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  #1  
Old 11-20-2019, 09:14 PM
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Pilot135pd Pilot135pd is offline
 
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Location: Vaca Moo Airport - TA37 in East TEXAS
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Default Wrong Rudder Cable Nut and Missing Cotter Key

I just read an article in a magazine that left me very confused regarding my RV-8. I?m not a mechanic or a builder so it might have a simple explanation but if not I found it to be a major safety issue.

This is what the author said:

?Wherever a bolt is subject to rotation, it is required to have a castellated nut and cotter key. A typical mistake I see on amateur-built aircraft is the use of a heat nut or fiber nut on the rudder control horn. The second picture shows the proper bolt/nut combination; however, the cotter key is missing.?

So I went and looked at every one of the nuts on my ailerons, rudder, and elevator and they don?t have cotter pins. Aren?t those bolts subject to rotation?
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  #2  
Old 11-20-2019, 09:23 PM
eddieseve eddieseve is offline
 
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Those nuts and bolts lock down onto a bush and only the bearing is meant to move.

Cheers
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Last edited by eddieseve : 11-20-2019 at 09:25 PM. Reason: Possible mistake
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  #3  
Old 11-20-2019, 09:24 PM
PCHunt PCHunt is offline
 
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Quote:
Originally Posted by Pilot135pd View Post
............. So I went and looked at every one of the nuts on my ailerons, rudder, and elevator and they don’t have cotter pins. Aren’t those bolts subject to rotation?
Do a search on VAF, this issue has been discussed many times. Short answer: The hinge bolts on the flight controls are NOT subject to rotation, and MUST be torqued to proper spec. Nyloc nuts are OK. It's NOT OK to leave these nuts untorqued. That's because there is a bushing inside the hinge that is slightly longer than the gap, and the bushing does not rotate. The hinge rotates on the fixed bushing.

The rudder cable attach bolts are a different story, they DO rotate, hence the need for castellated nuts with cotter pins.

Hope this helps, but a search will turn up much more........
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Last edited by PCHunt : 11-20-2019 at 09:26 PM. Reason: Add clarifying info
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Old 11-20-2019, 09:50 PM
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Pilot135pd Pilot135pd is offline
 
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Thanks to both answers. I always do searches on this forum and have learned a lot but this caught me by surprise and I kind of freaked out that I’ve been flying it like that.

In hindsight it was built by an A&P who has built another RV plus it did pass a Condition Inspection by a A&P IA who is also an RV builder and I guess he would have caught that.

Also part of my preflight is to make sure there’s thread sticking out of those nuts anyway but it worried me when I read that article.
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Old 11-21-2019, 05:49 AM
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Walt Walt is offline
 
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I saw that picture as well and would debate it being called "unairworthy".
Relative motion (minimal in this case), is somewhat debatable and according to the AC:

"Self-locking nuts alone should not be used in any system when movement of the joint may result in motion of the nut or bolt head relative to the surface against which it is hearing."

So in the noted rudder fork the bolt would have to seize in the rudder horn for any relative motion to be exerted. The AC goes on to say:

"Joint seizure (bearing, unibal, or bushing seizure) does not have to be considered by this regulation when determining the relative motion of the parts in question, although it is advisable to do so.

So assuming this joint is checked and lubricated regularly (condition insp or pre-flight) it should be fine... is a cotter keyed bolt good, sure, is the aircraft unairworthy because of this installation, not in my opinion.

Flame suit on...

https://www.faa.gov/documentLibrary/...C_23_607-1.pdf

https://www.boltscience.com/pages/se...-fasteners.pdf
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Last edited by Walt : 11-21-2019 at 06:03 AM.
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Old 11-21-2019, 06:00 AM
Jpm757 Jpm757 is offline
 
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On those locations where Van calls for lock nuts, I choose to use a stronger metal lock nut, and apply a dap of torque seal to detect any rotation on preflight. Keeping these bearings adequately lubricated is essential, especially for aircraft stored outdoors.
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Last edited by Jpm757 : 11-21-2019 at 06:02 AM. Reason: Ad
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Old 11-21-2019, 07:18 AM
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Pilot135pd Pilot135pd is offline
 
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Quote:
Originally Posted by Jpm757 View Post
On those locations where Van calls for lock nuts, I choose to use a stronger metal lock nut, and apply a dap of torque seal to detect any rotation on preflight. Keeping these bearings adequately lubricated is essential, especially for aircraft stored outdoors.
I keep mine in a hangar and check those religiously on preflight, should I spray a little WD40 on them to keep them lubricated or are they lubricated enough at anual ? I think it might be worse if I spray it since I fly out of a sometimes dusty grass runway.
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Exempt by 3 out of the 10 ways but I still donated.
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  #8  
Old 11-21-2019, 07:24 AM
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Quote:
Originally Posted by Pilot135pd View Post
I keep mine in a hangar and check those religiously on preflight, should I spray a little WD40 on them to keep them lubricated or are they lubricated enough at anual ? I think it might be worse if I spray it since I fly out of a sometimes dusty grass runway.
Use LPS1 instead of WD 40. LPS1 is greaseless and will not attract dirt, penetrates and provides lubrication when dry.

Here is a link to more info about LPS1

https://www.lpslabs.com/product-details/560

Personally I would not use WD40 on anythng on my plane. Just my opinion.
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  #9  
Old 11-21-2019, 07:46 AM
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Pilot135pd Pilot135pd is offline
 
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Yes I have LPS products, WD40 was a bad example. My main question is are they lubricated enough at anual ? I think it might be worse if I spray it since I fly out of a sometimes dusty grass runway.
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RV-8 N52VM: OnSpeed Gen2 AOA-3D, Dynon D-180, Autopilot, Titan 0-360A1A, Hartzell C/S, INS-429 IFR & GPS496, WingX & Stratux for backup & ADS-B IN. Enjoying life while building an airpark with FREE campsite for pilots www.facebook.com/VacaMooAirport/

Exempt by 3 out of the 10 ways but I still donated.
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  #10  
Old 11-21-2019, 07:56 AM
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Quote:
Originally Posted by Pilot135pd View Post
Yes I have LPS products, WD40 was a bad example. My main question is are they lubricated enough at anual ? I think it might be worse if I spray it since I fly out of a sometimes dusty grass runway.
I also keep mine in a hanger and about every couple of months during a preflight will hit all the flap and control surface hinges with a shot of LPS1 just as a precaution. I would not leave it for once a year. Also if I have flown through rain or had the plane on a ramp in rain I will hit all the hinges with LPS1 once I get back to the hanger.
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