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wdaniell.longport(at)gmai
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 Posted: Mon Jan 01, 2018 6:16 pm Post subject: Are Vne and Va IAS or TAS? |
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I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
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peterz(at)zutrasoft.com
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| Posted: Mon Jan 01, 2018 6:29 pm Post subject: Are Vne and Va IAS or TAS? |
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TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
|
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peterz(at)zutrasoft.com
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| Posted: Mon Jan 01, 2018 6:40 pm Post subject: Are Vne and Va IAS or TAS? |
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Oops.... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
|
|
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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wdaniell.longport(at)gmai
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| Posted: Mon Jan 01, 2018 7:19 pm Post subject: Are Vne and Va IAS or TAS? |
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Mmmm....why the difference? The way I read the article it says that TAS is the critical value. For most pilot this discussion is irrelevant because the real issue occurs at altitude. However since we all fly here regularly at over 12k often in mountain turbulence this is very relevant.
Anyway luckily my dynon shows IAS TAS and GS and for now I'll stick with TAS as the key value.
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 21:43, "Pete" <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote: | Quote: |
Oops... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
|
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| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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wdaniell.longport(at)gmai
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| Posted: Wed Jan 03, 2018 4:23 am Post subject: Are Vne and Va IAS or TAS? |
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Pete
I found this http://www.australianflying.com.au/news/vne-and-flutter-explained
What do you think think?
Will
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 22:19, "William Daniell" <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote: | Quote: | Mmmm....why the difference? The way I read the article it says that TAS is the critical value. For most pilot this discussion is irrelevant because the real issue occurs at altitude. However since we all fly here regularly at over 12k often in mountain turbulence this is very relevant.
Anyway luckily my dynon shows IAS TAS and GS and for now I'll stick with TAS as the key value.
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 21:43, "Pete" <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote: | Quote: |
Oops.... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
|
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| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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JonSmith
Joined: 21 May 2010
Posts: 110
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| Posted: Wed Jan 03, 2018 5:20 am Post subject: Re: Are Vne and Va IAS or TAS? |
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My very simplistic schoolboy way of looking at it is like this:
VNE - the criteria is the SPEED at which the air molecules pass over the surfaces but not particularly the amount of them. Hence it’s the actual speed through the air (True Air Speed) that is relevant.
ASI actual reading is determined by the pressure of the air molecules in the pitot tube - which amongst other factors is determined by altitude. For a given true air speed (actual speed through the air) the higher up you are the less air molecules there are so the lower the ASI reads. (Or the other way around, for a given IAS, the higher you climb the greater the TAS will be). For the same reason the stalling speed is related to IAS and not TAS - amongst other variables it’s the VOLUME of air molecules passing over the wing that keeps it flying, not just the speed of them!
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peterz(at)zutrasoft.com
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| Posted: Thu Jan 04, 2018 1:44 pm Post subject: Are Vne and Va IAS or TAS? |
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Great article Will, thx!
I wonder now how the europa was tested wrt Vne and if Vd was tested/is specified, if there is a IAS/density altitude table, and if the the published Vne is structural or flutter?
Is Ivan lurking? 
Cheers,
Pete
On Jan 3, 2018, at 7:23 AM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | Pete
I found this http://www.australianflying.com.au/news/vne-and-flutter-explained
What do you think think?
Will
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 22:19, "William Daniell" <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote: | Quote: | Mmmm....why the difference? The way I read the article it says that TAS is the critical value. For most pilot this discussion is irrelevant because the real issue occurs at altitude. However since we all fly here regularly at over 12k often in mountain turbulence this is very relevant.
Anyway luckily my dynon shows IAS TAS and GS and for now I'll stick with TAS as the key value.
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 21:43, "Pete" <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote: | Quote: |
Oops.... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
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| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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ward.t(at)xtra.co.nz
Guest
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| Posted: Thu Jan 04, 2018 2:01 pm Post subject: Are Vne and Va IAS or TAS? |
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I am sure Peter Clark would have done those manoeuvres in the flight testing. Must look at his notes again.
Tim
Sent from my iPhone
Tim Ward
12 Waiwetu Street
Fendalton
CHRISTCHURCH 8052
Hom 03315166
On 5/01/2018, at 10:43 AM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
Great article Will, thx!
I wonder now how the europa was tested wrt Vne and if Vd was tested/is specified, if there is a IAS/density altitude table, and if the the published Vne is structural or flutter?
Is Ivan lurking?
Cheers,
Pete
On Jan 3, 2018, at 7:23 AM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | Pete
I found this http://www.australianflying.com.au/news/vne-and-flutter-explained
What do you think think?
Will
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 22:19, "William Daniell" <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote: | Quote: | Mmmm....why the difference? The way I read the article it says that TAS is the critical value. For most pilot this discussion is irrelevant because the real issue occurs at altitude. However since we all fly here regularly at over 12k often in mountain turbulence this is very relevant.
Anyway luckily my dynon shows IAS TAS and GS and for now I'll stick with TAS as the key value.
