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  #1  
Old 11-22-2011, 07:21 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,406
Default Come on Folks... Attaching the Elevator correctly is NOT that difficult!

Why is it that so many folks can't seem to get this right, it's so simple but I find it incorrect so often its amazing

Today during a condition inpection, on a nicely built 8, I find all the elevator attach bolts loose (rod end to hinge), as soon as I find this I know what's coming... no or incorrect spacing on the center support bearing. Sure enough when I tightened all the bolts down so the rod end bearings can actually act like bearings rather than bushings, the elevator is locked up tight. Loosen the center bearing and voila the elevator comes back to life (actually because the bearings had not been acting as bearings for so long it took lots of lube and working them back an forth to free them up).

Then I check to see what was used for spacers and guess what, none there, nata, zippo... no spacers at all, not even a single lowly washer!

So now I am tasked with making the correct size spacers for the center bearing, not an easy task at this point unless I also want to remove the rudder (which by the way all those bolts were loose too and same situation with frozen bearings).

The process is simple when installing the elevator:
1) Tighten up all the elevator attach points except the center bearing, Hinge bolts SHALL NOT be loose! Elevators should move freely.
2) Make the correct (exact) size spacers out of tubing or whatever you prefer for both sides of the center bearing (they will be different sizes).
3) Install spacers made in step 2 and tighten down center bolt, elevators should remain free just like they were in step 1.
If the elevator binds up return to step 2. Do not loosen hinge bolts in order to free up elevator!

I literally find this condtion on 75% or more of the aircraft I inspect.

It seems that when folks find things binding their answer is to just loosen up the bolts

Rod end bolt SHALL be tight (torqued) so that the bearing can actually work as a bearing.

Thanks for your cooperation
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 11-22-2011 at 08:23 PM.
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  #2  
Old 11-22-2011, 08:44 PM
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Geico266 Geico266 is offline
 
Join Date: Feb 2005
Location: Huskerland, USA
Posts: 5,864
Default

Pictures! We need pictures!

As usual Walt you have hit on something we must be neglecting if you are finding 75% wrong.


Pictures of "wrong" and "correct" would be helpful.
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  #3  
Old 11-22-2011, 09:24 PM
DaAV8R DaAV8R is offline
 
Join Date: Jul 2009
Location: Lee's Summit, MO
Posts: 749
Default Fiber lock nus?

As long as we're talking elevator bolts I have a question. Why are we using fiber lock nuts on bolts that participate in a hinge or any rotating assembly? Every certified plane that I've ever been around used a castle nut and cotter pin in these applications.

Just curious what your thoughts are. I have read reports where people have found the nuts off at the aileron bellcrank bolt.
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Lee's Summit, MO
RV-8 - Empennage & Wings Done
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1946 Cessna 120
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  #4  
Old 11-22-2011, 09:40 PM
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Phil Phil is offline
 
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Location: Waco, Texas
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Walt,

Posts like this one and your flaring one are just the type we need.

Keep'em coming.
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  #5  
Old 11-22-2011, 10:01 PM
aerhed aerhed is offline
 
Join Date: Dec 2008
Location: Big Sandy, WY
Posts: 2,567
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Quote:
As long as we're talking elevator bolts I have a question. Why are we using fiber lock nuts on bolts that participate in a hinge or any rotating assembly? Every certified plane that I've ever been around used a castle nut and cotter pin in these applications.
This kinda illustrates what Walt is talking about. Apparently there are a number of builders who don't understand the different methods of securing a hinge point (bearing vs bushing). I actually see this on lots of bottom-feeder certified planes, and thee are "supposed" to have been done by licensed individuals. Another one that fuses me is grease on Cessna fowler tracks instead of lube in the roller bearing. Double Duh.
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  #6  
Old 11-22-2011, 10:20 PM
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Rick_A Rick_A is offline
 
Join Date: Oct 2005
Location: Jacksonville, FL
Posts: 1,573
Default One other point .....

I too had this problem but since Walt's was keeping me on the straight and narrow during the build, I had to get my elevators rigged correctly before my first flight. BTW, I thought it was just fine until Walt checked it and told me it not even close to being "fine".

It took me a few days of work to get it right because I needed to tweak more than just the spacers. I found that I had the bearings slightly mis-aligned, so I had to remove and re-install both elevators many times to get ALL 5 BEARING (2 in each elevator + the center bearing) in alignment.

I went from having quite a bit of drag (when all the nuts & bolts were tight) to having an elevator that would move freely with just the slightest touch. It was well worth the effort.
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  #7  
Old 11-22-2011, 10:29 PM
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az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
Exclamation

Quote:
Originally Posted by aerhed View Post
This kinda illustrates what Walt is talking about. Apparently there are a number of builders who don't understand the different methods of securing a hinge point (bearing vs bushing). I actually see this on lots of bottom-feeder certified planes, and thee are "supposed" to have been done by licensed individuals. Another one that fuses me is grease on Cessna fowler tracks instead of lube in the roller bearing. Double Duh.
If it's a bearing, Clamp it! (lock nut OK)

If it's a bushing, Cotter Pin it! (use a castle nut)

Should work for all cases ...and is certainly true on my certified Grumman...
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Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
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Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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  #8  
Old 11-22-2011, 10:49 PM
Geeman Geeman is offline
 
Join Date: Apr 2010
Location: Houston TX KDWH
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Quote:
Originally Posted by Phil View Post
Walt,

Posts like this one and your flaring one are just the type we need.

Keep'em coming.
I was thinking the same thing. I am getting ready to continue a build I purchased and this is the type of information I am trying to absorb.

Thanks Walt.
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  #9  
Old 11-23-2011, 02:16 AM
Lars Lars is offline
 
Join Date: Nov 2005
Location: Davis, CA
Posts: 1,190
Default

Getting the elevator to float freely with all 4 rod end fasteners, the center bearing fastener and the elevator pushrod bolt properly torqued, took me the better part of a month to get right, what with bending flanges, shimming bearings, etc. In my case, I had to tweak every steel bearing support bracket on the back of the horizontal stabilizer. Since the holes in the bearing support brackets aren't slotted to allow for production tolerances, it was made even more difficult. I burned up at least 30 hours just getting those parts right.

Hopefully that is not representative of a typical aircraft production environment. Because if it is, that would go a long way towards explaining why it's so expensive to build airplanes.
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  #10  
Old 11-23-2011, 02:23 AM
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islandmonkey islandmonkey is offline
 
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Location: Zurich, Switzerland
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Why oh why would anyone put forward an aircraft for condition inspection in the state that Walt describes??

I would be mortified if I presented work like that for inspection.
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