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Vne dependent on TAS?
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tedd(at)vansairforce.org
Guest

Posted: Mon Mar 26, 2007 3:31 pm Post subject: Vne dependent on TAS?

 	  Quote: 	
		   BTW, is there a term for exceeding Vne, sort of like the Mach

 number?


	


Breaking the flutter barrier?



do not archive

Terry Watson

Joined: 09 Jan 2006
Posts: 290
Location: Seattle, WA USA

Posted: Mon Mar 26, 2007 4:43 pm Post subject: Vne dependent on TAS?

Ted, somehow that doesn't seem quite macho enough. 






 	  Quote: 	
		   BTW, is there a term for exceeding Vne, sort of like the Mach

 number?


	


Breaking the flutter barrier?



do not archive

Neal.George(at)hurlburt.a
Guest

Posted: Tue Mar 27, 2007 5:09 am Post subject: Vne dependent on TAS?

Vp maybe ?  Pieces Velocity. 



Neal George

RV-7 N8ZG

Cowling






Ted, somehow that doesn't seem quite macho enough. 






 	  Quote: 	
		   BTW, is there a term for exceeding Vne, sort of like the Mach number?


	


Breaking the flutter barrier?



do not archive

sportav8r(at)gmail.com
Guest

Posted: Tue Mar 27, 2007 5:54 am Post subject: Vne dependent on TAS?

Vkg: Kiss-your-airframe-Goodbye velocity



On 3/26/07, Tedd McHenry <tedd(at)vansairforce.org> wrote:

 	  Quote: 	
		   



 > BTW, is there a term for exceeding Vne, sort of like the Mach

 > number?



 Breaking the flutter barrier?



 do not archive

n801bh(at)netzero.com
Guest

Posted: Tue Mar 27, 2007 6:06 am Post subject: Vne dependent on TAS?

I am proposing flutterbye. 

When we flew our new kitplanes for the first time we all had "butterflies" in our stomach. Now, if we dare to explore the realms of flutter the results will be instantly obvious, once it starts to flutter you can say "bye bye'...    ) 

do not archive

Ben Haas

N801BH

www.haaspowerair.com



-- "George, Neal E Capt MIL USAF 605TES/TSI" <Neal.George(at)hurlburt.af.mil> wrote:

--> RV-List message posted by: "George, Neal E Capt MIL USAF 605TES/TSI" <Neal.George(at)Hurlburt.AF.MIL>



 

Vp maybe ?  Pieces Velocity. 



Neal George

RV-7 N8ZG

Cowling



--> RV-List message posted by: "Terry Watson" <terry(at)tcwatson.com>



Ted, somehow that doesn't seem quite macho enough. 



--> RV-List message posted by: Tedd McHenry <tedd(at)vansairforce.org>



 	  Quote: 	
		   BTW, is there a term for exceeding Vne, sort of like the Mach number?


	


Breaking the flutter barrier?



do not================================================     - The RV-List Email Fo;List utilities such as the Subscriptions ================================================     - NEW MATRONICS WEB FO======================================================   [quote][b]

Jekyll

Joined: 22 Feb 2006
Posts: 44

Posted: Tue Mar 27, 2007 6:26 am Post subject: Re: Vne dependent on TAS?

Don't know a term for the event but I have one for the pilot that breaches the "barrier": Flutter Nutter.



Jekyll

aerobubba(at)earthlink.ne
Guest

Posted: Tue Mar 27, 2007 4:07 pm Post subject: Vne dependent on TAS?

Hi Terry-



How's this one:  Warrantee void speed?  Or, Speed Of Imminent Destruction?



 

 	  Quote: 	
		  Ted, somehow that doesn't seem quite macho enough. 

 
	


 

 	  Quote: 	
		  > BTW, is there a term for exceeding Vne, sort of like the Mach

> number?

 
	


 	  Quote: 	
		  Breaking the flutter barrier?

 
	


 



glen matejcek

aerobubba(at)earthlink.net

cjensen(at)dts9000.com
Guest

Posted: Wed Mar 28, 2007 3:10 am Post subject: Vne dependent on TAS?

Vtp......test pilot.



Chuck Jensen

--

Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Wed Mar 28, 2007 3:52 am Post subject: Vne dependent on TAS?

How about getting to the root -  Vk (Killing velocity)



Ed Anderson

---

_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

jpleasants(at)bellsouth.n
Guest

Posted: Wed Mar 28, 2007 6:10 am Post subject: Vne dependent on TAS?

How 'bout:



    Vflu?



    Vd  (danger)  (dumb) (disintegration) ?



    Vafu  (all a'flutter) ?



Jim Pleasants



do not archieve

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Thu Mar 29, 2007 11:41 am Post subject: Vne dependent on TAS?

Small planes have a ONE SIZE (Speed) FITS ALL, Vne, since we don't fly very high our flutter margin does not change much and there is some FAT to use or cover our butts, in theory, BUT getting near or into the TEENS, watch out diving at indicated Vne speed. 