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 21:43, "Pete" <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote: | Quote: |
Oops.... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
|
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| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
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ivanshaw(at)btinternet.co
Guest
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| Posted: Thu Jan 04, 2018 2:22 pm Post subject: Are Vne and Va IAS or TAS? |
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All our company aircraft were tested to Vd, 10% over Vne. And not just taken to the speed but then tested [short stick and rudder raps] to see if any flutter mode could be excited at Vd. I have performed these tests at/up to 8000ft . We have never experienced any flutter mode. I also tested the tail plane underbalanced and over balanced with the same results. To my knowledge we have not had any reported flutter incidence on the entire fleet. As you mentioned Pete did exceed Vd on a few occasions.
Ivan
From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Tim Ward
Sent: 04 January 2018 22:01
To: europa-list(at)matronics.com
Subject: Re: Are Vne and Va IAS or TAS?
I am sure Peter Clark would have done those manoeuvres in the flight testing. Must look at his notes again.
Tim
Sent from my iPhone
Tim Ward
12 Waiwetu Street
Fendalton
CHRISTCHURCH 8052
Hom 03315166
On 5/01/2018, at 10:43 AM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
Great article Will, thx!
I wonder now how the europa was tested wrt Vne and if Vd was tested/is specified, if there is a IAS/density altitude table, and if the the published Vne is structural or flutter?
Is Ivan lurking?
Cheers,
Pete
On Jan 3, 2018, at 7:23 AM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: |
Pete
I found this http://www.australianflying.com.au/news/vne-and-flutter-explained
What do you think think?
Will
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 22:19, "William Daniell" <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote: | Quote: |
Mmmm....why the difference? The way I read the article it says that TAS is the critical value. For most pilot this discussion is irrelevant because the real issue occurs at altitude. However since we all fly here regularly at over 12k often in mountain turbulence this is very relevant.
Anyway luckily my dynon shows IAS TAS and GS and for now I'll stick with TAS as the key value.
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 21:43, "Pete" <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote: | Quote: |
Oops.... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: |
I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
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| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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grahamsingleton(at)btinte
Guest
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| Posted: Thu Jan 04, 2018 2:32 pm Post subject: Are Vne and Va IAS or TAS? |
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Jon
slight adjustment, air molecules don't have volume, it's the Mass that counts I think.
Graham
On Thursday, 4 January 2018, 22:22, "ivanshaw(at)btinternet.com" <ivanshaw(at)btinternet.com> wrote:
#yiv3280697347 #yiv3280697347 -- _filtered #yiv3280697347 {panose-1:2 4 5 3 5 4 6 3 2 4;} _filtered #yiv3280697347 {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;} #yiv3280697347 #yiv3280697347 p.yiv3280697347MsoNormal, #yiv3280697347 li.yiv3280697347MsoNormal, #yiv3280697347 div.yiv3280697347MsoNormal {margin:0cm;margin-bottom:.0001pt;font-size:11.0pt;} #yiv3280697347 a:link, #yiv3280697347 span.yiv3280697347MsoHyperlink {color:blue;text-decoration:underline;} #yiv3280697347 a:visited, #yiv3280697347 span.yiv3280697347MsoHyperlinkFollowed {color:purple;text-decoration:underline;} #yiv3280697347 p.yiv3280697347msonormal0, #yiv3280697347 li.yiv3280697347msonormal0, #yiv3280697347 div.yiv3280697347msonormal0 {margin-right:0cm;margin-left:0cm;font-size:11.0pt;} #yiv3280697347 span.yiv3280697347EmailStyle18 {color:windowtext;} #yiv3280697347 .yiv3280697347MsoChpDefault {font-size:10.0pt;} _filtered #yiv3280697347 {margin:72.0pt 72.0pt 72.0pt 72.0pt;} #yiv3280697347 div.yiv3280697347WordSection1 {} #yiv3280697347 All our company aircraft were tested to Vd, 10% over Vne. And not just taken to the speed but then tested [short stick and rudder raps] to see if any flutter mode could be excited at Vd. I have performed these tests at/up to 8000ft . We have never experienced any flutter mode. I also tested the tail plane underbalanced and over balanced with the same results. To my knowledge we have not had any reported flutter incidence on the entire fleet. As you mentioned Pete did exceed Vd on a few occasions.
Ivan
From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Tim WardSent: 04 January 2018 22:01To: europa-list(at)matronics.comSubject: Re: Are Vne and Va IAS or TAS?
I am sure Peter Clark would have done those manoeuvres in the flight testing. Must look at his notes again.
Tim Sent from my iPhone
Tim Ward
12 Waiwetu Street
Fendalton
CHRISTCHURCH 8052
Hom 03315166
On 5/01/2018, at 10:43 AM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: | Great article Will, thx!
I wonder now how the europa was tested wrt Vne and if Vd was tested/is specified, if there is a IAS/density altitude table, and if the the published Vne is structural or flutter?
Is Ivan lurking?
Cheers,
Pete
On Jan 3, 2018, at 7:23 AM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | Pete
I found this http://www.australianflying.com.au/news/vne-and-flutter-explained
What do you think think?
Will
William DaniellLONGPORT+57 310 295 0744
On Jan 1, 2018 22:19, "William Daniell" <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | Mmmm....why the difference? The way I read the article it says that TAS is the critical value. For most pilot this discussion is irrelevant because the real issue occurs at altitude. However since we all fly here regularly at over 12k often in mountain turbulence this is very relevant.
