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  #21  
Old 09-07-2020, 10:58 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
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Quote:
Originally Posted by grubbat View Post
Bill, are we up to 7 planes now? For some reason I thought we had 3 or 4.
I was (now edited) talking about the RV models, but I think we are up to 5 lost. There is one that happened in AZ and did not get much attention, but when finally the report was available, the crash photos showed the empennage the familiar missing VS/rudder and the HS spar was failed. It had been about 12 months between events up to the NZ one, (Dean). I hope we don't see another anytime soon.
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RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”

Last edited by BillL : 09-07-2020 at 11:09 AM.
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  #22  
Old 09-07-2020, 12:17 PM
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RV8JD RV8JD is offline
 
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There was also this RV-7 that came apart in-flight on January 26, 2015 over the Hood Canal in WA state and impacted the water. Most of the wreckage and the pilot's body (last I heard) were never recovered, so the reason for the loss of control could not be determined.
https://aviation-safety.net/wikibase/wiki.php?id=173313

https://planecrashmap.com/plane/wa/N747BA/

https://www.ntsb.gov/_layouts/ntsb.a...27X15137&key=1
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RV-8, 790 Tach Hours
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- Out with the Old, In with the New
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  #23  
Old 09-08-2020, 07:40 AM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by Marc Bourget View Post
By distinguishing the folded vs. riveted trailing edge, are you making indirect reference to the Kutta Condition?
No, I was only saying that maybe the folded trailing edge is less prone to flutter, I wasn't speculating why that might be the case. I hadn't considered the Kutta condition because I had forgotten about it, to be honest... I'll have to go back and review my aero texts...
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  #24  
Old 09-08-2020, 09:00 AM
sailvi767 sailvi767 is offline
 
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Location: Charlotte NC
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I posted this a long time ago but I once took a hard look at the accidents stats. One of the interesting things I noticed was that I could not find a single incident of inflight structural failure on a RV6 despite at the time it having far more actual flight hours than other Vans models. The difference was striking compared to the RV7.
G
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  #25  
Old 09-08-2020, 09:26 AM
BillL BillL is offline
 
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Location: Central IL
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There is a difference in the mass/weight (w/o tips) and due to larger area and centroid of the respective rudders, paint (not insignificant) will aggravate the weight and movement of the CG farther from the pivot.

While these are facts, I have no idea if they are relevant to flutter, rudder failure or safety. More knowledgable people on this subject may know.

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Bill

RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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  #26  
Old 09-08-2020, 09:55 AM
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KiloFoxtrot KiloFoxtrot is offline
 
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I have basic understanding of flutter and did attend a session on flutter in one of the OSH forums years ago. I recall that improper control surface balancing can also play a role in flutter.

Can anybody comment on the proper methods for balancing Ailerons, Elevator and the Rudder after the plane is painted?

I have asked this question of builders as I walk the RV parking area and to my surprise a fair number said they did not balance the Rudder.
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  #27  
Old 09-08-2020, 12:18 PM
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Pilot135pd Pilot135pd is offline
 
Join Date: Jan 2019
Location: Vaca Moo Airport - TA37 in East TEXAS
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Quote:
Originally Posted by N184DA View Post
A call to Dynon confirmed that with the D10A, we are out of luck.
No such ability.
I don't buy that since we're talking software here. That they don't want to spend time on it because it's not economically good for them, even though it will be a lot safer for their clients? That I will agree.

Dynon says they support all of their equipment no matter how old but experience shows it not to be 100% true unless you are using a Skyview and up. Try calling or emailing for support on a D180 and I hope you aren't grounded somewhere or your hotel bill will be lengthy. You'll get better and faster support here on VAF.

It's sad to say it because I've been a Dynon cheerleader for many years but the truth is the truth.
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  #28  
Old 09-08-2020, 12:18 PM
sblack sblack is offline
 
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Quote:
Originally Posted by sailvi767 View Post
I don’t think in this case the failure was about the IAS verses TAS issue. The aircraft was 44 knots above the IAS limit and this appears to be a low altitude event. It appears to be a very large over speed. Given the usual temps in NZ the last part of the event at 1700 feet IAS and TAS were probably almost the same.
G
So in this case the TAS vs IAS issue was not relevant. This is what I suspected. Vans list IAS because that is what most cockpits display. If you make the assumption that most rvs fly below a given max altitude (say 14,000 for arguments sake) and you base the vne in ias on that altitude then you are covered. If you have people going way above, with oxygen, then you have an issue. So there is all this discussion but I am not convinced there is an issue at all depending on what assumptions were made in converting that limit TAS to IAS. I suspect that for most of us, at the altitudes we fly, we are covered. Also there is a margin between VNE and the max demonstrated flutter speed which is another reason why Vans likely didnt feel there was a need to provide a TAS envelope.

Btw, the answer to this is NOT to install a stronger rudder! None of the airframe is cleared to these higher speeds. Beef up the rudder and something else will come off. This incident was an egregious violation of the poh. Had the pilot respected the IAS limits he would have been fine.

I think, and correct me if I’m wrong, that most of us who fly around at 10k ft and below and respect the IAS numbers have nothing to worry about.
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  #29  
Old 09-08-2020, 12:42 PM
jask jask is online now
 
Join Date: Feb 2018
Location: Ramona, CA
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Default nz accident

Quote:
Originally Posted by sblack View Post
Btw, the answer to this is NOT to install a stronger rudder! None of the airframe is cleared to these higher speeds. Beef up the rudder and something else will come off. This incident was an egregious violation of the poh. Had the pilot respected the IAS limits he would have been fine.
The above is burying your head in the sand. Mistakes are made and accidents happen. You cannot prevent accidents by saying they are illegal.
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  #30  
Old 09-08-2020, 01:10 PM
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skylor skylor is online now
 
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Quote:
Originally Posted by jask View Post
The above is burying your head in the sand. Mistakes are made and accidents happen. You cannot prevent accidents by saying they are illegal.
Sorry but Scott is right.

You can’t keep adding strength to every component that fails when limits are clearly and significantly exceeded, otherwise our planes will end up too heavy to fly!

Skylor
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