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TAS and VNE

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wnorth(at)sdccd.edu
Guest

Posted: Sun Mar 25, 2007 7:28 pm Post subject: TAS and VNE

I also don't entirely agree with the Kruger article.   

Flutter is not a function of velocity directly, it is a function of force acting upon the components which may flutter. While the air molecules are going by at a faster rate there are far less of them so the resultant force doesn't nearly increase at the rate TAS does with gains in altitude.  

Flutter is properly called negative dynamic stability and it requires positive static stability to occur. Positive static force pushes the control back to its neutral condition. When it's coupled to inertia and the resultant forces are able to move the control beyond that to a position greater then the original upset than that is negative dynamic stability AKA flutter. Mass aft of the pivot line adds to the inertia, mass at or just fwd of it takes away from the inertia. However it is force that causes the initial positive static desire to return to neutral and beyond. And it doesn't change too much with changes in altitude. If it did you would be able to notice it in the feel of the stick as altitude changed.  

This is one of the primary reasons we use VNE and all the other numbers in indicated units.    

W     [quote][b]

dennis.glaeser(at)eds.com
Guest

Posted: Mon Mar 26, 2007 6:39 am Post subject: TAS and VNE

I must respectfully disagree.  Flutter and dynamic stability are vastly

different things.  Flutter is NOT the trailing edge of a control surface

flapping in the breeze like a flag in high wind.  Flutter is the some

portion of an airframe (wing, tail, fuselage) acting like a rubber band

due to forces in resonance with one or more of it's natural frequencies.

Since it is a frequency, not force, related phenomenon, that is why TAS

is key instead of IAS.  At the right frequency, it only takes a small

force to start the process (think tuning fork).

The force that reacts to bring the airframe back after a disturbance is

the stiffness of the structure (again, like a tuning fork) not the

control surface.  The reason for balancing controls is to minimize their

impact in increasing and/or maintaining the disturbing forces. Even a

wing without ailerons or flaps (a helicopter rotor blade for example)

can flutter.  My first job was rotor blade design - I've seen wind

tunnel videos of it happening.  

If you've never seen the bridge video mentioned in Ken's article - find

it and take a look. The Kruger article is accurate.



Dennis Glaeser

BSAE - building an RV-7A



------------------------------------------------------------------------

From:		Wheeler North

I also don't entirely agree with the Kruger article.



Flutter is not a function of velocity directly, it is a function of 

force acting upon the components which may flutter. While the air 

molecules are going by at a faster rate there are far less of them so 

the resultant force doesn't nearly increase at the rate TAS does with 

gains in altitude.



Flutter is properly called negative dynamic stability and it requires 

positive static stability to occur. Positive static force pushes the 

control back to its neutral condition. When it's coupled to inertia and 

the resultant forces are able to move the control beyond that to a 

position greater then the original upset than that is negative dynamic 

stability AKA flutter. Mass aft of the pivot line adds to the inertia, 

mass at or just fwd of it takes away from the inertia. However it is 

force that causes the initial positive static desire to return to 

neutral and beyond. And it doesn't change too much with changes in 

altitude. If it did you would be able to notice it in the feel of the 

stick as altitude changed.



This is one of the primary reasons we use VNE and all the other numbers 

in indicated units. 



W

jconnell(at)rconnect.com
Guest

Posted: Mon Mar 26, 2007 7:00 am Post subject: TAS and Vne

Interesting comments on TAS, Vne, and flutter

  

 Years ago when I was flying rescue helicopters for the Air  Force,

 a B-47 pilot and I had a discussion about TAS, Vne, and  flutter.

  

 A B-47 could operate high enough that the stall speed would  

 approach Vne.  Too slow, the plane would stall -- too  fast, the

 plane would exceed Vne.  If the B-47 stalled, it would  exceed

 Vne in recovery.  The phenomena was called the "Coffin  Corner..."

    [quote][b]

LessDragProd(at)aol.com
Guest

Posted: Mon Mar 26, 2007 7:40 am Post subject: TAS and VNE

Hi All,

  

 IMHO, the purposed of the RVator (and the same article in Kitplanes)  is to keep builder/pilots of RV's from killing themselves.  Apparently  there are a number of RV-10's being built with engine installations that caused  this to be a very real concern to Van's Aircraft.