Anyway luckily my dynon shows IAS TAS and GS and for now I'll stick with TAS as the key value.
William DaniellLONGPORT+57 310 295 0744
On Jan 1, 2018 21:43, "Pete" <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: | Oops.... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: | TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: | I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
|
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| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
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peterz(at)zutrasoft.com
Guest
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| Posted: Thu Jan 04, 2018 2:44 pm Post subject: Are Vne and Va IAS or TAS? |
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Many thanks Ivan! That is comforting to know (and i'm not surprised
Any idea what was done with the glider wings? They would be a good candidate for an IAS/density alt table 
Thx again!
Pete
On Jan 4, 2018, at 5:21 PM, <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> wrote:
| Quote: | <![endif]--> <![endif]-->
All our company aircraft were tested to Vd, 10% over Vne. And not just taken to the speed but then tested [short stick and rudder raps] to see if any flutter mode could be excited at Vd. I have performed these tests at/up to 8000ft . We have never experienced any flutter mode. I also tested the tail plane underbalanced and over balanced with the same results. To my knowledge we have not had any reported flutter incidence on the entire fleet. As you mentioned Pete did exceed Vd on a few occasions.
Ivan
From: owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com) [mailto:owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com)] On Behalf Of Tim Ward
Sent: 04 January 2018 22:01
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Subject: Re: Are Vne and Va IAS or TAS?
I am sure Peter Clark would have done those manoeuvres in the flight testing. Must look at his notes again.
Tim
Sent from my iPhone
Tim Ward
12 Waiwetu Street
Fendalton
CHRISTCHURCH 8052
Hom 03315166
On 5/01/2018, at 10:43 AM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
Great article Will, thx!
I wonder now how the europa was tested wrt Vne and if Vd was tested/is specified, if there is a IAS/density altitude table, and if the the published Vne is structural or flutter?
Is Ivan lurking?
Cheers,
Pete
On Jan 3, 2018, at 7:23 AM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: |
Pete
I found this http://www.australianflying.com.au/news/vne-and-flutter-explained
What do you think think?
Will
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 22:19, "William Daniell" <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote: | Quote: |
Mmmm....why the difference? The way I read the article it says that TAS is the critical value. For most pilot this discussion is irrelevant because the real issue occurs at altitude. However since we all fly here regularly at over 12k often in mountain turbulence this is very relevant.
Anyway luckily my dynon shows IAS TAS and GS and for now I'll stick with TAS as the key value.
William Daniell
LONGPORT
+57 310 295 0744
On Jan 1, 2018 21:43, "Pete" <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote: | Quote: |
Oops.... I mis-stated. VNE=TAS. Va=IAS
On Jan 1, 2018, at 9:29 PM, Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> wrote:
| Quote: |
TAS from my research.
https://www.vansaircraft.com/pdf/hp_limts.pdf
Cheers,
Pete
On Jan 1, 2018, at 9:15 PM, William Daniell <wdaniell.longport(at)gmail.com (wdaniell.longport(at)gmail.com)> wrote:
| Quote: |
I seem to recall a discussion on this but I can't find it on the list.
At 12000 ft DA at which I was flying today, the difference is between IAS and TAS is 20 kts or roughly 20%.
Thanks in advance Will
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peterz(at)zutrasoft.com
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| Posted: Thu Jan 04, 2018 2:49 pm Post subject: Are Vne and Va IAS or TAS? |
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Hi Ivan, just to confirm, Vd IAS (at)8000ft DA?
Thanks again!
Pete
On Jan 4, 2018, at 5:21 PM, <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> wrote:
| Quote: | <![endif]--> <![endif]-->
All our company aircraft were tested to Vd, 10% over Vne. And not just taken to the speed but then tested [short stick and rudder raps] to see if any flutter mode could be excited at Vd. I have performed these tests at/up to 8000ft . We have never experienced any flutter mode. I also tested the tail plane underbalanced and over balanced with the same results. To my knowledge we have not had any reported flutter incidence on the entire fleet. As you mentioned Pete did exceed Vd on a few occasions.
Ivan
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budyerly(at)msn.com
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| Posted: Thu Jan 04, 2018 7:16 pm Post subject: Are Vne and Va IAS or TAS? |
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Yep Graham,
Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
Bottom line, what you read on the airspeed indicator counts. TAS is important (actually Mach number) as the skin heats up due to friction which is a different ball of wax. I was always a slow speed aero guy to match my mind
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JonSmith
Joined: 21 May 2010
Posts: 110
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| Posted: Fri Jan 05, 2018 2:30 am Post subject: Re: Are Vne and Va IAS or TAS? |
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| budyerly(at)msn.com wrote: | Yep Graham,
Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is � Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
Bottom line, what you read on the airspeed indicator counts. |
Hi Bud, scenario: flying at 10,000’ with standard pressure and temperature with IAS of 165kts the TAS calculates to be 190kts. Are you saying that is OK? Currently I feel not. I’m always open to (non technical!) well reasoned persuasion and argument but even despite Ivans’s welcoming and comforting story about the flutter trials I would have thought this puts one into unknown territory. Agreed that structural issues are related to IAS but I feel that specifically, flutter issues relate to the actual speed with which particles pass by!
