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  #1  
Old 04-16-2007, 06:17 PM
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rv969wf rv969wf is offline
 
Join Date: Sep 2006
Location: Beaver, OK
Posts: 447
Default Why is the VNE less on -6 versus -7 ??????????

Can someone tell me why the RV-6 has a lower VNE than the -7??? I know the tail, wingspan, etc, etc. is different between the two, but why such a difference?

Another question: How are the Rockets, Dave Anders, Tracy Saylor, etc. and the really fast birds getting away with exceeding the VNE? Thicker skins on control surfaces??? Control surfaces balanced different??? Humm, just asking.
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Alan (AJ) Judy
Beaver, OK in NO MANS LAND
RV-6 IO360A1B6 C/S Hartz 200HP ?
Also Fly North American NAVIONs
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  #2  
Old 04-16-2007, 06:24 PM
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N788RV N788RV is offline
 
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Location: Topeka, Kansas
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Default Vne

Sorry, I don't have the answer but thought that this would be a good place to put in an inquiry. I'm getting ready to start making my POH for an RV-8 and a long time ago I found a document that showed all the speeds for all the different models. It included flap speeds, Vne, Vs ect. The only thing I can locate now is in on the Vans web site and it just shows some cruise speeds and various weights and power settings. Could someone hook me up. Thanks
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  #3  
Old 04-16-2007, 06:57 PM
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rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
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Default

Quote:
Originally Posted by rv969wf
Can someone tell me why the RV-6 has a lower VNE than the -7??? I know the tail, wingspan, etc, etc. is different between the two, but why such a difference?

Another question: How are the Rockets, Dave Anders, Tracy Saylor, etc. and the really fast birds getting away with exceeding the VNE? Thicker skins on control surfaces??? Control surfaces balanced different??? Humm, just asking.
Don't know the answer to question #1.

#2, Some are beefed up but all have been tested to these speeds. I know of several who have gone close to 10% above the stated Vne without problems and designs are tested here and then have a lower limit set usually.

If you want to engage in this area of flight testing, be aware that sliders can't be opened in flight in 6s and 7s so parachute is only of use if the whole thing disintegrates!


That part gave me the willies testing my 6A. I found out afterwards about the canopy thing and that Vne was TAS not IAS. So I was actually at about 193 knots TAS. A little knowledge is dangerous.

Wiser with age and more careful today.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 445.2 hrs. on the Hobbs,
RV10 95% built- Sold 2016
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  #4  
Old 04-16-2007, 07:12 PM
hngrflyr hngrflyr is offline
 
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Location: eugene, oregon
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Default

The RV-7's rudder is counterbalanced. The original RV-6's is not. While I don't know for sure, my guess is that it has to do with the high speed flutter dynamics of the respective rudders. On the other hand, the early Harmon Rockets did not have counterbalanced rudders and are regularly flown faster than 250 MPH apparently without flutter problems. The faster airplanes fly, the less tolerent they are of anything that is not right. Small errors in building can get big in a hurry.
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  #5  
Old 04-16-2007, 11:01 PM
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RV10Rob RV10Rob is offline
 
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Location: Woodinville, WA
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Default

Quote:
Originally Posted by N788RV
Sorry, I don't have the answer but thought that this would be a good place to put in an inquiry. I'm getting ready to start making my POH for an RV-8 and a long time ago I found a document that showed all the speeds for all the different models. It included flap speeds, Vne, Vs ect. The only thing I can locate now is in on the Vans web site and it just shows some cruise speeds and various weights and power settings. Could someone hook me up. Thanks
I had a difficult time finding it, too. I think this is it, though: http://vansaircraft.com/pdf/speeds.pdf
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  #6  
Old 04-16-2007, 11:19 PM
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flyeyes flyeyes is offline
 
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Default

Quote:
Originally Posted by N788RV
I'm getting ready to start making my POH for an RV-8 and a long time ago I found a document that showed all the speeds for all the different models. It included flap speeds, Vne, Vs ect. The only thing I can locate now is in on the Vans web site and it just shows some cruise speeds and various weights and power settings. Could someone hook me up. Thanks

You might start here.
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  #7  
Old 04-16-2007, 11:24 PM
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rv969wf rv969wf is offline
 
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Default I'm concerned about the VNE on my -6 !!!!!!

Quote:
Quote:
Originally Posted by RV10Rob
I had a difficult time finding it, too. I think this is it, though: http://vansaircraft.com/pdf/speeds.pdf
Anyone know how VANs came up with the VNE numbers???? Did VANS take each plane to a set speed in small increments and feel a buzz or what??? Have any of these RV's been wind tunnel tested to see where the flutter is?

Reason I'm asking is because I've exceeded the VNE quite a few times in level flight and I'm very concerned.

I don't want to have someone writing a story about my -6 or myself in a million pieces on this forum.
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Alan (AJ) Judy
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RV-6 IO360A1B6 C/S Hartz 200HP ?
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  #8  
Old 04-17-2007, 12:21 AM
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AlexPeterson AlexPeterson is offline
 
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Location: Maple Grove, MN
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Alan, you are correct to be worried, because our planes will flutter, the only question is at what speed. An excursion once or thrice to some speed exceeding redline does not mean it is safe; there are other variables. The only thing that can be said is that the odds go up of something bad happening as the speed goes up. I think it is true that VNE from a flutter point of view is perhaps the most difficult thing to establish in an aircraft design.

Nasa had a video of what I believe was some Piper or Beech design that they were exceeding redline on, and it was horrifying to see the slow motion video.

It is my understanding that there is usually no warning, just parts coming off.

Also, it is not just IAS that matters in this regard - TAS is a huge player as well. I believe Van had an article some years ago about why TAS is also important also. The gist is that the amount of time it takes for air to cross the elevator, for example, is important. Perhaps others will be able to point to the article.
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  #9  
Old 04-17-2007, 12:53 AM
Pirkka Pirkka is offline
 
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Kitplanes had recently article where question was whether the Vne was with CAS or IAS. Needless to say but the flutter was also covered there. Good reading for a start. But generally better have Vne way bellow flutter because it's nasty. If you want to kill yourself, there are easier ways to do it.

I read March, April and May issues but can't remember in which one this article was.
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  #10  
Old 04-17-2007, 07:25 AM
David-aviator David-aviator is offline
 
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Location: Chesterfield, Missouri
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Quote:
Originally Posted by rv6ejguy
That part gave me the willies testing my 6A. I found out afterwards about the canopy thing and that Vne was TAS not IAS. So I was actually at about 193 knots TAS. A little knowledge is dangerous.

Wiser with age and more careful today.
Same here, Ross. I took my -7A up to 220 indicated coming down from 8000' doing the VNE test. Thankfully, the airplane is slightly over built for sure.
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