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03-01-2014, 08:30 AM
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Join Date: Jan 2005
Location: St. Paul, MN.
Posts: 4,792
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AN365 in a 7A
Budd Davisson's article in this month's *Sport Aviation says AN365 nuts should not be used on control surfaces on any airplane. RVs , of course, have them all over thfe place on control surface attach points.
Wondering if I should remove them at the next annual and, if so, specifically which ones and what they should be replaced with?
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03-01-2014, 09:03 AM
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Join Date: Feb 2010
Location: GTA, Ontario
Posts: 826
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Castle nuts
Hey Bob,
I had to buy a bunch of hardware for the -8 to replace any AN365 and undrilled AN3 bolt that was attached to a moving control surface. I bought various sizes of the drilled AN3 bolts and the castle nuts with a cotter pin kit and matched the length of what was on the plans.
That's one of the requirements in Canada.
Haven't replaced them yet, but will do it before my final inspection.
Cheers,
Don
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03-01-2014, 09:09 AM
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Join Date: Dec 2011
Location: Lawrenceville, Georgia
Posts: 315
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Hey bob-
Throughout my build, I've been replacing all control system hardware with locking castle nuts & cotter pins... I'm a safety nut. Using nyloc nuts anywhere in the control system freaks me out a little. I know it's proven but it's just personal preference to replace the stock hardware...
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03-01-2014, 09:10 AM
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Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,334
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There are probably somewhere around 20 to 30 AN365's on each RV's control surfaces, times about 8,000 RV's, so maybe a quarter million of them? Good enough validation for me. As long as neither end of where they are clamped rotates with respect to the bolt/nut, they are fine. I believe this agrees with AC 43-13 as well.
__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
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03-01-2014, 09:12 AM
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Join Date: Jan 2005
Location: Twin Cities, MN
Posts: 1,565
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Between a writer and a successful and well respected airplane designer, I'll trust the well respected airplane designer when it comes to hardware selection.
No disrespect to Budd Davisson - I enjoy his articles very much.
__________________
Brad Benson, Maplewood MN.
RV-6A N164BL, Flying since Nov 2012!
If you're not making mistakes, you're probably not making anything
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03-01-2014, 09:22 AM
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Join Date: Nov 2011
Location: Pompano Beach, FL
Posts: 29
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This ought to be Good!
I haven't checked the Vans Hobb meter in a while, but aren't we up to almost 8000 flying RV's or close to it. Just checked, 8583 flying according to them. And I'll bet "almost" every one of them, mine included have AN365 lock nuts on the control surfaces group. Pushrods, bellcranks, aileron, rudder, and elevator mounting, you name it. Man that's a lot of nuts!
In that application with a known good nut, how it would ever back off and come unattached would be beyond me. I'm sure Vans or somebody smarter than me will way in on this one. I know for a fact that every time I go out to fly they are always right where I left them the last time. I check during preflight. And I know, there are nuts we cant see during preflight, mainly pushrods. But they are there every annual. So am I safe or just foot loose and fancy free?
If and when Vans issues a SB on this (doubtful), I will reevaluate. I declare those AN365 nuts good little critters for my RV. But I don't use them firewall forward due to the temperature rating.
Okay, so let's pop some popcorn and watch this movie. I know Brantel put the popcorn eatting muppet on a while back and I still chuckle when I think of him.
Fly safe fellows and ladies.
Jeff
__________________
Jeff Liebman
RV-8 SOLD
Superior IO-360 Hartzell BA Prop
Steam Gauges/AFS Engine Monitor
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03-01-2014, 10:07 AM
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Join Date: Jan 2005
Location: Woodstock, Ga
Posts: 117
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The difference is rod end bearings. On the elevator and aileron hinges, control pushrods, etc, the rod end bearing is clamped between two pieces of metal by the bolt and nut. There is no rotation around the bolt at all, only in the rod end bearing. An elastic lock nut is just fine for that location. Now, the rudder cables, brake pedals, and such do see rotation around the bolt, so a cotter pin and castle nut are appropriate.
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Rod Schneider
Ball Ground, GA
RV6/Subaru
Flying!
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03-01-2014, 10:22 AM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Perhaps it really is a larger problem than we think, but just not related to RVs?
I looked at a recently purchased Air Cam and all of the control surface hinges were AN3 bolts and self locking nuts.
However, in this case the bolts were the hinges - no rod end bearings. The plane had just had a conditional inspection (aka annual..  ..) and it was not picked up then.
I checked the plans that came with the plane and sure enough they call out for castle nuts and cotter pins.
Again, perhaps it's a large homebuilt problem, just not on our RVs.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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03-01-2014, 11:16 AM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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I haven't read Bud's article, so I don't know if the OP misinterpreted something that he said, but the bottom line is "what is standard aircraft practice"?
Just because someone well respected writes a mag. article that deviates from long standing and well documented (AC 43.13, Aircraft Standards books, etc.), does that mean everyone should should suddenly change?
It is a long term industry standard (practice) that cotter pin safetied nuts be used on any fastener that is exposed to any level of rotation (a fastener where something that can move is actually pivoting on the fastener).
In almost every example I can think of on RV's where something moves, the rotating part/assembly is pivoting on a bushing or bearing that is captured by the bolt installed with the AN365 nut (the bolt is torqued to normal value and can not be rotated). In the few instances where a bolt is used as a pivot point (fwd and aft ends of rudder cables is a good example), a castle nut and cotter pin is specified.
Tangent - In fact, I would argue that in some instances, a cotterpin safetied nut could be more dangerous than a nylock one. Keep in mind, these airplanes are for the most part built by amateurs, so it is amateur level skills that are installing the cotter pins. How hard can it be you say? It is not. But there are different techniques that can be used to make them safer.
Lets say for example you have cotter pinned bolts on the aileron hing points. They are somewhat low to the ground (particularly the inboard one). Now lets say you are at a remote grass strip and while taxiing you swing you wing through some very tall grass that catches on the legs of the cotter pin (that was installed by an amateur) and bends them open, and at some time later the cotter pin falls out. Given that there is a chance of it occuring, which kind of nut would you rather have installed, if an AN365 is "by standard practice" totally exceptable?
Now I realize that the cotter pin has two legs and they should be bent in different directions, etc., etc., but this is a real scenario. I am aware of cotter pins being lost from rudder cables on tail draggers that regularly get run through tall grass, or on rudder pedals from peoples shoes, because the bolt wasn't oriented to prevent shoe contact.
My main point is "do not become complacent and assume that just because an AN365 nut has been replaced and is now safetied with a cotter pin, that it is automatically safer".
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Last edited by rvbuilder2002 : 03-01-2014 at 11:44 AM.
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03-01-2014, 11:25 AM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Quote:
Originally Posted by rvbuilder2002
In the few instances where a bolt is used as a pivot point (fwd and aft ends of rudder cables is a good example), a castle nut and cotter pin is specified.
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Yep, far as I recall the flap hinge is the only surface using the castle nut and cotter pin on my 10. But then, the 10 flap is not like the rest of the line.
And, yes, the plans do call out for the correct hardware.
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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