HOWEVER - if the design and testing criteria is that the VNE is based on IAS and that flutter is proven not to occur at any TAS that could concievably be reached at that maximum IAS then I guess that my thinking about VNE (whilst conservative) has been wrong!
My opinion was from my gliding days where in mountain wave conditions we could get very high, circa 25,000’. Sometimes we would descend afterwards from high altitude at high speed to lose height; with VNE of 135kts common in gliders the TAS could be extremely high - up to 200kts! I’m sure I can remember some glider’s flight manuals warning of this and that VNE was TAS based - but it was a long time ago!
Graham - thanks for that. “Mass” sounds better! I said I was at schoolboy level. But a schoolboy would have known that so I am below that level even! I was referring to the amount or number of molecules and yes, mass is better than volume!
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wdaniell.longport(at)gmai
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| Posted: Fri Jan 05, 2018 1:04 pm Post subject: Are Vne and Va IAS or TAS? |
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BudDoes this apply even at the upper altitude range ....say 13k or 15k?
Will
On Jan 4, 2018 22:19, "Bud Yerly" <budyerly(at)msn.com (budyerly(at)msn.com)> wrote: | Quote: |
Yep Graham,
Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is ½ Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
Bottom line, what you read on the airspeed indicator counts. TAS is important (actually Mach number) as the skin heats up due to friction which is a different ball of wax. I was always a slow speed aero guy to match my mind.
Regards,
Bud Yerly
Sent from Mail for Windows 10
From: owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com) <owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com)> on behalf of Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)>
Sent: Thursday, January 4, 2018 5:49:37 PM
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Subject: Re: Are Vne and Va IAS or TAS?
Hi Ivan, just to confirm, Vd IAS (at)8000ft DA?
Thanks again!
Pete
On Jan 4, 2018, at 5:21 PM, <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> wrote:
| Quote: |
All our company aircraft were tested to Vd, 10% over Vne. And not just taken to the speed but then tested [short stick and rudder raps] to see if any flutter mode could be excited at Vd. I have performed these tests at/up to 8000ft . We have never experienced any flutter mode. I also tested the tail plane underbalanced and over balanced with the same results. To my knowledge we have not had any reported flutter incidence on the entire fleet. As you mentioned Pete did exceed Vd on a few occasions.
Ivan
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davidjoyce(at)doctors.org
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| Posted: Fri Jan 05, 2018 3:13 pm Post subject: Are Vne and Va IAS or TAS? |
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I can happily accept that IAS is what matters in relation to flutter at any height, but there is another aspect where I suspect that TAS becomes more relevant. If you set out to do say a rate 1 turn at altitude you are going to have to bank more steeply and pull more g and come closer to a stall than would be the case at the same IAS at lower altitudes. In most circumstances that wouldn't matter too much, but I guess it means that as you go up a mountain valley you need progressively more lateral,space to do an escape 180 turn, (whilst the valley is probably getting progressively narrower)
Regards, David Joyce, GXSDJ
On 2018-01-05 21:03, William Daniell wrote: | Quote: | Bud Does this apply even at the upper altitude range ....say 13k or 15k?
Will
On Jan 4, 2018 22:19, "Bud Yerly" <budyerly(at)msn.com (budyerly(at)msn.com)> wrote: | Quote: |
Yep Graham,
Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
Bottom line, what you read on the airspeed indicator counts. TAS is important (actually Mach number) as the skin heats up due to friction which is a different ball of wax. I was always a slow speed aero guy to match my mind.
Regards,
Bud Yerly
Sent from Mail for Windows 10
From: owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com) <owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com)> on behalf of Pete <peterz(at)zutrasoft.com (peterz(at)zutrasoft.com)> Sent: Thursday, January 4, 2018 5:49:37 PM To: europa-list(at)matronics.com (europa-list(at)matronics.com) Subject: Re: Are Vne and Va IAS or TAS?
Hi Ivan, just to confirm, Vd IAS (at)8000ft DA?
Thanks again!
Pete
On Jan 4, 2018, at 5:21 PM, <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> <ivanshaw(at)btinternet.com (ivanshaw(at)btinternet.com)> wrote:
| Quote: |
All our company aircraft were tested to Vd, 10% over Vne. And not just taken to the speed but then tested [short stick and rudder raps] to see if any flutter mode could be excited at Vd. I have performed these tests at/up to 8000ft . We have never experienced any flutter mode. I also tested the tail plane underbalanced and over balanced with the same results. To my knowledge we have not had any reported flutter incidence on the entire fleet. As you mentioned Pete did exceed Vd on a few occasions.
Ivan
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budyerly(at)msn.com
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| Posted: Sun Jan 07, 2018 8:10 pm Post subject: Are Vne and Va IAS or TAS? |
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Will,
I'm still on the road but here goes.
Short answer:
Q is force, whereas True is just speed.
