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  #1  
Old 03-20-2019, 07:22 AM
Turbo69bird Turbo69bird is offline
 
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Default Rudder flutter and added weight. Adsb tail beacon

So in reading one of the accident reports where rudder flutter was the cause and a little body filler blamed it occurred to me that the weight of something like a tail beacon ADSB solution could be a factor.
Any thoughts on rebalancing or of would cause issue would be appreciated.

I already have the old style rudder without the counter balance. Not sure how that adds to the situation.
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  #2  
Old 03-20-2019, 07:51 AM
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rv8ch rv8ch is offline
 
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Default flutter

Quote:
Originally Posted by Turbo69bird View Post
So in reading one of the accident reports where rudder flutter was the cause and a little body filler blamed it occurred to me that the weight of something like a tail beacon ADSB solution could be a factor.
Any thoughts on rebalancing or of would cause issue would be appreciated.

I already have the old style rudder without the counter balance. Not sure how that adds to the situation.
I am no aero engineer, but from what I have read about flutter any kind of change can have a positive or negative impact on flutter, and even both depending on the speed of the airflow over the surface.

The accident where the body filler contributed, there was also high speed involved.

Quote:
At the time of the vertical stabilizer and rudder separation, the aircraft was at or near 234 knots, exceeding the 200 knot Vne and the speed at which the aircraft was shown to be flutter free. The theoretical flutter onset speed was 300 knots. Adding extra weight (paint and filler) can reduce the speed at which flutter onset occurs by 50 knots or greater. It is possible that the manoeuvre overstressed the rudder, reducing its stiffness, which further lowered the flutter speed.
http://www.vansairforce.com/communit...ad.php?t=72316

http://www.vansairforce.net/safety/G-GNDY.pdf
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  #3  
Old 03-20-2019, 08:38 PM
Turbo69bird Turbo69bird is offline
 
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Default

Anyone know the rebalance
Procedure my field A&P says the way they want it done is manufacturer and mode specific.
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  #4  
Old 03-21-2019, 07:32 AM
BillL BillL is offline
 
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There are 5 RV7's that have had inflight failures, all were the tall rudder shared with the 9. All the rudder pieces looked much the same but the causes were different, as listed in the reports. Several of the HS spars were failed (maybe all but don't recall), and the VS broken.
1- Canada, 3 USA, 1 NZ.

You should call Vans for your specific situation and get an official recommendation.
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  #5  
Old 03-21-2019, 08:41 AM
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jcarne jcarne is offline
 
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Quote:
Originally Posted by BillL View Post
There are 5 RV7's that have had inflight failures, all were the tall rudder shared with the 9. All the rudder pieces looked much the same but the causes were different, as listed in the reports. Several of the HS spars were failed (maybe all but don't recall), and the VS broken.
1- Canada, 3 USA, 1 NZ.

You should call Vans for your specific situation and get an official recommendation.
It's worth noting that most if not all of them involved speeds above Vne when a tail failure was present.
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  #6  
Old 03-21-2019, 08:43 AM
von_flyer von_flyer is offline
 
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I have often wondered if this was the delay in the approval of the certified version of the "rudder trim tab" version of Uavionics ADS-b.
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  #7  
Old 03-21-2019, 08:46 AM
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DanH DanH is offline
 
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Re-balancing alone may not be an adequate compensation for added mass at the trailing edge. Control surface stiffness is also a factor, and ultimately strength. Here we're talking about adding more mass at two ends of the same structure in torsion.

As a homebuilder lacking the tools and knowledge to do a flutter analysis. I wouldn't add anything significant to the trailing edge of a surface.
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Old 03-21-2019, 09:35 AM
jask jask is offline
 
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Quote:
Originally Posted by jcarne View Post
It's worth noting that most if not all of them involved speeds above Vne when a tail failure was present.
In my case, the odds of me accidently exceeding vne during nanuvering would be much greater than accidently entering a spin. If I am dumb enough to enter a spin in a landing attempt, they aren't recoverable anyway. I am undergoing cancer treatment and if or when I resume building, I will install the early rudder.
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  #9  
Old 03-21-2019, 04:46 PM
Discus2b Discus2b is offline
 
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Get it done.
H
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  #10  
Old 03-21-2019, 05:52 PM
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azrv6 azrv6 is offline
 
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Difference in wt between Whelen tail position light (0.14 lbs) and the replacement Tailbeacon (70 grams or 0.154 lbs) is 0.014 lb.
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