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  #81  
Old 05-19-2011, 08:49 PM
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Ron Lee Ron Lee is offline
 
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10,000 - 12,000 FPM descent is not trivial when you are at 2650 feet AGL.
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  #82  
Old 05-19-2011, 08:51 PM
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Lots of speculation in this thread about the trailing edge and I think jumping to conclusions that this was a contributing cause. If the rudder failed catastrophically (as control surfaces often do in flutter) the trailing edge of course would be ripped open. Look at the pictures -- half of the rudder is missing. I would not expect that joint to remain riveted if the lower half of the rudder departed the aircraft.

You could just as easily argue (based on photos in the report) that the rudder fluttered, the counterbalance arm (which would suffer a lot of damage due to the inertia of the counterbalance weight) failed and ripped the rudder in two.

The point is the failure mode of the rudder is almost irrelevant. At 20% above Vne you are a test pilot and along for the ride.
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Last edited by Jamie : 05-20-2011 at 11:26 AM.
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  #83  
Old 05-19-2011, 09:20 PM
Kyle Boatright Kyle Boatright is offline
 
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Quote:
Originally Posted by Jamie View Post

The point is the failure mode of the rudder is almost an irrelevant. At 20% above Vne you are a test pilot and along for the ride.
Exactly. Add in the fact that this overspeed occurred during maneuvering flight and possibly in the vicinity of wake turbulence, and I don't see it as an airframe problem.

Airplanes have published limits for a reason.
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  #84  
Old 05-19-2011, 09:34 PM
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RVG8tor RVG8tor is offline
 
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Default Load kills energy

Quote:
Originally Posted by lostpilot28 View Post
Right...you guys are missing my point. I'm trying to say that 12,000 fpm descent is not in and of itself a bad thing. Even as you pointed out, at a 45-degree angle, you're still not even getting close to Vne. An earlier post mentioned the descent rate in a "holy cow!" type of tone, but I am trying to convey that those rates are not unusual. I think I passed 11,000 feet ASCENT on a loop during Phase 1 testing with an aerobatic test pilot. Entry speed of 175 mph and a 4G pull...going up the front side of that loop is a high rate, as is going down the backside.

My over-all point is that no-one should focus on that number (fpm descent), but they should be looking at the pilot's Vne.

Quick question regarding what someone should do in the event they're pointed down (let's say on the back side of a loop or a split S) and you're rapidly approaching Vne. Let's say your doing over 200 mph pointed straight down. But, as in this case, you're only pulling 3 G's. I would think that loading up your wings to 4.5 or even 5 G's would better your situation, assuming you could grunt through it without blacking out. Wouldn't you be managing your speed at the cost of increased drag?

I hope I never have to find out, but I would think the safer thing to do is pull as many G's as the airframe could take to keep your speed under control. Thoughts?

You are correct if you are going down hill fast the last thing you want to do is back off on the "G", the load is actually and energy killing maneuver. Pull but remain with in aircraft limits until nose is approaching the horizon and then zoom up until you get your speed under control

Do some level 3-4 G level turns and see how your airspeed bleeds off, it is the same in the vertical its just that you have God's "G" working for or against you.

I am surprised at the number of guys that go out and do this stuff without any training. Flying trail off another airplane is not like aerobatics, it is more complicated, doable but you need someone with experience. The lead in this case has some of the blame because he did not monitor his own energy state, a good lead knows that #2 is having to pull more and go faster or slower in some cases to stay in position.

From a safety standpoint since so many are flying formation and doing extended trail stuff, the community needs to come up with some standards, power setting, do-not-exceed parameters as lead and wing and wingmen need to know when to call "Knock it off" and break out from the formation.

I have to add that this was an exceptionally written accident report something on can learn from.

Fly smart, fly safe but most importantly have fun doing both.
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  #85  
Old 05-19-2011, 09:42 PM
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Update on the lab reports: I have submitted a request, I was hoping they could come from my contact at the TSB directly, but unfortunately it has to go through the ATI department (Access To Information) and needs approval. I'll update when I find out how that goes. Hopefully it won't take *too* long.

They did say that the reports are PDF's, but if they're too large they would have to snail mail copies. I have requested that they try emailing it even if it's big, and barring that to burn them to a CD for mailing. We'll see what happens.
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  #86  
Old 05-19-2011, 09:42 PM
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Quote:
Originally Posted by rocketbob View Post
I disagree with the findings of the report (page 11).

1. Exact balance is not required of a control surface to prevent flutter.
2. There is no evidence provided that flutter occurred.
3. Not reweighing after paint did not cause this accident.
4. Being over gross did not cause the rudder to fail.

The #1 cause of this accident was doing acro well beyond Va and Vne. This is pure speculation on my part but if they were rat racing, well beyond Vne, its easily possible that the rudder/VS failed when this aircraft entered turbulent air or the wake of another aircraft.
I totally agree with this opinion. The aircraft had over two hundred trouble free hours on it. Exceeding Vne and Va may cause ANY aircraft to breakup. I am sure we all remember the Airbus that came apart over the Atlantic. Va and Vne are not arbitrary numbers they are laws of physics. I have been worried about this accident for some time now. Reading this report gives me a large amount of relief and confidence in what I am building will be structurally sound. Having said that, I am reminded that we all make mistakes and some pay with their lives. My heart goes out to his family.
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Last edited by aarvig : 05-19-2011 at 10:02 PM.
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  #87  
Old 05-19-2011, 10:15 PM
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Quote:
Originally Posted by Ron Lee View Post
10,000 - 12,000 FPM descent is not trivial when you are at 2650 feet AGL.
Agreed, but I've done loops at 3,000 AGL and I believe those rates are typical. What I do NOT think is typical is going 40 mph over Vne. In any attitude that's bad, but especially in a descent.
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  #88  
Old 05-19-2011, 10:21 PM
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LifeofReiley LifeofReiley is offline
 
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I'm very conservative flying my 7A, but I elected to keep the 8 rudder due to my personal opinion on the design of the newer 9 rudder going on the 7, as I feel it's not really designed for the 7 craft...
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Last edited by LifeofReiley : 05-19-2011 at 11:58 PM.
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  #89  
Old 05-19-2011, 11:18 PM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by Bob Collins View Post
So I have this airplane project and the <strike>rudder</strike> elevator 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?
I would suggest to consult with VANs and other knowlagble people in this area and not leave it for chance. You also may want to wait and balance it after paint, if you are going to paint the plane. When I finished mine, after painting my elevators were on not balanced any more and after talking to Vans, they recommend to balance them as closely as possible. I end up adding about 5.5 OZ of weight to my elevator to get them fully balanced.
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  #90  
Old 05-20-2011, 12:06 AM
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LifeofReiley LifeofReiley is offline
 
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Default Sorry...

Guys and Gals,

This paint... balance is BS !!! Fly by Van's numbers and everything will be fine balanced/painted or NOT.
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