Long Answer:
Think of it this way. The mono cruises at 175 TAS at 18,000 with a 914. The indicated is only 125 ish. You cannot pull enough G to achieve 6 Gs before you stall or have a vertical gust break the plane. Is the mono above VNE, at 175 TAS, NO. Heck you are not at Vno or about 131 KIAS which is your green arc for gust factor(turbulent speed).
That gust factor is what you need to be aware of in the turbulence of the mountains.
"Aircraft Performance" by Domash explains it.
So does the FAA. For finding high speed affects, the USAF F104 VN diagram is on Wikipedia and shows how Mach affects figure in for high TAS.
TAS is important in turn rate, radius, navigation, and determining your Mach and Q velocity. But it is your Q (dynamic pressure), aka IAS, that affects, flutter, structural deformation, and your stall and not to exceed speeds. This means what you read on your airspeed indicator is what you need to know for the plane. TAS and Ground Speed affect your pilotage which is a different topic.
Again, in mountain flying, you need to know your turn diameter when valley flying, high altitude patterns (wider pattern necessary), lead turns to a radials etc. (especially In high speed aircraft) and in light aircraft in very high elevations. Engine performance vs airspeed bleed off becomes a factor as well.
Regards,
Bud Yerly
Custom Flight Creations
From: William Daniell
Sent: Friday, January 5, 4:07 PM
Subject: RE: Are Vne and Va IAS or TAS?
To: europa-list(at)matronics.com
Bud
Does this apply even at the upper altitude range ....say 13k or 15k?
Will
On Jan 4, 2018 22:19, "Bud Yerly" <budyerly<mailto:budyerly(at)msn.com>(at)msn.com<mailto:budyerly(at)msn.com>> wrote:
Yep Graham,
Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
Bottom line, what you read on the airspeed indicator counts. TAS is important (actually Mach number) as the skin heats up due to friction which is a different ball of wax. I was always a slow speed aero guy to match my mind
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wdaniell.longport(at)gmai
Guest
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| Posted: Tue Jan 09, 2018 4:08 am Post subject: Are Vne and Va IAS or TAS? |
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Bud thanks, sets my mind at rest.
William Daniell
LONGPORT
+57 310 295 0744
On Sun, Jan 7, 2018 at 11:09 PM, Bud Yerly <budyerly(at)msn.com (budyerly(at)msn.com)> wrote:
| Quote: | Will,
I'm still on the road but here goes.
Short answer:
Q is force, whereas True is just speed.
Long Answer:
Think of it this way. The mono cruises at 175 TAS at 18,000 with a 914. The indicated is only 125 ish. You cannot pull enough G to achieve 6 Gs before you stall or have a vertical gust break the plane. Is the mono above VNE, at 175 TAS, NO. Heck you are not at Vno or about 131 KIAS which is your green arc for gust factor(turbulent speed).
That gust factor is what you need to be aware of in the turbulence of the mountains.
"Aircraft Performance" by Domash explains it.
So does the FAA. For finding high speed affects, the USAF F104 VN diagram is on Wikipedia and shows how Mach affects figure in for high TAS.
TAS is important in turn rate, radius, navigation, and determining your Mach and Q velocity. But it is your Q (dynamic pressure), aka IAS, that affects, flutter, structural deformation, and your stall and not to exceed speeds. This means what you read on your airspeed indicator is what you need to know for the plane. TAS and Ground Speed affect your pilotage which is a different topic.
Again, in mountain flying, you need to know your turn diameter when valley flying, high altitude patterns (wider pattern necessary), lead turns to a radials etc. (especially In high speed aircraft) and in light aircraft in very high elevations. Engine performance vs airspeed bleed off becomes a factor as well.
Regards,
Bud Yerly
Custom Flight Creations
From: William Daniell
Sent: Friday, January 5, 4:07 PM
Subject: RE: Are Vne and Va IAS or TAS?
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Bud
Does this apply even at the upper altitude range ....say 13k or 15k?
Will
On Jan 4, 2018 22:19, "Bud Yerly" <budyerly (budyerly(at)msn.com)(at)msn.com (budyerly(at)msn.com)> wrote:
| Quote: | Yep Graham,
Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is ½ Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
Bottom line, what you read on the airspeed indicator counts. TAS is important (actually Mach number) as the skin heats up due to friction which is a different ball of wax. I was always a slow speed aero guy to match my mind.
Regards,
Bud Yerly
Sent from Mail for Windows 10
From: owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com) <owner-europa-list-server(at)matronics.com (owner-europa-list-server(at)matronics.com)> on behalf of Pete <peterz (peterz(at)zutrasoft.com)(at)zutrasoft.com (peterz(at)zutrasoft.com)>
Sent: Thursday, January 4, 2018 5:49:37 PM
To: europa-list(at)matronics.com (europa-list(at)matronics.com)
Subject: Re: Are Vne and Va IAS or TAS?
Hi Ivan, just to confirm, Vd IAS (at)8000ft DA?
Thanks again!
