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  #1  
Old 09-21-2013, 01:07 PM
Mark Burns's Avatar
Mark Burns Mark Burns is offline
 
Join Date: Jan 2005
Location: Ruston, Louisiana
Posts: 883
Default 7A elevator spar crack

Due to the recent loss of a VAF'er I decided to inspect my empennage very carefully.

I found a crack in the right elevator spar at the outboard attach point.
This is how it looked upon inspection. Just a black line.



I wiped the black off the left side but you can still see the crack below.



And here it is after the dye penetrant test.



It's an RV7A serial number 72183 with 908 hours.

Everyone please check your elevators carefully before your next flight!

Mark
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Ruston, Louisiana
RV-7A N781CM 1,700+ hrs
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A&P
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  #2  
Old 09-21-2013, 01:11 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 5,196
Default

Good catch, Mark.
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Marietta, GA
2001 RV-6 N46KB
2019? (actually 2022) RV-10 N46BX
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  #3  
Old 09-21-2013, 01:15 PM
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RickWoodall RickWoodall is offline
 
Join Date: Jan 2007
Location: Ontario Canada
Posts: 1,481
Default Interesting.

Thats a pretty signficant issue I would think. Will be interesting to see if a few of these show up, and how/why it would fracture there?

Not speculating on anything of course, but anything to do with spars gets my attention quick. Will inspect asap.

Thanks for the post.
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Rick Woodall C-GSTT "ghost"
9a -TMX io-320, catto three blade, dual dynon hdx with a/p. 1000+ hrs in 11 yrs flying.

Flew to Osh 11,12,15,17,19. SNF 2013. West to Cali /Washington/Vancouver/crossed the Rockies north to Red Deer east to Moosonee and over to maritimes. South to Jekyll Isl, cedar key, and Key West etc. 8 trips and 17 islands of the Bahamas. Flown turtles and dogs for Pilots n Paws too. Love our Rv's
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  #4  
Old 09-21-2013, 04:56 PM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 7,023
Default

A loose jam nut could be the cause of such a crack, if the jam nut is loose the nutplate and nutplate rivets are carrying the full load of the fitting.

FYI - I find loose jam nuts on elevators and rudders routinely

PS: good find, everyone should inspect this area at the earliest opportunity.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
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Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
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Last edited by Walt : 09-21-2013 at 04:58 PM.
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  #5  
Old 09-21-2013, 05:06 PM
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F1Boss F1Boss is offline
 
Join Date: Aug 2006
Location: Taylor Texas
Posts: 862
Default Whoa!

Hey Mark:

Assuming the rod end was tight, and the elev hinge line along the H stab rt side is razor straight, as is the elev hinge line, I would suspect a vibration mode of some sort here (elev counterweight involved) - I doubt you could do that with any sort of flying you would do in that plane - well - maybe 10 tail slides per day since the first flight? You're not doing that, are you?

I suspect a hinge line SNAFU, with the area of least strength (outboard hinge/smallest spar cross section)) giving up 1st. Get your dental floss and string-line bushings back out!

Could be that rivet was not driven correctly - the markings show it is a hard rivet...so that's not likely to be it.

What engine/prop combo are you running? Does it run smoothly in cruise? Did you do an engine run with the wings off way back when?? I'm digging pretty deep with that last one...

Carry on!
Mark
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  #6  
Old 09-22-2013, 06:11 AM
cajunwings cajunwings is offline
 
Join Date: Jun 2007
Location: new iberia la
Posts: 944
Default Spar Crack

Mark: Good Job for paying attention and being proactive. No way to tell how long your crack has been there but looks like a few hours. This is a good illustration of how the parts of our "airworthiness system" work together. The airplane structure is designed to be tolerant of some level of damage or defect like this spar crack for a peroid of time until the inspection process comes around to catch it. Please keep us posted on what you find and how you resolve it.



Don Broussard

RV-9 Rebuild in Progress
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  #7  
Old 09-22-2013, 06:35 AM
danP danP is offline
 
Join Date: Nov 2010
Location: Monroe, La
Posts: 39
Default

Thanks for the info Mark !
Hope to see ya soon.
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  #8  
Old 09-22-2013, 09:04 AM
g zero g zero is offline
 
Join Date: Jun 2007
Location: palm coast fl.
Posts: 1,061
Default Crack

My Cessna 120 had an AD to look for such a crack , along with the Rudder on an A36 Beech Bonanza , and the horizontal on a Rockwell 112 . I do believe the fix was either doublers or spar replacement .
As inexpensive as Vans parts go , I might opt to build a new one . A complete tail kit cost about the same as the cost to inspect the A36 or the Rockwell .
After the latest inflight breakup and another post about the length of rudder rod bearings we all need to take a realy good look at the tail components .
Remember tail kits are place that most every one learns on , most with NO construction experiance .

The latest 7 to come apart looks a lot like [ed. Wait for the investigators please. dr]. There are some other reports of RV7 flutter if you search the web.

Tom
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Last edited by DeltaRomeo : 09-22-2013 at 09:10 AM.
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  #9  
Old 09-22-2013, 11:45 AM
bruceg bruceg is offline
 
Join Date: Sep 2011
Location: AL
Posts: 69
Default Thanks

Mark, thanks for the post. I checked a friends RV-7 and found all 4 jam nuts loose on the elevator hinge rod-ends. No cracks though.
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  #10  
Old 09-22-2013, 11:45 AM
humptybump humptybump is offline
 
Join Date: Feb 2011
Location: USA
Posts: 3,166
Default

Mark - thanks for this thread.

On you're prompt, I just looked closer than usual at the lock nuts for both the rudder and elevator on my RV-8.

One of three on the rudder needed a wrench. One in four on the elevator needed a wrench.
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