   

 My thoughts:

  

  There is no "design" flutter speed.

  



 I have heard that the RV airframe structure is the least likely to  flutter first, because of its structural stiffness.  It is expected  that the flight control surfaces would flutter first.

 Inherent in this statement is the assumption that the airframe is built to  the design documentation.

  

 The flutter speed of the flight controls is dependent on the control  system stiffness and rigging.  Where loose fitting flight control surfaces  and control attachments will flutter at a lower airspeed.   Inherent in this statement, the manufacturer of the  aircraft builds in a unique flutter speed for that airframe.

  

 The RVator (and Kitplanes) article does seem like a better way to  provide a warning about Vne and flutter speed, than to provide a fixed  number for a flutter speed that could lead to someone's  death.



  

 What I didn't like about the RVator article is the misleading statement Vne  being a TAS.

 Part 23 defines Vne as an Equivalent Airspeed (EAS).  This is a  calibrated and corrected Indicated Airspeed.  If an aircraft is NOT  designed to Part 23, I suppose Vne could be defined anyway they want.   

  

 Actually, an awareness of TAS is a very good thing.  Especially with  the GPS readout of your ground speed.  On a cruise climb in the direction  of your destination, you can monitor the TAS and the GPS ground speed.  The  difference being your headwind, or tailwind.  During your climb to  your preferred cruise altitude, you can calculate the actual headwind, or  tailwind, at the different altitudes.  If you get to your preferred cruise  altitude and find you have a greater headwind, or a lesser tailwind, than a  lower altitude, you could decide to descend back down to a more favorable  altitude. 

  

 Jim Ayers

 RV-3 sn 50

 33 years of learning about RV's 

 PS Van used to recommend that the RV-3 be flutter tested to 10% over Vne at  10,000' or higher.  Vne being stated as an IAS!  Some things do  change.  

  

 In a message dated 03/26/2007 6:41:28 AM Pacific Standard Time,  dennis.glaeser(at)eds.com writes:

  	  Quote: 	
		  -->    RV-List message posted by: "Glaeser, Dennis A"    <dennis.glaeser(at)eds.com>



I must respectfully disagree.     Flutter and dynamic stability are vastly

different things.  Flutter is    NOT the trailing edge of a control surface

flapping in the breeze like a    flag in high wind.  Flutter is the some

portion of an airframe (wing,    tail, fuselage) acting like a rubber band

due to forces in resonance with    one or more of it's natural frequencies.

Since it is a frequency, not    force, related phenomenon, that is why TAS

is key instead of IAS.  At    the right frequency, it only takes a small

force to start the process    (think tuning fork).

The force that reacts to bring the airframe back after    a disturbance is

the stiffness of the structure (again, like a tuning fork)    not the

control surface.  The reason for balancing controls is to    minimize their

impact in increasing and/or maintaining the disturbing    forces. Even a

wing without ailerons or flaps (a helicopter rotor blade for    example)

can flutter.  My first job was rotor blade design - I've seen    wind

tunnel videos of it happening.  

If you've never seen the    bridge video mentioned in Ken's article - find

it and take a look. The    Kruger article is accurate.



Dennis Glaeser

BSAE - building an    RV-7A

	


 

  



AOL now offersle="http://www.aol.com?ncid=AOLAOF00020000000339" href="http://www.aol.com?ncid=AOLAOF00020000000339" target="_blank">AOL.com. 

  [quote][b]

3edcft6(at)cox.net
Guest

Posted: Tue Mar 27, 2007 12:25 am Post subject: TAS and VNE

LessDragProd(at)aol.com wrote:

 	  Quote: 	
		   What I didn't like about the RVator article is the misleading 

 statement Vne being a TAS.

 Part 23 defines Vne as an Equivalent Airspeed (EAS).  This is a 

 calibrated and corrected Indicated Airspeed.  If an aircraft is NOT 

 designed to Part 23, I suppose Vne could be defined anyway they want.  