Pete
On Jan 4, 2018, at 5:21 PM, <ivanshaw (ivanshaw(at)btinternet.com)(at)btinternet.com (ivanshaw(at)btinternet.com)> <ivanshaw (ivanshaw(at)btinternet.com)(at)btinternet.com (ivanshaw(at)btinternet.com)> wrote:
| Quote: | All our company aircraft were tested to Vd, 10% over Vne. And not just taken to the speed but then tested [short stick and rudder raps] to see if any flutter mode could be excited at Vd. I have performed these tests at/up to 8000ft . We have never experienced any flutter mode. I also tested the tail plane underbalanced and over balanced with the same results. To my knowledge we have not had any reported flutter incidence on the entire fleet. As you mentioned Pete did exceed Vd on a few occasions.
Ivan
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peterz(at)zutrasoft.com
Guest
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| Posted: Tue Jan 09, 2018 9:34 am Post subject: Are Vne and Va IAS or TAS? |
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Not to be argumentative, but as i understand it, Bud's explanation ignores the issue reported/described in the other articles, namely that at altitude there is less flutter damping for the same reasons Bud explains wrt the structural limits. So for flutter specifically it is TAS that is the determining limit, and not IAS. Taken to the extreme, the U2 sometimes operates near "coffin corner" where flutter speed is very near stall speed (IAS is indicating near stall, but they are so high and the air so thin that they are near the risk of flutter). It is also why the http://www.perlanproject.org/ glider is heavily instrumented to detect the onset of flutter as they go higher and higher in their record attempts.
Taht said, it is comforting to know that Ivan has tested Vd with stick excitation to 8000 feet, so i would assume that this could be used as the derating baseline when going to higher TAS's.
Cheers,
Pete
A239
[quote] On Jan 9, 2018, at 7:08 AM, William Daniell <wdaniell.longport(at)gmail.com> wrote:
Bud thanks, sets my mind at rest.
William Daniell
LONGPORT
+57 310 295 0744
> On Sun, Jan 7, 2018 at 11:09 PM, Bud Yerly <budyerly(at)msn.com> wrote:
> Will,
> I'm still on the road but here goes.
> Short answer:
> Q is force, whereas True is just speed.
> Long Answer:
> Think of it this way. The mono cruises at 175 TAS at 18,000 with a 914. The indicated is only 125 ish. You cannot pull enough G to achieve 6 Gs before you stall or have a vertical gust break the plane. Is the mono above VNE, at 175 TAS, NO. Heck you are not at Vno or about 131 KIAS which is your green arc for gust factor(turbulent speed).
>
> That gust factor is what you need to be aware of in the turbulence of the mountains.
>
> "Aircraft Performance" by Domash explains it.
> So does the FAA. For finding high speed affects, the USAF F104 VN diagram is on Wikipedia and shows how Mach affects figure in for high TAS.
>
> TAS is important in turn rate, radius, navigation, and determining your Mach and Q velocity. But it is your Q (dynamic pressure), aka IAS, that affects, flutter, structural deformation, and your stall and not to exceed speeds. This means what you read on your airspeed indicator is what you need to know for the plane. TAS and Ground Speed affect your pilotage which is a different topic.
>
> Again, in mountain flying, you need to know your turn diameter when valley flying, high altitude patterns (wider pattern necessary), lead turns to a radials etc. (especially In high speed aircraft) and in light aircraft in very high elevations. Engine performance vs airspeed bleed off becomes a factor as well.
>
> Regards,
>
> Bud Yerly
> Custom Flight Creations
>
>
>
> From: William Daniell
> Sent: Friday, January 5, 4:07 PM
> Subject: RE: Are Vne and Va IAS or TAS?
> To: europa-list(at)matronics.com
>
>
> Bud
> Does this apply even at the upper altitude range ....say 13k or 15k?
> Will
>
>
>> On Jan 4, 2018 22:19, "Bud Yerly" <budyerly(at)msn.com> wrote:
>> Yep Graham,
>> Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is ½ Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
>>
>> Bottom line, what you read on the airspeed indicator counts. TAS is important (actually Mach number) as the skin heats up due to friction which is a different ball of wax. I was always a slow speed aero guy to match my mind
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budyerly(at)msn.com
Guest
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| Posted: Wed Jan 10, 2018 1:15 pm Post subject: Are Vne and Va IAS or TAS? |
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Pete,
Short answer:
The U2 and coffin corner are at altitudes and airspeeds the Europa can never achieve... Therefore not relevant to mountain flying in a Europa. Or any flight operation of a GA light propeller driven aircraft for that manner. The physiological limit of 25,000 feet without pressure breathing oxygen or cabin pressure and 50,000 foot limit without pressure suits, kind of limits the Europa and its owners from fearing any of these effects.
I prefer to believe the aerodynamicists on control design. Flutter is often discussed and considered to be only the control surface moving by the non aerodynamicist, when the torsional rigidity of the wing, or control linkage, or tab attachment, is the actual effect. Pilots feel vibration and report it as flutter. From where, they dont know, it has to be found out. TAS is a component of the dynamic pressure or q = (1/2 density x V squared) and the effect of q on the wing and the air speed itself can be explained below. A Europa in orbit at 25000 mph has no flutter problems as it has no air molecules. Without air molecules there is no air mass. No air mass, no aerodynamics. Mass of the air (viscosity, temp, etc. ) must always be considered. Not just speed.
Long answer:
Re: Coffin corner.
