Covers for Flap and Aileron Hinges.

Bcone1381

Bcone1381

Finished Patrol
I have a question or two on the Hinge Covers for the Flap and Aileron.

Background.....In Beartracks Q1 of 2006 the covers are documented and instructions are to secure them with 3/32" AL pull rivets. (In 2015 one of the covers dimensions changed. https://bearhawkforums.com/forum/saf...cket-cover-jam )

My question is this. Do these covers typically get removed after they are installed? Thats my impression, but I am re-evaluating it. I'm envisioning the kernels of a drilled out pull rivet floating around inside the flight controls every time they were removed. That cant be, but maybe there is a way to remove the kernels after they get drilled out. I want to stay away from riv-nuts.
 
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Those covers are rarely removed. You can always use pops on one side (like the tops) and little sheet metal screws on the other. That would allow you access when/if needed. Mark
 
Refer to the latest guidance about the size of these covers, if they are made incorrectly and they come loose then they can jam control surfaces.
I used screws, the only time I have ever removed them was when I needed to disassemble the wing after things got bent.
While removing them is rare, I was pleased not to have to drill out pop rivets. The drilled off rivet heads would probably get stuck somewhere inside the aileron and drum a hole in the fabric.
 
We flew for 55hrs without these covers. We took the flaps and ailerons off several times during that time. Now that things are properly rigged I don't see a reason we'd ever remove them again, except as noted below. We still chose to use screws to install the covers.

Note: Due to it being harder to see/touch the bolts that attach the flaps/ailerons I wish we had used drilled bolts and cotter pins. This is a change we will make at the next annual.
 
whee said:
We flew for 55hrs without these covers. We took the flaps and ailerons off several times during that time. Now that things are properly rigged I don't see a reason we'd ever remove them again, except as noted below. We still chose to use screws to install the covers.

Note: Due to it being harder to see/touch the bolts that attach the flaps/ailerons I wish we had used drilled bolts and cotter pins. This is a change we will make at the next annual.
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Ahhh! I had not thought of that. I'll do the same.
 
whee said:
Note: Due to it being harder to see/touch the bolts that attach the flaps/ailerons I wish we had used drilled bolts and cotter pins. This is a change we will make at the next annual.
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I believe this should have been picked up by the DAR (?) as it doesn't strictly comply with AC43.13B?
 
Battson said:
I believe this should have been picked up by the DAR (?) as it doesn't strictly comply with AC43.13B?
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The heim joint has a bearing so technicaly nothing is turning on the bolt so it doesn’t need a cotter pin. Still, I will be changing to cotter pins and drilled bolts. A strict reading of 43.13 would require drilled bolts and pins on the landing gear....

Pretty sure I used the hardware designated...somewhere, one of the manuals.
 
whee said:
The heim joint has a bearing so technicaly nothing is turning on the bolt so it doesn’t need a cotter pin. Still, I will be changing to cotter pins and drilled bolts. A strict reading of 43.13 would require drilled bolts and pins on the landing gear....

Pretty sure I used the hardware designated...somewhere, one of the manuals.
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Yes, I did use cotter pins on all those landing gear bolts. Same with all flaps and aileron surfaces, plus trim surfaces.
Can't be too careful.

I agree that the manuals call out the wrong bolts in this case.
 
I think the manual is in accordance with what Tony Bengelis wrote on this topic.....

"you can use self-locking nuts in a pulley installation, in a rod end bearing installation or against an anti-friction bearing where the nut tightly binds against the inner race of the bearing or against a part of the fitting that tightly binds the inner race of the bearing. Figure 4 has an example shown."
Screen Shot 2019-11-11 at 8.16.40 AM.png
 
As you show here Brooks, the BH manual is accurate in specing self locking nuts. I thought they were fine until we put the pocket covers on. Now I have a hard time seeing the bolt/nuts and can not touch them...I don’t like that thus I’m going to change them.
 
whee said:
The heim joint has a bearing so technicaly nothing is turning on the bolt so it doesn’t need a cotter pin. Still, I will be changing to cotter pins and drilled bolts. A strict reading of 43.13 would require drilled bolts and pins on the landing gear....

Pretty sure I used the hardware designated...somewhere, one of the manuals.
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Nylocks on gear bolts has always confused me. Not sure why so many people do that and it's become standard practice when it's not correct.
 
zkelley2 said:
Nylocks on gear bolts has always confused me. Not sure why so many people do that and it's become standard practice when it's not correct.
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Agreed, the gear bolts should be drilled and secured with cotter pins. If the manual says otherwise, it is an error that we can fix, if someone knows where it says that.
 
I'm not sure off the top of my head what it says. I'm just saying in general. If I take a walk through the ramp at hood, probably half the aircraft with gear leg attachment like ours have locking nuts. Certified or experimental.
 
Click image for larger version Name: 69541236_10111598700552930_7319955596281643008_o.jpg Views: 0 Size: 318.5 KB ID: 50470
Here's a really good example of how not to do it.
All you can do is laugh.