	


I can't see anything misleading about it.  The article clearly states 

that Fluter is a function of TAS, and therefor Vne should also be a TAS 

number.  The article then went on to offer a very plausible explanation 

on why part 23 didn't use TAS for Vne.  Further the article gave 

empirical evidence as to the fact the TAS, and not IAS or CAS, is the 

value that is critical to flutter.  So what is misleading?



-- 

Chris W

KE5GIX



"Protect your digital freedom and privacy, eliminate DRM, 

learn more at http://www.defectivebydesign.org/what_is_drm"

rtitsworth

Joined: 16 Jan 2006
Posts: 76
Location: Detroit, Mi

Posted: Tue Mar 27, 2007 5:49 am Post subject: TAS and VNE

What can be misleading is "assuming" that critical flutter speed (TAS based)

is quantitatively related to a published Vne speed.



Vne could be based on a structural deformation safety margin (dynamic

pressure / IAS related).  The critical flutter speed for a given aircraft

design could be much higher (some are, some aren't).  It's a design

parameter that is typically related to the intended operating altitude

(envelope).



Without "knowing" your critical flutter speed (TAS based), you're at a loss

for really understanding your operating envelope.  The safe/conservative

assumption then is that TAS must remain below the published Vne.



However, TAS only = IAS at STP (sea level).  At every altitude above that,

TAS is > IAS (approx 15% per 10k ft).  Thus, if you assume that TAS must

remain below Vne, then your IAS must remain below Vne at ANY altitude

(unless you're in the pattern at death valley).  That may be more

conservative than necessary (depending on the aircraft).  It also implies

that the pilot must continuously convert IAS to TAS (EFIS, E6B, placard

chart, or SWAG).



The real key is "knowing" the critical flutter speed (TAS) versus "guessing"

it's the same (or near) the published Vne.

--

lessdragprod(at)aol.com
Guest

Posted: Tue Mar 27, 2007 7:25 am Post subject: TAS and VNE

Nicely stated.

    

   Jim Ayers

    

  

 --

renewhall2

Joined: 22 Mar 2007
Posts: 7
Location: Boulder, CO

Posted: Wed Mar 28, 2007 7:34 am Post subject: Re: TAS and VNE

If flutter is based on TAS, how does Spaceshipone go supersonic with a Vne of 195kts?  I recall from the Discovery documentary, Rutan said Vne is based on IAS.  See excerpt below:

"With both engines running (800 lb thrust total) and maximum propellant load, takeoff roll is 500m (1650 ft) for 20 seconds. After pulling up, climb is established at constant airspeed at Vne, or 195 knots. Burnout is, after a maximum of two minutes, still at 195 knots indicated, which equals Mach 0.4. The maximum altitude that can be attained is 1.91 miles (10,000 ft). The maximum climb rate is 52 m/sec (10,000 ft/min). It is likely we will never take the plane to the maximum altitude capability.  None of the operating limitations of a standard Long-EZ are exceeded in this airplane, although a steep climb is needed to keep from exceeding Vne with both engines running."



From:

http://www.xcor.com/products/vehicles/ez-rocket_faq.html#performance

_________________
Bob Newhall
N829RV
RV Transition Training
Raleigh, NC
renewhall2.googlepages.com

jerry-hansen(at)cox.net
Guest

Posted: Wed Mar 28, 2007 8:09 am Post subject: TAS and VNE

That was a Long-EZ with two small rocket engines, not SpaceShipOne.



Do not archive



--

Tim Olson

Joined: 25 Jan 2007
Posts: 2879

Posted: Wed Mar 28, 2007 8:30 am Post subject: TAS and VNE

You're mistaking SpaceShipOne for the EZ-Rocket.  They're

two totally different things.



Tim Olson - RV-10 N104CD - Flying

do not archive

renewhall2 wrote:

 	  Quote: 	
		   

 

 If flutter is based on TAS, how does Spaceshipone go supersonic with

 a Vne of 195kts?  I recall from the Discovery documentary, Rutan said

 Vne is based on IAS.  See excerpt below:

 

 

 "With both engines running (800 lb thrust total) and maximum

 propellant load, takeoff roll is 500m (1650 ft) for 20 seconds. After

 pulling up, climb is established at constant airspeed at Vne, or 195

 knots. Burnout is, after a maximum of two minutes, still at 195 knots

 indicated, which equals Mach 0.4. The maximum altitude that can be

 attained is 1.91 miles (10,000 ft). The maximum climb rate is 52

 m/sec (10,000 ft/min). It is likely we will never take the plane to

 the maximum altitude capability.  None of the operating limitations

 of a standard Long-EZ are exceeded in this airplane, although a steep

 climb is needed to keep from exceeding Vne with both engines

 running."

