

> So, I have always considered it prudent to view VNE due to FLUTTER
> to be a TAS airspeed, not an IAS airspeed.
>
> Have I been wrong about this?

No, it is prudent, but as several have pointed out, it may be
unnecessarily conservative. That's because the flutter usually occurs
somewhere between IAS and TAS, and not strictly by TAS.

Personally, I'd use TAS on "older" (designed/certified 20+ years ago)
gliders, and the glider's handbook for "newer" (designed/certified
within the last 10 or so years, unless I knew specifically what the
older glider was designed and tested to. My reasoning is the older
certifications were not as stringent in this area as they are now.

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

Eric Greenwell
Washington State
USA

[Jack Harkin]

It is a TAS, this is the reason it occurs at a lower IAS as the altitude
increases. Without some sort of sophisticated computations it is very
difficult to determine TAS. IAS is easy to see and use.

[Webmaster Patagonia Soaring]

> H. Miranda World Record technique:
>
> 1. Fill wings with water

The Jantar that Horacio flight, DIDN'T HAVE WATER!!!!!

They flew using the 1 and 2 wave of cordillera del viento starting at
5000 meters (16666 ft) climb to 6000 m (20000 ft) and finish at 4400
meters (14666 ft). His maximum ground speed was 413 km/h (223 kts). I
have the IGC file for this record. I can e-mail you if you wish. The
jantar VNE is 275 kph (148 kts) at sea level.

Last year I flew with Horacio in the same triangle in a IS-28B2. Our
maximum ground speed was 330 kph (178kts) flying always at 160 kpn (86
kts) IAS, that is a little less that the IAS VNE for this altitude.
The VNE at sea level for the IS is 220 kph (118 kts)

Best regars,

Luis Briones