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  #41  
Old 05-19-2011, 12:10 PM
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Ron Lee Ron Lee is offline
 
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I have ZERO concern after reading this.

My opinion: Gross pilot error.
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  #42  
Old 05-19-2011, 12:15 PM
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L.Adamson L.Adamson is offline
 
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Quote:
Originally Posted by Ron Lee View Post
I have ZERO concern after reading this.

My opinion: Gross pilot error.
Which translates too:

RV speeds can build up VERY fast on the downhill! So keep it in mind! Reports such as this, tragic as they are, at least remind us.

L.Adamson
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  #43  
Old 05-19-2011, 12:17 PM
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Jamie Jamie is offline
 
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Quote:
Originally Posted by RV7Guy View Post
After reading the entire report, I have to agree with RocketBob on this. There are some conclusions based on information but nothing conclusive. Since a video was running, what was shown at the moment of the first harmful event? I would think there would be some evidence on the video of a buzz, yawing etc...
The report was quite clear in this regard.

Top of page 4:

Quote:
During a pull-out from a rapid descent, there was a sudden onset of an airframe vibration
(shuddering around the longitudinal axis), which was followed by a yawing motion, a roll and
ground impact.
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  #44  
Old 05-19-2011, 12:18 PM
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JonJay JonJay is offline
 
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Default I treat VNE like it is a wall.

It seems a lot of this discussion is analyzing the report to come to some conclusion that even those that wrote the report and studied the accident where unable to come to. As some have noted in their comments, "pure speculation".

Bottom line; If you exceed VNE, in any flight condition, structural damage can occur. Throw any kind of manuevering, and certainly aerobatics, and wow, recipe for a disaster. We all believe Van's published numbers to be conservative but I dont treat them as such. I have flown to VNE in Phase I. I have ventured a bit above it a few times, usually letting down from up high, pretty easy to do on the 6 with a lower VNE. But, I treat it like if you go there, something bad WILL happen. I treat the yellow arc with the same care.

The simplest take away here is that as good as these machines are, they have limits. What those are may be up for debate, but I believe if you go beyond Van's published numbers you are taking your life into your hands. Don't put yourself in a position knowingly unless you are willing to take that risk, and if you unknowingly get into that position, fly the airplane and correct the condition.
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Last edited by JonJay : 05-19-2011 at 12:25 PM.
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  #45  
Old 05-19-2011, 12:23 PM
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JonJay JonJay is offline
 
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Default I am sure you are not alone....

Quote:
Originally Posted by Bob Collins View Post
So I have this airplane project and the rudder is not perfectly balanced. Why? Who knows why but it is aft heavy and when you add in the manual trim cable it is even more aft heavy. It's not painted, of course, but the tips are done.

Should I be cracking those emp tips open and starting over with adding more weight?
...and of the hundreds of machines flying none have failed with the few exceptions of gross over stress (a few is an assumption, perhaps only one?). As mentioned, can't balance a 6 rudder.....Might be a good poll; who has balanced their rudder? I suspect very few....
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  #46  
Old 05-19-2011, 12:28 PM
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Neal@F14 Neal@F14 is offline
 
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Quote:
Originally Posted by fl-mike View Post
Here’s my theory:
At way past Vne, the rudder counterbalance tore off, maybe due to a bit of flutter and the resulting aerodynamic load on the surface ahead of the hinge line when it got in the slipstream.
After that, things rapidly went from bad to worse.
As that happened, it overstressed the vertical stab, which broke off and ripped off the top half of the rudder, explaining the damage to the middle part of the rudder.
Otherwise, the damage to the top of the rudder makes no sense. It did not get damaged in the separation or ground impact. It had to be the initiating event.

discuss
Very interesting theory. Could just the aerodynamic load alone be enough to rip away just that top portion of the rudder? Just how strong is that part of the structure up there?
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  #47  
Old 05-19-2011, 12:29 PM
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Kahuna Kahuna is offline
 
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My free 2 cents.
The picture shown in the report reminds me of a video posted here a while back that scared me to death. I see that picture and my heart sinks. Bad geometry. Trouble pending.

Tail chasing aerobatics in the hands of a low time pilot can be disasterous.
My Theory...
Im picturing -2 going down hill, bad geometry on lead, speed of heat, heat of the moment, suddenly in the wash, pulling G or not, seeing his lead approaching quickly, panic sets in, stomping on controls, nothing happening, and wham, outta the wash, flight controls in some mis-controlled manor, tail over stresses. Game over.
Or in the wash at high speed, exits in unusual attitude, then pilot induced overstressed VS with rudder to recover.

Had he been by himself, Id have more faith in the flutter. Given where he was and what he was doing, my bets on overstress pilot induced.

I probably have about as outta balanced rudder as you could have with my -8tail and a servo and tab electric in the aft of the rudder. While ive been at his speeds. I have not done it in any kind of turbulence, wash, or G. Course my tail is not his.

Just one mans opinion
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  #48  
Old 05-19-2011, 12:40 PM
John R. Graham John R. Graham is offline
 
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Quote:
Originally Posted by RV7Guy View Post
...
Regarding filler, I would think from an aerodynamic standpoint (beyond the weight added) that smoothing the trailing edge or skin would assist in preventing flutter by smoothing the air leaving the TE. I'm not an engineer so I'm just thinking out loud.
...
I think this is like thinking that, if you smooth out all the parts of a whistle enough, that it won't make a noise when you blow it. I believe there's always enough turbulence to start the resonance of you exceed the flutter margin. If for no other reason, the empennage is running in the propwash. (I'm not an aeronautical engineer, either, though.)

- John
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  #49  
Old 05-19-2011, 12:45 PM
Christopher Murphy Christopher Murphy is offline
 
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Location: colorado
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Default rudder design

This could have been caused by simply not holding both rudder cables tight. ( and exceeding Vne) I believe it was a flutter failure.

Chris M
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  #50  
Old 05-19-2011, 01:02 PM
Bavafa Bavafa is offline
 
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Location: Sacramento, CA
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Quote:
Originally Posted by Pitts View Post
Wasn't there a recorded descent rate of over 10,000 FPM shortly before the rudder and fin separated?
I saw the same number which I can not even imagine what must have been like over 10K FPM decend.
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