 

 From: 

 http://www.xcor.com/products/vehicles/ez-rocket_faq.html#performance

 

 -------- Bob Newhall N829RV RV Transition Training Boulder, CO 

 renewhall2.googlepages.com

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=103428#103428

 

 

 

 

 

 

 

 http://www.matronics.com/Navigator?RV-List

khorton01(at)rogers.com
Guest

Posted: Wed Mar 28, 2007 8:51 am Post subject: TAS and VNE

As the speed increases, there are many possible bad things that can  

occur.  Examples:



flutter,

windscreen loads (either from air loads, or requirements to withstand  

bird strike by a certain weight bird),

wing structural divergence (usually only an issue on aircraft with  

forward swept wings, such as HFB-320),

flight control hinge moments become too high for acceptable control,

engine or propeller anomalies (e.g. F-104 max allowable speed was  

limited by engine compressor inlet temperature, which increased as  

Mach increased),

aircraft static or dynamic stability (e.g. Global Express max  

allowable speed at high limited by degradation in lateral stability)



Each of these bad things will have its own envelope of airspeed,  

altitude, temperature, etc that you must remain clear of.  The  

aircraft designer will specify a VNE that remains clear of all these  

bad things.



Kevin Horton



On 28 Mar 2007, at 11:34, renewhall2 wrote:



 	  Quote: 	
		   



 If flutter is based on TAS, how does Spaceshipone go supersonic  

 with a Vne of 195kts?  I recall from the Discovery documentary,  

 Rutan said Vne is based on IAS.  See excerpt below:

 "With both engines running (800 lb thrust total) and maximum  

 propellant load, takeoff roll is 500m (1650 ft) for 20 seconds.  

 After pulling up, climb is established at constant airspeed at Vne,  

 or 195 knots. Burnout is, after a maximum of two minutes, still at  

 195 knots indicated, which equals Mach 0.4. The maximum altitude  

 that can be attained is 1.91 miles (10,000 ft). The maximum climb  

 rate is 52 m/sec (10,000 ft/min). It is likely we will never take  

 the plane to the maximum altitude capability.  None of the  

 operating limitations of a standard Long-EZ are exceeded in this  

 airplane, although a steep climb is needed to keep from exceeding  

 Vne with both engines running."



 From:

 http://www.xcor.com/products/vehicles/ez-rocket_faq.html#performance



 --------

 Bob Newhall

 N829RV

 RV Transition Training

 Boulder, CO

 renewhall2.googlepages.com

rv7(at)b4.ca
Guest

Posted: Wed Mar 28, 2007 9:09 am Post subject: TAS and VNE

On 9:50 2007-03-28 Kevin Horton <khorton01(at)rogers.com> wrote:

 	  Quote: 	
		   Each of these bad things will have its own envelope of airspeed,

 altitude, temperature, etc that you must remain clear of.  The

 aircraft designer will specify a VNE that remains clear of all these

 bad things.


	


You forgot to add... That Vne will be expressed as an INDICATED airspeed.



-Rob

n5lp(at)warpdriveonline.c
Guest

Posted: Wed Mar 28, 2007 10:59 am Post subject: TAS and VNE

On Mar 28, 2007, at 11:18 AM, Rob Prior wrote:

 	  Quote: 	

 On 9:50 2007-03-28 Kevin Horton <khorton01(at)rogers.com> wrote:

> Each of these bad things will have its own envelope of airspeed,

> altitude, temperature, etc that you must remain clear of.  The

> aircraft designer will specify a VNE that remains clear of all these

> bad things.

 You forgot to add... That Vne will be expressed as an INDICATED  

 airspeed.