Coffin corner is operating between critical Mach number and Stall equivalent airspeed. It is true that at 90 and 100 thousand feet, a subsonic slow flying aircraft (even a glider in a dive I suppose) with proper propulsion (uplift to get there and then dive) can get so high it is near the speed of sound even though it is near stall. Air liners at their operational limit can be there also as they cruise at .86 Mach or so. Supersonic designs are exempt from this. They just stall below transonic region at high altitude or fly supersonic and not stall at all at very high altitude.
As you all know, Mach number is simply V/Va or the ratio of TAS speed divided by the speed of sound.
The speed of sound is defined by the square root of specific heat of air x gRT with Temperature being the largest component of change. So its really cold at from 35,000-100,000 feet and the speed of sound is fairly constant in that range at about -55C or about 575KTAS. Air density of course is extremely small. So to get indicated airspeed high enough to fly (not stall due to lack of density), by default you must be getting closer to the Mach at the extremes of the atmosphere (from 45,000 you can feel the difference but much be much higher to see them close on a straight wing airplane).
Example: 90 KIAS required to fly at the stall at 80,000 feet with a jet powered drone, the true is 170 TAS, the mach is going to be about .3, so there is no technical coffin corner at 80K anywhere near the stall speed.
Critical Mach is the Mach number where the normal shock wave forms on the aircraft (normally the wing and fuselage juncture and the thickest part of a thick wing). In a U2 or T-33 that occurs about .86 Mach 45,000 feet, the indicated was 218 KIAS and 495TAS. Stall was about 120 KIAS. The cabin altitude was right at 25,000 so we couldnt go higher. Every subsonic airplane has a different reaction to the large separated flow behind the normal shock wave. The U2 and T33 had hydraulic controlled ailerons so no flutter or buzz possible on the wing. But the elevator control is severely affected by the separated flow of the shock wave. (Eventual loss of elevator control and nose pitch down.)
The flexible wing design of some airplanes (drones, gliders, and even some powered planes) have very poor torsional rigidity (they bend leading edge up and down easily with a vertical gust load or due to load deformation). In straight and level non accelerated flight, if a normal shock wave forms on the wing, the separated flow near mid chord, may cause the wing to twist, which changes the position of the shock wave, which changes the twist and a flutter will occur in the wing and the non boosted aileron will follow along, balanced or not. Turbulence exacerbates this problem due to the wings elastic effects. If only considering Mach crit, as the wing twists LE up (due to normal shock or turbulence), the lower side of the aileron will have pressure (due to normal flow) and the upper side not due to separated flow and that can force the aileron upward, causing the wing to twist more and divergence begins until torsional rigidity finally reacts and the wing twists hopefully back down, changing the shock wave position to the lower surface and it all starts again. The stick will move of course so aileron flutter is suspected when it is actually forced wing flutter. With aileron control input by the pilot at the same time, that twist effect can be quite large in flexible aircraft inviting very interesting effects. If operating a jet powered drone near the coffin corner, the pilot cant just pull up to slow down (hes at the stall) and cant lower the nose to pick up airspeed (hes seeing aeroelastic or Mach effects limiting control function) hence the name coffin corner. Only by deploying speed brakes and reducing power going to a lower altitude will recover the aircraft. Because the IAS at stall is a high TAS at very high altitude (50-100K), some have determined the affect of adverse aerodynamic affects to be because of TAS alone. That takes the TAS out of context and is a bit of a stretch to the actual potential cause of their aeroelastic problems and the dampening that increased density may afford. It takes air to have aeroelastic problems.
Re: Aeroelastic concerns:
An aircraft built to be non rigid must be flown and tested very carefully as any force outside of straight and level flight will have very serious effects. At very high altitudes, many high lift laminar airfoil designs have issues with the boundary layer separation and control effectiveness degradation occurs or wing twist due to the center of pressure shift the airfoil was not designed for (that is at weird Reynolds numbers ((a dimensionless number of 1.4 x density x V x length / viscosity of air that determines the boundary layer separation point))). At these extreme conditions, aeroelastic effects and boundary layer separation are pronounced in these flexible fliers operating near the stall in the cold thin air of higher altitude such as the Perlan Project. We have all seen the wing flutter test video of gliders encountering wing flutter, aileron reversing due to wing twist, etc. The effects of these problems are exacerbated at altitude and high TAS. The q is low and the TAS high so some believe the density is irrelevant. It is not. Temperature is also a problem, especially with the modulus of elasticity of carbon fiber. These types of aircraft are very light, but very flexible fliers and have to be thoroughly tested and instrumented due to the problems associated with aeroelastic and structural effects (as well as aileron deflection induced by separated flow and the affects of the low OAT). Or they have to be built heavy but rigid (i.e. the Europa). Aircraft designed for the long haul of normal operations tend to be quite stiff to avoid these problems and have long operational lives.
Finally on aileron flutter. From Dommash - Airplane Aerodynamics:
Precautions must be observed to prevent destructive flutter or undamped short-period oscillations of control surfaces. These precautions are related to mass balance about the hinge axis, static contour and changes of contour under air loads, and tightness of tab linkages.
Mass balance is balance the tab about the hinge axis. There is no rotative tendency to induce flutter from mass-inertia effects if the control is balance precisely on the hinge line. See the Europa build manual.