I've also seen that pictured, but with a cotter pin after the locking nut. It's like um.... I guess that won't fail, but how about no.
 
I’ve only seen a few BHs in person and they all had self locking nuts on the gear. I didn’t like it but that is what the Avipro manual called out. When I asked Bob about it he said it is not and issue so I went it with. My DAR didn’t question it but I had a friend who’s plane failed inspecion and the self locking nuts on the gear was on the punch list.
 
Bcone1381 said:
I think the manual is in accordance with what Tony Bengelis wrote on this topic.....

"you can use self-locking nuts in a pulley installation, in a rod end bearing installation or against an anti-friction bearing where the nut tightly binds against the inner race of the bearing or against a part of the fitting that tightly binds the inner race of the bearing. Figure 4 has an example shown."
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To be fair, we need to refer to AC43.13B

If the aurora bearing seizes - this is not unheard of - then the nut is subject to rotation. Hence AC43.13B Part 7 Section 4 expressly prohibits the use of self-locking nuts.

That section is pretty much dedicated to when you mustn't use self locking nuts. That is an implicit message, if you read between the lines...

The nut can work it's way free if the bearing seizes, and you may never notice until the nut works it's way off. Aurora bearings can definitely corrode and lock up, especially in a coastal environment.

Ultimately it's up for interpretation, because the AC is not exhaustive. The safest approach is using a castle nut.
 
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Battson said:
To be fair, we need to refer to AC43.13B

If the aurora bearing seizes - this is not unheard of - then the nut is subject to rotation. Hence AC43.13B Part 7 Section 4 expressly prohibits the use of self-locking nuts.

That section is pretty much dedicated to when you mustn't use self locking nuts. That is an implicit message, if you read between the lines...

The nut can work it's way free if the bearing seizes, and you may never notice until the nut works it's way off. Aurora bearings can definitely corrode and lock up, especially in a coastal environment.

Ultimately it's up for interpretation, because the AC is not exhaustive. The safest approach is using a castle nut.
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I totally agree with you Battson, the safest approach is a castle nut and I wish I had used them. Would save me from having to redo work...again.

However...

AC43-13-1B Par 7-64-d

d. Self-locking nuts should not be used with bolts, screws, or studs to attach access panels or doors, or to assemble any parts that are routinely disassembled before, or after each flight. They may be used with anti-friction bearings and control pulleys, provided the inner race of the bearing is secured to the supporting structure by the nut and bolt.
 
It’s worth noting that AC 43.13-1B is advisory in nature, as the name implies, so strict compliance isn’t a regulatory requirement here in the US. It’s also kind of out of date, last released 9/8/98. Section 7-64(a) states “DO NOT use self–locking nuts on parts subject to rotation”… seems pretty unambiguous, and one can see how this might mean pulleys and bearings as well.

The “Aviation Maintenance Technician Handbook- General” (FAA-H-8083-30A) provides for pulleys and bearings. From Page 7-44: “Do not use self-locking nuts at joints, which subject either the nut or bolt to rotation. They may be used with antifriction bearings and control pulleys, provided the inner race of the bearing is clamped to the supporting structure by the nut and bolt.”

To me this explains the reasoning behind why it’s ok to use self-locking nuts on pulleys and bearings (when captured as described), but not on the landing gear hinge. The former are specifically designed to be anti-friction and only if they fail will they then be functionally equivalent to the latter, so you have some redundancy in those joints. The figure Bcone attached complies with the AMT handbook, if the bearing seized it would then just be rotating around the bolt and (hopefully) not be imparting enough force to rotate it. Not ideal but probably plenty safe to keep flying until you discover the seized bearing at the next annual.

I have castle nuts for my gear bolts and will be using them for any rotating assembly, for good measure.
 
whee said:
I totally agree with you Battson, the safest approach is a castle nut and I wish I had used them. Would save me from having to redo work...again.

However...

AC43-13-1B Par 7-64-d

d. Self-locking nuts should not be used with bolts, screws, or studs to attach access panels or doors, or to assemble any parts that are routinely disassembled before, or after each flight. They may be used with anti-friction bearings and control pulleys, provided the inner race of the bearing is secured to the supporting structure by the nut and bolt.
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Sorry Jon - but...

I am a stickler for Engineering detail and I know you are too... so here goes.

Engineering.com said:
Sliding contact bearings are referred to as plain bearings and rolling contact bearings are often called antifriction bearings.
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Anti-friction bearings as found in the typical pulley or other device are not the same an aurora bearing on the rod ends for flaps and ailerons.

Therefore AC43-13-1B Par 7-64-d does not apply for flaps and ailerons. We need to use castle nuts and the DAR should have picked this up if they know their trade well.
 
Battson, I appreciate the correction. You are certainly right. I obviously didn't know what defines a anti-friction bearing and never thought to look it up. The IA that that help us restore a Luscombe had us to use nylock nuts on the rod-ends and the following IA that did annuals never asked for them to be replaced. Looks like some A&P schools need a bit of education on bearings. Maybe a good topic for IA refresher training.
 
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