 -Rob

Maybe, but not necessarily a constant IAS. I have a PW-5 glider where  

VNE is expressed as a fixed figure in IAS up to a certain altitude.   

Above that altitude there is a table indicating what the different  

VNE is in IAS at that altitude.

Larry Pardue

khorton01(at)rogers.com
Guest

Posted: Wed Mar 28, 2007 12:53 pm Post subject: TAS and VNE

On 28 Mar 2007, at 13:18, Rob Prior wrote:

 	  Quote: 	

 On 9:50 2007-03-28 Kevin Horton <khorton01(at)rogers.com> wrote:

> Each of these bad things will have its own envelope of airspeed,

> altitude, temperature, etc that you must remain clear of.  The

> aircraft designer will specify a VNE that remains clear of all these

> bad things.

 You forgot to add... That Vne will be expressed as an INDICATED  

 airspeed.

Not necessarily, but it should be expressed in some way such that the  

pilot has an indicator in the cockpit that he can use to comply with  

the limitation.  Yes, in type certificated aircraft the only  

indicator that the pilot has is an airspeed indicator, that reads in  

IAS.  Some other aircraft have max allowable speeds that are  

expressed as indicated mach number at high altitudes.  The SR-71 has  

a max allowable speed that is expressed as EAS.

There is no point in providing a limitation if the pilot has no means  

at his disposal to comply with the limitation.  The last time I  

checked Van didn't require that RVs be equipped with air data  

computers that provide a true airspeed indication.  I have no idea  

how Van's expects pilots to comply with a VNE in TAS.

Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

seiders(at)bellsouth.net
Guest

Posted: Wed Mar 28, 2007 3:51 pm Post subject: TAS and VNE

Kevin, my 6A is equipped with an airspeed indicator that has ability 

to determine TAS by setting the temp/alt in window provided. I 

purchased it from Van's when building my RV.

Dick

At 04:52 PM 3/28/2007, you wrote:

 	  Quote: 	

On 28 Mar 2007, at 13:18, Rob Prior wrote:

>

>

>On 9:50 2007-03-28 Kevin Horton <khorton01(at)rogers.com> wrote:

>>Each of these bad things will have its own envelope of airspeed,

>>altitude, temperature, etc that you must remain clear of.  The

>>aircraft designer will specify a VNE that remains clear of all these

>>bad things.

>

>You forgot to add... That Vne will be expressed as an INDICATED

>airspeed.

Not necessarily, but it should be expressed in some way such that the

pilot has an indicator in the cockpit that he can use to comply with

the limitation.  Yes, in type certificated aircraft the only

indicator that the pilot has is an airspeed indicator, that reads in

IAS.  Some other aircraft have max allowable speeds that are

expressed as indicated mach number at high altitudes.  The SR-71 has

a max allowable speed that is expressed as EAS.

There is no point in providing a limitation if the pilot has no means

at his disposal to comply with the limitation.  The last time I

checked Van didn't require that RVs be equipped with air data

computers that provide a true airspeed indication.  I have no idea

how Van's expects pilots to comply with a VNE in TAS.

Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

khorton01(at)rogers.com
Guest

Posted: Wed Mar 28, 2007 4:57 pm Post subject: TAS and VNE

Is the red line on the Vans-supplied ASI on the IAS scale, or the TAS  

scale?



Kevin



On 28 Mar 2007, at 19:47, Richard Seiders wrote:



 	  Quote: 	
		   



 Kevin, my 6A is equipped with an airspeed indicator that has  

 ability to determine TAS by setting the temp/alt in window  

 provided. I purchased it from Van's when building my RV.

 Dick

 At 04:52 PM 3/28/2007, you wrote:



> 

>

> On 28 Mar 2007, at 13:18, Rob Prior wrote:

>

>> 

>>

>> On 9:50 2007-03-28 Kevin Horton <khorton01(at)rogers.com> wrote:

>>> Each of these bad things will have its own envelope of airspeed,

>>> altitude, temperature, etc that you must remain clear of.  The

>>> aircraft designer will specify a VNE that remains clear of all  

>>> these

>>> bad things.

>>

>> You forgot to add... That Vne will be expressed as an INDICATED

>> airspeed.