Contour Effects: All control surfaces should be flat sided or concave. Convex surfaces (flexible fabric that balloons under pressure ((GB racers of 1930s)) become unstable and begin an undamped oscillation. See build manual on contour.
Note: Spanwise torsional stiffness in a control surface may also cause flutter. Long or solid hinges and stiff construction are important in control design. The Europa ailerons have sufficient stiffness and are reasonably hinged to a rigid wing structure not prone in its flight envelope to aeroelastic effects.
So contour your ailerons to the foam shape. Balance them. Keep the hinges and linkages tight and maintained, pad the aileron quick disconnects with no slop, and flutter will not be a problem at any operational limit of the Europa, to include mountain flying up to 25,000 feet for sure. Dont fly over 25,000 unpressurized for any extended period, as it is a serious physiological limit to most people even on oxygen without pressure breathing. Fly your IAS within limits of the flight manual/POH and enjoy yourself.
If you want to design drones or manned gliders operating at 100K, that is a different type airplane flying in a different world. To date, only highly funded experimental aircraft fly near that regime.
Best Regards,
Bud Yerly
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
From: Pete<mailto:peterz(at)zutrasoft.com>
Sent: Tuesday, January 9, 2018 12:38 PM
To: europa-list(at)matronics.com<mailto:europa-list(at)matronics.com>
Subject: Re: Are Vne and Va IAS or TAS?
Not to be argumentative, but as i understand it, Bud's explanation ignores the issue reported/described in the other articles, namely that at altitude there is less flutter damping for the same reasons Bud explains wrt the structural limits. So for flutter specifically it is TAS that is the determining limit, and not IAS. Taken to the extreme, the U2 sometimes operates near "coffin corner" where flutter speed is very near stall speed (IAS is indicating near stall, but they are so high and the air so thin that they are near the risk of flutter). It is also why the http://www.perlanproject.org/<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.perlanproject.org%2F&data=02%7C01%7C%7C9d0911445d9649fb76b808d55787d448%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636511163254423256&sdata=J07iNvPuNgRaxf2BJeDJWAPgVCtpCC9rgT4PiYXpZzU%3D&reserved=0> glider is heavily instrumented to detect the onset of flutter as they go higher and higher in their record attempts.
That said, it is comforting to know that Ivan has tested Vd with stick excitation to 8000 feet, so i would assume that this could be used as the derating baseline when going to higher TAS's.
Cheers,
Pete
A239
On Jan 9, 2018, at 7:08 AM, William Daniell <wdaniell.longport(at)gmail.com<mailto:wdaniell.longport(at)gmail.com>> wrote:
Bud thanks, sets my mind at rest.
William Daniell
LONGPORT
+57 310 295 0744
On Sun, Jan 7, 2018 at 11:09 PM, Bud Yerly <budyerly(at)msn.com<mailto:budyerly(at)msn.com>> wrote:
Will,
I'm still on the road but here goes.
Short answer:
Q is force, whereas True is just speed.
Long Answer:
Think of it this way. The mono cruises at 175 TAS at 18,000 with a 914. The indicated is only 125 ish. You cannot pull enough G to achieve 6 Gs before you stall or have a vertical gust break the plane. Is the mono above VNE, at 175 TAS, NO. Heck you are not at Vno or about 131 KIAS which is your green arc for gust factor(turbulent speed).
That gust factor is what you need to be aware of in the turbulence of the mountains.
"Aircraft Performance" by Domash explains it.
So does the FAA. For finding high speed affects, the USAF F104 VN diagram is on Wikipedia and shows how Mach affects figure in for high TAS.
TAS is important in turn rate, radius, navigation, and determining your Mach and Q velocity. But it is your Q (dynamic pressure), aka IAS, that affects, flutter, structural deformation, and your stall and not to exceed speeds. This means what you read on your airspeed indicator is what you need to know for the plane. TAS and Ground Speed affect your pilotage which is a different topic.
Again, in mountain flying, you need to know your turn diameter when valley flying, high altitude patterns (wider pattern necessary), lead turns to a radials etc. (especially In high speed aircraft) and in light aircraft in very high elevations. Engine performance vs airspeed bleed off becomes a factor as well.
Regards,
Bud Yerly
Custom Flight Creations
From: William Daniell
Sent: Friday, January 5, 4:07 PM
Subject: RE: Are Vne and Va IAS or TAS?
To: europa-list(at)matronics.com<mailto:europa-list(at)matronics.com>
Bud
Does this apply even at the upper altitude range ....say 13k or 15k?
Will
On Jan 4, 2018 22:19, "Bud Yerly" <budyerly<mailto:budyerly(at)msn.com>(at)msn.com<mailto:budyerly(at)msn.com>> wrote:
Yep Graham,
Airplanes only feel air pressure, not the velocity of the molecule alone. Dynamic pressure is Density times Velocity Squared or IAS (actually you have calibrated then equivalent) is what the airplane feels. Those RV guys got all hung up on this and confused everyone.
Bottom line, what you read on the airspeed indicator counts. TAS is important (actually Mach number) as the skin heats up due to friction which is a different ball of wax. I was always a slow speed aero guy to match my mind
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