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Vne and flutter explained - Australian Flying

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peterz(at)zutrasoft.com
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Posted: Wed Oct 14, 2020 10:13 am Post subject: Vne and flutter explained - Australian Flying

I’m bringing this up yet again after seeing this fresh article, after Ivan had stood by his VNE regardless of altitude (if I understood his reply the last time this was raised).



To those flying 914’s nice and high (17,000ft ish), what redline do you use, and have you ever had any concerns with flutter? This is obviously assuming no play in the hinges, and everything being properly balanced (except the rudder of course).



Cheers and thx,

Pete

C-GNPZ & kit A239



https://www.australianflying.com.au/news/vne-and-flutter-explained?fbclid=IwAR2xubO_DrR8uHQ72ou3uc8k2nwQwSIJtGf9RsWqAyJrkD_--pW6x7_4svU

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John Wighton

Joined: 18 May 2010
Posts: 241

Posted: Thu Oct 15, 2020 12:28 am Post subject: Re: Vne and flutter explained - Australian Flying

Pete,



The article is 10 years old -a period which represents approximately 1/12 (or 8% ish) since Wright Bros made their mark.  Much can happen in a very short time, primarily due to the predictive tools we (as aeronautical engineers) have at our disposal.



Jim's excellent article does, however, still contain good information.  The key elements being that there is a significant factor between Vne and Vd (typically 1.3-1.4), and that flutter should not occur before 1.2Vd.  Hence no sane pilot should get anywhere near.  But that also assumes an aircraft is in tip-top condition.



A simple route is to always fly using IAS.  Ensure you have calibrated your ASI, hence you are effectively flying CAS.



This actually ignites a pet subject of mine - the LAA permit renewal flight test, which requires us all to be Test Pilots for the day - reaching Vne.  A little bit like cycling toward the edge of Beachy Head but (skillfully) avoiding plummeting over the edge.  We congratulate ourselves we are still alive - and then have to go and do it again next year..........

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_________________
John Wighton
Europa XS trigear G-IPOD

clivesutton

Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH

Posted: Thu Oct 15, 2020 12:56 am Post subject: Re: Vne and flutter explained - Australian Flying

Hi Peter, thanks for posting this link to an excellent article - that explains more clearly than i've ever seen anywhere, how Flutter is initiated and influenced.

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Remi Guerner

Joined: 14 Dec 2010
Posts: 284

Posted: Thu Oct 15, 2020 2:35 am Post subject: Re: Vne and flutter explained - Australian Flying

Great article on this critical subject. It would be interesting to find out how the Europa has been evaluated during flight testing of the prototypes, especially at what max altitude the Vd testing has been actually performed.

BTW it is always instructive to look at certificated aircraft manuals and see how they handle any issue. The attached page is from the Cirrus SR22T POH. It shows how they handle the VNE/flutter issue at high altitude. The VNE IAS is reduced linearly above 17500 ft. from 205 kts to 175 kts at 25000 ft. Very few Europas are operated at such high altitudes, but it may be advisable for their pilots to consider reducing their VNE as Cirrus do. 

Surprisingly Cirrus also reduce the VNO above 17500 ft: obviously this has nothing to do with flutter, so why?



Remi Guerner

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clivesutton

Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH

Posted: Thu Oct 15, 2020 2:42 am Post subject: Re: Vne and flutter explained - Australian Flying

Good points John.



RE: the LAA annual VNe dive- what is your understanding of the reasoning /logical justification behind this LAA (supported by the UK CAA), requirement?

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Duncan McFadyean

Joined: 18 Jan 2011
Posts: 219

Posted: Thu Oct 15, 2020 6:44 am Post subject: Vne and flutter explained - Australian Flying

I'm happy that my Europa is only cleared to 1300lbs MTOWA and therefore I only have to Vne-dive to 150knts, leaving the XSs to explore the class-envelope at a much higher speed!



Duncan McF

do not archive

 	  Quote: 	
		   On 15 October 2020 at 09:28 John Wighton <john(at)wighton.net> wrote:

 

 

 

 

 Pete,

 

 The article is 10 years old -a period which represents approximately 1/12 (or 8% ish) since Wright Bros made their mark.  Much can happen in a very short time, primarily due to the predictive tools we (as aeronautical engineers) have at our disposal.

 

 Jim's excellent article does, however, still contain good information.  The key elements being that there is a significant factor between Vne and Vd (typically 1.3-1.4), and that flutter should not occur before 1.2Vd.  Hence no sane pilot should get anywhere near.  But that also assumes an aircraft is in tip-top condition.

 

 A simple route is to always fly using IAS.  Ensure you have calibrated your ASI, hence you are effectively flying CAS.

 

 This actually ignites a pet subject of mine - the LAA permit renewal flight test, which requires us all to be Test Pilots for the day - reaching Vne.  A little bit like cycling toward the edge of Beachy Head but (skillfully) avoiding plummeting over the edge.  We congratulate ourselves we are still alive - and then have to go and do it again next year..........

 

 --------

 John Wighton

 Europa XS trigear G-IPOD

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=498828#498828

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