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11-18-2018, 04:33 AM
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Join Date: Feb 2018
Location: Ramona, CA
Posts: 175
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Quote:
Originally Posted by DanH
Or it could be as simple as a bird strike penetrating the canopy, with pilot incapacitation, followed by an overspeed event.
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The above does seem to be a likely explanation. Just a pilot reaction to a bird strike and overstress probably would not take the canopy off however an overspeed event might cause a damaged canopy to depart.
From bird strike report:
quote "Birds struck the vertical stabilizer causing it to swing top end to the left side of the
aircraft which in turn caused the bottom rod end bearing to break, which showed signs of
corrosion(post-crash). The rudder bell crank snapped near both rudder cable fittings right
side had signs of 45 degree shearing marks and left side showed signs of peeling away down
and to the left which is consistent with the vertical being struck by and object from the
left side."
I doubt pigeon strike/strikes would cause the VS to depart but the canopy definitely would.
Quote: "The FAA National Wildlife Strike Database (1990-2015) includes 20 birdstrikes with Rock
Pigeon at or above 2000 feet AGL; five of those strikes occurred between 4,000 and 6,000 feet
AGL"
I had no idea pigeons would be flying at 4,000 to 6,000 AGL.
__________________
RV-7 builder Ramona, CA.
Free prop balancing for Vans owners
(I am not in the business of prop balancing, just as a courtesy to meet other owners.)
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11-18-2018, 06:09 AM
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Join Date: May 2012
Location: Ga
Posts: 662
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Another option
Another option is to put a -8 rudder on the -7. More than one person has gone that route for looks and in my opinion, more margin.
Quote:
Originally Posted by BillL
Not hinting at this as a root cause, Jon. But to be clear, there have been 4 structural failures, all 7's, so 4 out of 1600. They are C-GNDY - overspeed, N174BK- overspeed, N307AB - turbulence, and an unfinished report for the NZ one in Jan-2018.
Regardless, the rudders all were the standard 9/7 tall rudder and seem to fail in the three pieces. This is not implying the rudder is the root cause here as it clearly is not, but it did (fact) become part of the cascade of events. I can only assume that operating the 7 within the design envelope will not result in any failures and, therefore, shall continue to own and fly my 7. Flight data is recorded for every flight.
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__________________
Craig
RV-3 Sold
RV-4 Sold
RV-6a Sold
RV-9 IO-360 CS, Built and Flying
Aerostar 600A, Family Hotrod
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11-18-2018, 06:18 AM
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Join Date: Dec 2015
Location: Auburn, AL
Posts: 200
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Are the -8 and -7 rudders the same size? In other words, will the -8 rudder fit on a -7 without any modifications?
__________________
Steve T.
CFII/MEI/ATP 737,DC-10
RV-7 slow build
AUO
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11-18-2018, 07:22 AM
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Join Date: May 2012
Location: Ga
Posts: 662
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Yes
Yes, it bolts right up. You need to replace the little fiberglass tip on the vertical. Keep in mind that the larger -7 rudder will give a little better spin recovery over the -8 rudder (1 to 1.5 turns if I recall). Given the data gathered to date, I suspect that unrecoverable spins are not on the radar like the unzipped rudders are.
Quote:
Originally Posted by RV74ME
Are the -8 and -7 rudders the same size? In other words, will the -8 rudder fit on a -7 without any modifications?
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__________________
Craig
RV-3 Sold
RV-4 Sold
RV-6a Sold
RV-9 IO-360 CS, Built and Flying
Aerostar 600A, Family Hotrod
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11-18-2018, 07:50 AM
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Join Date: Jan 2005
Location: KASH
Posts: 498
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Vans originally shipped RV-7 kits with the RV-8 rudder, then switched somewhere before 2004 because as Craig mentioned the -7's spin recovery characteristics are apparently better with the -9 rudder.
C-GNDY and N174BK were both overspeed when their failures occurred and it's reasonable to assume that this accident airplane was as well. I haven't seen any accidents like this in RV-8s, or small-tail -7s and it's also reasonable to assume that they're flying the same mission profiles - maybe even more possibility of overspeed with -8s because they're more often flown aerobatically.
Does that mean that the -7 has more overspeed margin (in either flutter or overload) with an -8 rudder? Only Van's knows the answer to that question. But in the absence of any hard engineering information I'm questioning whether to finish my -7 as-is or go back to the -8 rudder, just for the warm fuzzy of perceived margin.
I know it's legally dangerous for Van's to respond in a public forum, but perhaps they'll find another way to educate us -7 builders on this topic.
Dave
__________________
Dave Setser
RV-7 N701ED FLYING!
Nashua, NH (KASH)
Last edited by Thermos : 11-18-2018 at 08:12 AM.
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11-18-2018, 08:36 AM
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Join Date: Dec 2014
Location: Just Minutes from KBVI!
Posts: 1,039
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Quote:
Originally Posted by DanH
Or it could be as simple as a bird strike penetrating the canopy, with pilot incapacitation, followed by an overspeed event.
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Honestly, this seems like a very likely scenario, given the various reports in the docket (including a subtly veiled reference in the Smithsonian's report), but why in the world is there no discussion or photographic reference to the condition of the canopy as found?
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11-18-2018, 08:49 AM
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Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 2,791
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Quote:
Originally Posted by DanH
Or it could be as simple as a bird strike penetrating the canopy, with pilot incapacitation, followed by an overspeed event.
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seems unlikely with two pilots aboard.
__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 800+ for all
Simplicity is the art in design.
My Artwork is freely given and published and cannot be patented.
www.rvplasticparts.com
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11-18-2018, 09:54 AM
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Join Date: May 2010
Location: Baton Rouge, La.
Posts: 753
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Please excuse my ignorance and a bit of a thread drift, but would someone please describe in a little more clear concise way the differences in the 7 and 8 rudder? It would also be helpful if someone could maybe post a picture or two of the differences and or a link that details the differences. I'm about to start building the rudder for my -7 and if there's really a benefit to going with the 8 rudder, then now's the time for me to make that change.
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11-18-2018, 10:54 AM
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Join Date: Dec 2015
Location: Auburn, AL
Posts: 200
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Quote:
Originally Posted by Thermos
But in the absence of any hard engineering information I'm questioning whether to finish my -7 as-is or go back to the -8 rudder, just for the warm fuzzy of perceived margin.
Dave
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I was thinking the same thing Dave.
__________________
Steve T.
CFII/MEI/ATP 737,DC-10
RV-7 slow build
AUO
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11-18-2018, 11:24 AM
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been here awhile
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,301
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Quote:
Originally Posted by Mark33
Please excuse my ignorance and a bit of a thread drift, but would someone please describe in a little more clear concise way the differences in the 7 and 8 rudder? It would also be helpful if someone could maybe post a picture or two of the differences and or a link that details the differences. I'm about to start building the rudder for my -7 and if there's really a benefit to going with the 8 rudder, then now's the time for me to make that change.
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Moderator note;
This line of inquiry needs to be in a separate thread. Please move the RV-X tail discussion to its own thread so the discussion of this tragic accident can proceed uninterrupted.
Thanks
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