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Flap linkage bolt

dromuald

Active Member
I thought I would share this discovery since I appreciate other posts when members share important issues. I was performing my annual condition inspection with my local A&P. I decided to pull the interior side panels of my RV-8 to inspect the flap linkage. I had recently made the mistake of taking off with full flaps and although I was confident I didn't overspeed the flaps I thought it would be worth a look. To my surprise I found that the nut on the bolt which connects the flap motor to the linkage almost completely backed off. Although it has a nylon insert this nut could be turned with my fingers.

I have owned the a/c for five years (not the builder) and regret that this was never checked on my previous condition inspections. I can't vouch for whether or not the nut was installed properly but I do see some evidence that a wrench was used on the nut prior to this photo.

Although I have no idea as to why this nut came loose I thought it would be something of interest to this forum.
01a9e97fd44ebacfc8c41519862151b58de02ff535_1.jpg.html
 
Good catch. I doubt it came loose. I have seen more than one nut on an airplane that was never tightened. :)

Vic
 
Probably missed torquing in construction.

I agree with Vic on this one since I just completed my own flap installation. If the bearing is properly installed, the bolt should never have the opportunity to turn at all if torqued to specs.
 
Good catch. I doubt it came loose. I have seen more than one nut on an airplane that was never tightened. :)
Vic

My self! What bothers me is that lately I've been finding loose nuts with torque seal on NEW aircraft.
 
My self! What bothers me is that lately I've been finding loose nuts with torque seal on NEW aircraft.

That's mind-boggling. I don't think someone understands the objective of using torque seal!

Vic
 
I thought I would share this discovery since I appreciate other posts when members share important issues. I was performing my annual condition inspection with my local A&P. I decided to pull the interior side panels of my RV-8 to inspect the flap linkage. I had recently made the mistake of taking off with full flaps and although I was confident I didn't overspeed the flaps I thought it would be worth a look. To my surprise I found that the nut on the bolt which connects the flap motor to the linkage almost completely backed off. Although it has a nylon insert this nut could be turned with my fingers.

I have owned the a/c for five years (not the builder) and regret that this was never checked on my previous condition inspections. I can't vouch for whether or not the nut was installed properly but I do see some evidence that a wrench was used on the nut prior to this photo.

Although I have no idea as to why this nut came loose I thought it would be something of interest to this forum.
01a9e97fd44ebacfc8c41519862151b58de02ff535_1.jpg.html

Hi Dave,

Glad this didn't end up causing trouble. I need to check my plans but I'm pretty sure this bolt should have a castle nut and cotter pin rather than a nylock.
 
Originally Posted by vic syracuse View Post
Good catch. I doubt it came loose. I have seen more than one nut on an airplane that was never tightened.
Vic

Vic, we talking about nuts and bolts or the pilot/mechanic never tightened up properly.:D
 
Hi Dave,

Glad this didn't end up causing trouble. I need to check my plans but I'm pretty sure this bolt should have a castle nut and cotter pin rather than a nylock.

Castle nuts and cotter pins I believe are only used on bolts that will normally rotate. The rotation on the flap bearing should only be in the bearing.
Mel?
 
It should have a cotter pin.



The plans specifically call out:

AN4-11 Bolt
AN960-416 Washer
AN310-4 Nut
MS24665-208 Cotter Pin

I just replaced these the other week.
 
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The plans specifically call out:

AN4-11 Bolt
AN960-416 Washer
AN310-4 Nut
MS24665-208 Cotter Pin

I just replaced these the other week.
That's absolutely true Jeff but I believe he's referring to the linkage that connects to the flap, not the flap motor.
 
Castle nuts and cotter pins I believe are only used on bolts that will normally rotate. The rotation on the flap bearing should only be in the bearing.
Mel?

My understanding is that the bolt in question is the one that captures the end of the flap motor. There's no bearing there, just a hole in the motor casing that will tend to rotate the bolt. Hence the need for a cotter pin.

If its the bolt holding the flap control rod then yes, it has a rod-end bearing.
 
My understanding is that the bolt in question is the one that captures the end of the flap motor. There's no bearing there, just a hole in the motor casing that will tend to rotate the bolt. Hence the need for a cotter pin.

If its the bolt holding the flap control rod then yes, it has a rod-end bearing.

I got it now. That photo shows a motor right over the flap linkage. Mine is centered. I never considered the motor being mounted on the side.
 
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As its shown unless otherwise specified as my grey matter says if the object the nut and head of bolt does not rotate you don't have to put a castle nut with cotter key on. If the item that is secured by the nut and bolt rests against the bolt or nut if I can explain it right, such as if it only had one tab instead of two then the castle nut assembly would be the proper way. I don't have the FAR to refer to.............anyone? But if the manufacture says to do something in there instructions you follow that.
Again anyone? Boyd
 
I see evidence of both tightening and loosening on that nut. Nylocks are not to be reused. They are not effective on second use since the nylon will be deformed by the previous use.
 
Not quite true......

I see evidence of both tightening and loosening on that nut. Nylocks are not to be reused. They are not effective on second use since the nylon will be deformed by the previous use.

Nylock nuts may be reused as long as the nut cannot be "turned by hand". ref. AC 43-13. Many people have their own rule of thumb. Some use them only once. Some use them only 3 times. etc.
 
There should be at least one thread showing beyond the nut when properly torqued. The photo show some gap. Verify that the proper bolt is being used per the plans.
 
There should be at least one thread showing beyond the nut when properly torqued. The photo show some gap. Verify that the proper bolt is being used per the plans.

Looks more like it was never tightened or had been and did not lock due to too much use as per regs on nylon lock nuts. The gap is wrong due to one or those two items.
Also due to the way its used don't think one would torque it, should be just snug as they need the actuator to be able to move so it can stay aligned.
 
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Looks more like it was never tightened or had been and did not lock due to too much use as per regs on nylon lock nuts. The gap is wrong due to one or those two items.
Also due to the way its used don't think one would torque it, should be just snug as they need the actuator to be able to move so it can stay aligned.

And it needs to have a cotter pin! As has been stated earlier in the thread. Seems to me that should be the end of the conversation.......... :rolleyes:
 
And it needs to have a cotter pin! As has been stated earlier in the thread. Seems to me that should be the end of the conversation.......... :rolleyes:

Should be the cotter pin is called for along with the proper nut. The comment was about the existing nut by the way. Didn't mean to get anyones dander up. Boyd ps roll my eyes ho hum
 
To answer the question, I don't think it was ever tightened. That being said, I went to look at the plans as I thought it needed a drilled bolt, but I see it's already been posted.

That's what I get for being busy out doing demos. :)

Vic
 
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