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  #1  
Old 08-16-2022, 06:13 PM
RV8JD RV8JD is offline
 
Join Date: Jan 2005
Posts: 644
Default RV-7/7A In-Flight Breakup Accident Information

There was some interest in a previous thread regarding the status of the investigations into the RV-7/7A in-flight breakup accidents that have occurred.

I put together the attached spreadsheet documenting the accidents I am aware of. The spreadsheet has embedded links to the respective national safety board's investigation reports, links to the dockets where available, and links to some references.

I plan to update this spreadsheet as necessary. If there are any accidents I missed, please let me know.

Clicking on the image below will take you to the spreadsheet.



Fly safe!
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RV-8
KAWO

Last edited by RV8JD : 11-09-2022 at 08:08 PM. Reason: Added link to Final Report for RV-7A VH-XWI.
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  #2  
Old 08-16-2022, 06:55 PM
Taltruda Taltruda is offline
 
Join Date: Oct 2017
Location: Las Vegas, NV
Posts: 1,388
Default

What are you finding to be a common link? Is it the ripper rudder coming apart from possible over speeds?
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RV-8 empenage finished 10-2020

Wings Started.. 11-2020
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  #3  
Old 08-17-2022, 12:14 AM
swift12 swift12 is offline
 
Join Date: May 2021
Location: Palmerston North
Posts: 169
Default

"Aircraft pitch is approximately 30° nose-down, wings almost level. The
IAS is recorded at 244kts"

ZK DVS....it appears commonality among some accidents is overspeed. slippery aircraft flying close to VNE pointing downwards not a good mix. I flew a lancair many years ago and came to the conclusion it was awesome to roll and a lawn dart pointing downhill...its ok...but not if you screw it up. I went over VNE pulling out and eased off...luckily the surfaces did not flutter. Id like to see the rudder have a 50% margin on the speed before breakup...maybe 300 knots but perhaps thats unrealistic.

I do wonder if the "8" rudder is better in this respect being a folded trailing edge? seeing these rudders fold in the wind is a little worrying.

In this case rudder flutter caused the vertical stab to separate and one wonders if the surface was balanced well....

quote..."Van’s Aircraft has conducted stick raps and rudder pedal kicks testing to 220kts, 8 with no indication of flutter up to this airspeed. Flight at any airspeed over Vne, however, exposes the aircraft to the possibility of flutter"

I tend to think that there is somewhat of a variance in what might be experienced between different aircraft and balance of the flight controls should be of paramount importance especially after painting. You simply cannot take flutter with a grain of salt...it destroys aircraft.

So in that case..no doubt vans has done extensive testing and in the normal envelope with balanced controls we have nothing to worry about...but overspeed or overload and add flutter.....mmmm.....poor buggers.

Its a timely reminder to do two things...
1. balance your controls
2. don't fly outside the manoeuvring speeds or g loading. if you do...carefully recover....
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  #4  
Old 08-17-2022, 06:34 AM
AndrewR AndrewR is offline
 
Join Date: Jun 2017
Location: Ballarat, VIC
Posts: 71
Default

I wonder how much difference builder to builder variations in the training edge make?

It would be interesting to compare differences in the stiffness of rudders on different aircraft. It might not require much shear movement in the trailing edge before balancing becomes ineffective because the top and bottom flutter independently.

A folded trailing edge seems like it would be much stiffer.
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  #5  
Old 08-17-2022, 06:50 AM
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plehrke plehrke is offline
 
Join Date: Sep 2006
Location: Defiance, MO
Posts: 2,021
Default

Quote:
Originally Posted by AndrewR View Post

A folded trailing edge seems like it would be much stiffer.
Remember that folded rudders also tend to have a dab of RTV or proseal at the end of each stiffener to help prevent skin cracking. That will tie skin and stiffeners all together making a much more robust trailing edge.
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RV-6A - flying 1000+ hours
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There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. —MARK TWAIN
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  #6  
Old 08-17-2022, 08:37 AM
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Snowflake Snowflake is offline
 
Join Date: Oct 2009
Location: Sidney, BC, Canada
Posts: 4,377
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I have the full report on C-GNDY from the TSB. In addition to the overspeed in flight (also over 240 kt if I recall) the conclusion was that the rudder was severely unbalanced. It had been inspected in an unpainted condition, and afterwards it was painted and that included some significant (up to 1/8" thick) filler used smooth the rudder and elevator surfaces. There was no evidence that the surfaces were re-balanced after the paint job.

So in addition to keeping speeds under Vne, keep your control surfaces balanced.
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1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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  #7  
Old 08-17-2022, 08:47 AM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 6,410
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You can't blame structural failures on the airframe when it's taken over Vne and/or people are making massive control inputs at way over Va.

Step outside any of the limits and you're on your own as several pilots have sadly discovered here. Flutter and overstress are not things you can ignore and remain part of this world for long.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 460.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ



Last edited by rv6ejguy : 08-17-2022 at 01:45 PM.
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  #8  
Old 08-17-2022, 10:24 AM
Bob Martin's Avatar
Bob Martin Bob Martin is offline
 
Join Date: Jan 2005
Location: Charlottesville, Virginia
Posts: 1,322
Default

Are builders actually balancing the counterbalanced rudders?
Thought Vans said installed the kit provided lead and that was enough on the rudder...........
Wondering now..
My original -6 rudder wasn't balanced at all.
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Bob Martin
RV-6, 0-360 Hartzell C/S, Tip up, 1200+TT
James extended cowl/plenum, induction, -8VS and Rudder. TSFlightline hoses. Oregon Aero leather seats.
D100-KMD150-660-TT ADI2- AS air/oil seperator. Vetterman exhaust with turndown tips.
Louisa, Virginia KLKU N94TB
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  #9  
Old 08-17-2022, 10:53 AM
wirejock's Avatar
wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 5,731
Default Balance rudder

Quote:
Originally Posted by Bob Martin View Post
Are builders actually balancing the counterbalanced rudders?
Thought Vans said installed the kit provided lead and that was enough on the rudder...........
Wondering now..
My original -6 rudder wasn't balanced at all.
Manual doesn't mention balancing the rudder. Unless I haven't gotten that far. If memory serves, it's fairly aft heavy even with the weight. I would think it would take a bit of lead to get it balanced.
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Larry Larson
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E-mail: wirejock at yahoo dot com
Builder Blog: http://wirejockrv7a.blogspot.com
Donated 12/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #10  
Old 08-17-2022, 11:45 AM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 2,901
Default A Must Read

For anyone with limited aerobatic experience planning aerobatics in an RV, Van's An Aerobatic Epistle is a must read. That also took me to a lengthy article by Van and others that was submitted for publication in Sport Aviation. I don't know if it was ever published. "Aviation Courtesy"
The difference between the aerobatic RV's when compared to many other aerobatic aircraft is the wider range between stall and Vne, Epistle details how easy it is to impose a load of 20 G's on an RV by yanking on the stick at or near Vne.
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