>

> Not necessarily, but it should be expressed in some way such that the

> pilot has an indicator in the cockpit that he can use to comply with

> the limitation.  Yes, in type certificated aircraft the only

> indicator that the pilot has is an airspeed indicator, that reads in

> IAS.  Some other aircraft have max allowable speeds that are

> expressed as indicated mach number at high altitudes.  The SR-71 has

> a max allowable speed that is expressed as EAS.

>

> There is no point in providing a limitation if the pilot has no means

> at his disposal to comply with the limitation.  The last time I

> checked Van didn't require that RVs be equipped with air data

> computers that provide a true airspeed indication.  I have no idea

> how Van's expects pilots to comply with a VNE in TAS.

>

> Kevin Horton         RV-8 (finishing kit)

> Ottawa, Canada

> http://www.kilohotel.com/rv8

aerobubba(at)earthlink.ne
Guest

Posted: Thu Mar 29, 2007 8:03 am Post subject: TAS and VNE

Hi Rob et al-

While it's true that Vne is published in IAS, there are some mitigators

that we need to keep in mind.  First, the roots of the certification rules

go back to a simpler time.  This leads to an airspeed indicator, not a TAS

indicator, being req'd to be installed by the regs and V speeds being IAS. 

These speeds are guaranteed accurate only when operating at SL and ISA. 

Some speeds, such as indicated stall speeds, by their nature continue to be

accurate with a change in altitude.  However, that particular data point

has nothing to do with the certification process.  Likewise, the fact that

many of us can read TAS directly off of our panels has nothing to do with

the process or intent of determining Vne. 

Another point is that our planes might just have a flutter onset speed in

the many hundreds of knots.  It could well be that at any max altitude an

RV might reasonably be expected to operate, the flutter margin decreases

from 200 to 100 knots.  Then again, high alt ops at published indicated Vne

could make the margin negative.  We just don't know, although the Flyin'

Tiger would lead me to suspect that this is never going to be a real

concern for a properly built and maintained RV.

To make an extreme illustration, if we were to operate an RV-8 at it's

published Vne of 200 KIAS in a standard atmosphere at, say, 67,000 feet

(Plz don't ask how we got there- it's still in development...) we would be

at the published Vne limit.  We would also be slightly in excess of Mach 1.

Now, I don't have any personal experience to draw upon here, but I'm

guessing something bad would happen to the plane and, by extension, it's

occupants.  Clearly, operating at Vne at SL is okay, so there is going to

be some transition altitude where it ceases to be okay.

The most important point to be taken from all this is that we don't know

what the limiting factor is under any given set of conditions, only that

Van's has published a value for Vne at SL ISA.  It is logical to assume

that there is a good pad built into that number, but we have no idea what

that pad is, what the "real" Vne could be, or how it is affected by

conditions.  Hence, anyone exceeding those published limits is truly

playing test pilot and should proceed with proper respect for the potential

outcome.

FWIW-  

 	  Quote: 	
		  On 9:50 2007-03-28 Kevin Horton <khorton01(at)rogers.com> wrote:

> Each of these bad things will have its own envelope of airspeed,

> altitude, temperature, etc that you must remain clear of. The

> aircraft designer will specify a VNE that remains clear of all these

> bad things.

You forgot to add... That Vne will be expressed as an INDICATED airspeed.

-Rob

glen matejcek

aerobubba(at)earthlink.net

ekells(at)sympatico.ca
Guest

Posted: Thu Mar 29, 2007 8:33 am Post subject: TAS and VNE

Kevin & the List:    Please note Van's ASI has the RED line on the IAS scale 

(doesn't move).



I have the Vans-supplied ASI. The fixed face shows Knots and Miles. The 

instrument has an adjusting knob which rotates a "disk" behind the face. 

The window at the top of the disk has a scale which rotates. This causes the 

window at the bottom of the disk to offset the fixed speed scale on the 

face.  SO, you would adjust the top window to align the altitude factor (5 

for 5,000) opposite the fixed scale for temperature (+30 to -30).  Look at 

the needle  - the fixed "black" scale shows IAS, the "white" disk shows TAS. 