   

  As long as the flutter margin has enough FAT in it, it can handle all operational altitudes. However FLY high in any GA plane to its MAX Service ceiling, say at min weight and dive to Vne, you might be playing with fire.

   

  Larry's glider analogy is a case where at normal lower altitudes, the one Vne fits all works. IT WORKS and simplifies the pilots work load while maintaining safety. However because gliders can really fly high (in the 20's or 30's or higher) they need a correction to Vne as they climb to high altitudes, most likely for flutter margin or protection. 

    

  Some say we should have an indication all the time in our RV's. Well Jets have that. They have a moving Vne/Vmo indicator. Light planes don't fly high enough, so there is a sufficient sea level flutter margin to handle the higher altitudes it can fly, But add a turbo engine you may have a problem.

   

  IN JETS, they have a MACH / TRUE AIRSPEED indicator. The Vne is a poll actually moves in flight. Behind that moving Vne / Vmo limit is an air data computer.

   

  If you want to have one limit SPEED you would use MACH number. 

   

  M = TAS/Speed of sound = Speed of Object thru medium (TAS) / Speed of sound (in medium)

   

   

  "The speed of sound in air depends pretty much solely on the temperature of the air: the colder the air, the slower the speed of sound. Air gets steadily colder with altitude, thus the  higher you go, the slower the speed of sound. That means without going any faster, an airplane gets closer to the speed of sound as it gets higher. It's sort of like you get closer to the speed limit as you drive towards town, not because you're accelerating, but because the speed limit decreases towards your speed".

   

   

  Jets use both indicated and MACH speed indicators. At lower altitudes its indicated kts. It changes over from measuring speed in Knots to MACH at 20,000 to 25,000 feet. Above +20,000 we fly by Mach and have limits based on Mach speed. Usually in the 0.82-0.86M range. 

   

  However you can feel "high speed" buffet if you push the Vne at altitude. Buffet is not really flutter but unstable airflow over the control surfaces as it approaches supersonic speeds. 

   

  Strangely STALL SPEED (TAS) goes up with altitude. So you have to fly faster and  faster (TAS) to avoid stall! But you also have to lower your max speed due to flutter. YOU CAN SEE THEM COMING TOGETHER!  

   

  Jets fly so high they can get both High Speed Buffet and Stall at the same time!  This is called the coffin corner. Most commercial jets have Ceilings of about 39,000-45,000 feet. Some of the top of the line bizz jets have higher service ceilings. 

   

  Again Vne is a moving target as you climb FOR ALL PLANES. Like Jets, little planes lose flutter margin as they climb into less dense air, but since we rarely climb above say 18,000 feet, ONE SIZE FITS ALL.. As long as there a conservative Vne and flutter margins to cover it, a single Vne is all that is needed for most normally aspirated planes. 

   

  As was pointed out Vne is not necessarily a flutter margin, it is most likely a  structural limit. It is harder to break the plane at altitude because there is less air pressure and stall is more likely before load factor is an issue. On the other stability, control and flutter take over at altitude. If you take it to an extreme (space) at some point the wings and control surfaces do nothing.

   

  We can make our own Vne card. (Assume Vne 10 mph IAS sea level)

  At 10,000 feet TAS to indicated is about 12% (Vne 187 IAS)

  At 16,000 feet TAS to indicated is about 27%. (Vne 165 IAS)

   

  (super conservative but it works)

   

  Once you get to 10,000 feet to 12,000 feet you are starting to get into your flutter margin by flying INDICATED speed Vne.  For example diving at 210 mph at 16,000 feet gives you 262 mph, or 52 mph over Vne. 

   

  Practically speaking MOST RV'er I know fly in the 8,000-12,500 feet  range. I have some high flying O2 sucking buddies that fly in the teens, but its less common.

   

   

  <?xml:namespace prefix = mailto />Bottom line flutter is REAL and not to be messed with. In the RVator a RV-4 pilot (who also was a fighter pilot) was flying real high, say low teens, and dove to get under a cloud deck. Well his airspeed was below Vne (indicated). He felt flutter in the elevator and slowed down. When he got on the ground and calculated the TAS he was like +40 mph above Vne (TAS) I recall. He felt the elevator flutter. Thanks to a good design and strength he was able to slow and stabilize the plane. He found his planes limit. Because RV's are home made and every elevator and counter weight is different you can bet so will flutter speed be different.

    

  RV's have been turned into 260hp clip wing "Harmon Rockets" and fly 240-250 mph tas all the time. I would say GOOD for us 4-banger RV drivers, we know there is some margin since they planes are basically the same, but we EAT that margin when we climb. Once you get mid teens, WATCH IT. Harmon guys need to really watch it since they can fly higher and faster with the higher HP.

   

  A new Harmon Rocket and new pilot to flying it was lost in California recently in  turbulent conditions. It came down I recall in some pieces. You can imagine flying fast in turbulence well above what the original RV Vne might be a recipe for disaster.  



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