Spoken without my plane here so I burned some brain cells trying to think 

this through.



---

seiders(at)bellsouth.net
Guest

Posted: Thu Mar 29, 2007 2:32 pm Post subject: TAS and VNE

It's on the IAS scale. That is the indicator I am  using most of the 

time. I use the TAS scale only when flying at or above 4000msl.

Dick

At 08:56 PM 3/28/2007, you wrote:



 	  Quote: 	
		  



Is the red line on the Vans-supplied ASI on the IAS scale, or the TAS

scale?



Kevin



On 28 Mar 2007, at 19:47, Richard Seiders wrote:



>

>

>Kevin, my 6A is equipped with an airspeed indicator that has

>ability to determine TAS by setting the temp/alt in window

>provided. I purchased it from Van's when building my RV.

>Dick

>At 04:52 PM 3/28/2007, you wrote:

>

>>

>>

>>On 28 Mar 2007, at 13:18, Rob Prior wrote:

>>

>>>

>>>

>>>On 9:50 2007-03-28 Kevin Horton <khorton01(at)rogers.com> wrote:

>>>>Each of these bad things will have its own envelope of airspeed,

>>>>altitude, temperature, etc that you must remain clear of.  The

>>>>aircraft designer will specify a VNE that remains clear of all

>>>>these

>>>>bad things.

>>>

>>>You forgot to add... That Vne will be expressed as an INDICATED

>>>airspeed.

>>

>>Not necessarily, but it should be expressed in some way such that the

>>pilot has an indicator in the cockpit that he can use to comply with

>>the limitation.  Yes, in type certificated aircraft the only

>>indicator that the pilot has is an airspeed indicator, that reads in

>>IAS.  Some other aircraft have max allowable speeds that are

>>expressed as indicated mach number at high altitudes.  The SR-71 has

>>a max allowable speed that is expressed as EAS.

>>

>>There is no point in providing a limitation if the pilot has no means

>>at his disposal to comply with the limitation.  The last time I

>>checked Van didn't require that RVs be equipped with air data

>>computers that provide a true airspeed indication.  I have no idea

>>how Van's expects pilots to comply with a VNE in TAS.

>>

>>Kevin Horton         RV-8 (finishing kit)

>>Ottawa, Canada

>>http://www.kilohotel.com/rv8

>>

aerokinetic(at)sbcglobal.
Guest

Posted: Fri Mar 30, 2007 4:47 am Post subject: TAS and Vne

 	  Quote: 	
		  >>>I was told that the MU-2 has an airspeed indicator that shows  the critical 

      airspeed for that flight altitude.  The critical airspeed is  shown as a moving
	


      (red?) line on the IAS indicator.

<<<

   

  Ain't just the MU-2... as also stated by another lister, ALL jets I know of, and most of the faster turboprops have the Vne marking on the airspeed indicator expressed as a *moving needle* (that the airspeed needle can still pass over -don't ask me how I know)  commonly called a 'barber pole', because it's typically painted red and white like, well... a barber pole.   It changes position with altitude/air density to reflect the Vne (indicated) at the present situation.

   

  Just for an example...

   

  Yesterday, like most days I fly it, I was sitting in the  Gulfstream at altitude seeing the airspeed 'bumping the pole' as they say, at M.80 ( i.e. we were *at* Vne) and the indicated airspeed (and the barber pole) was somewhere in the lower 200's. Our true was around 430 knots or so according to the ADC. We were at FL390 as I recall...  sounds about right anyway.

   

  If we had gone higher or lower the numbers would have been different... to an absolute limitation for this aircraft (GIIB) of M.85 at high altitude or 367 KCAS at low altitude. That's why the need for a 'moving redline'/barber pole

   

  So you can tell all your friends that the Vne on a Gulfstream bizjet is at around 230KIAS (give or take) in cruise flight... and blow their minds... but of course that number only applies at around 40,000 feet or so... on certain days. Some restrictions apply. Void where prohibited.

   

  And yes, flutter is real. And  it's an aero-elasticity/natural-frequency sort of thing as stated by some already... and it can kill you as stated by many. And Vans knows what they are talking about.

   

  Scott

  N4ZW

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