MKIV Bent elevator control

25 posts in this topic

Posted

Hello All,

I noticed today that the thread on my elevator control rod on the Avid is bent.  I know there is an AD to ensure that an elevator stop is installed.....and it is.  Never the less it is bent and thus buggered.

I also notice that it would appear the control rod has been repaired in the past as there is a weld in it.  I have a few questions.

1) It does not appear that you can remove the control rod out of the fuselage without cutting it as it will not fit through the bushes.  Is this correct or further signs of a completely buggered control rod.

2) Is there a standard/recommended/mandatory method to repair the bent thread?  I know straightening is not an option.....

3) If the control rod has already been repaired/welded in the past, should it be repaired/welded again?

 

 

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Posted

you could just cut it off further back or in front of the current welds.  Mine has been bent for 700+ hours and I still fly it that way.  One day I might get energetic and replace the end.  A good Tig welder can fit it right up for you.  Another "fix" would be to cut the tube off and weld a new threaded end onto the next size up tubing then slip it over your tube and use SS rivet to put it back on.  If the rivets will hold the sing struts etc. they will work just fine on the elevator rod. 4-6 rivets and I would not think twice about flying it.  In fact, you just talked me into fixing mine that way, it would be a 20 minute fix on the plane once you have the new end welded up on another tube.

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Posted

Where is the stop for the elevator?  I use a piece of aluminum angel screwed to the floorboards to stop the forward motion of the joy stick.  Simple, and it works.  JImChuk

PS  pay no attention to the dirty carpet.............

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Posted

Mine is bent also. It has to be to get full down elevator as that provides the clearance around the tube running side to side. Yes I use full down to pick up the tail on take off and also performing outside loops and snap rolls (just kidding on the last 2)!

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Posted

I am in the UK so life is so much more difficult.  With it bent I cannot renew the annual permit to fly as there has been a few accidents where it has sheared due to fatigue from the bent thread. Also any welding has to be done by a CAA approved welder and not just by anyone that can weld.

 

As for the stop in the UK it has to be done like this:

 

http://www.lightaircraftassociation.co.uk/engineering/TADs/189/PFA MOD 189 006 Elevator Stop 030807.pdf

 

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Posted

Personally  I would not trust a bent primary flight control rod....could be fine.....or could crack and break!!!!!! You're probably 3 feet under when it does breaks. I had the same thing happen on my catalina. On the catalina Avid recognized this and introduced a safety strap for redundancy (besides the stop), below the picture for you.

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Posted

Flywise, I like that safety strap.  Would really be useful in trailering situations where controls can get bounced pretty good even with surface locks at times.  Good thread to bring this info out!

:BC:

 

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Posted (edited)

Leni,  I think you hit it with the aircraft spruce threaded rod end.  And it would eliminate any welding for our English friend.  Could maybe even drill one 3/16" hole through the tube with the rod end in place, and put a AN 3 bolt through there to hold it all together.  That would then be the same size as the bolt going through the heim joint end.  No way it would let go...... Just another thought.  JImChuk

PS  this thread also shows the importance of gust locks when trailering

Edited by 1avidflyer
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Posted

Excellent thanks guys.  I think the AN430 idea might be a brilliant option, but I am fairly sure that UK regs will require it to be welded.  Either way I think it is the best option.

 

FLywise, have you got any more pics of that safety strap mod?  that's another great idea.

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Posted

Leni,  I think you hit it with the aircraft spruce threaded rod end.  And it would eliminate any welding for our English friend.  Could maybe even drill one 3/16" hole through the tube with the rod end in place, and put a AN 3 bolt through there to hold it all together.  That would then be the same size as the bolt going through the heim joint end.  No way it would let go...... Just another thought.  JImChuk

PS  this thread also shows the importance of gust locks when trailering

That is my plan.  Turn it into a 30 minute fix if you stop and drink a beer and play with the ole lady for a few minutes.  Lil epoxy, drill and bolt and your done.  If for some reason you happen to do it again you can do a quick swap down the road.  I am with you, no way it will let go and I would actually have better peace of mind bolted versus welded as it will be a pain in the ass to weld in place going around the bottom side.  I guess a few rosette welds would be easy to do too but why do that when bolted would still be "overkill".

Like dear ole daddy always said before he departed this shitty world.. "If you wanna know the easiest way to get something done ask the laziest man on the crew.. that would be me".  :lmao:

:BC:

 

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Posted

Here the Avid paper for the safety strap install...

P1110002.JPG

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Posted (edited)

https://www.aircraftspruce.com/catalog/appages/an490.php?clickkey=107752

 

This is what I ordered to fix my bent threaded end.  cut the old one off, insert and weld.  Or glue and rivet/bolt.

:BC:

 

Was this for an Avid or Kitfox?  I ordered one, but the thread is way to big.  So I need to figure out what thread I need.  As usual my manual doesn't list the item other than calling it and elevator push rod.  So I though I know I will look up the heim in the manual....naturally the manual simply calls it a rod end with no other information :) ....well it labels it as F-40.

Edited by Gfry

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Posted

So further research.  The rod end that is on the aircraft is an Aurora MW-3M-1 Which turns out to be a special part from Aurora which is no longer available.  it was a 10-32 thread.  So now I need to find a threaded rod end that fits 1/2 inch tube and has a 10-32 thread.  not an easy task int he UK :)

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Posted (edited)

So further research.  The rod end that is on the aircraft is an Aurora MW-3M-1 Which turns out to be a special part from Aurora which is no longer available.  it was a 10-32 thread.  So now I need to find a threaded rod end that fits 1/2 inch tube and has a 10-32 thread.  not an easy task int he UK :)

No wonder that these are bending & breaking, with tiny 10-32 threads!  Kitfox uses 1/4-28 threads which are much stronger.  You can buy those too.  EDMO

Edited by EDMO

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Posted

I would have bet the tube end had 1/4 -28 threads.  See if you can get a 1/4" threaded heim joint.   JImChuk

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Posted

I would have bet the tube end had 1/4 -28 threads.  See if you can get a 1/4" threaded heim joint.   JImChuk

Or check on equivalent Aurora part - They are usually cheaper and have same specs.  EDMO

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Posted

Maybe get a new rod end bearing that has 1/4" hole in the bearing and 1/4" threads and that way it will work with your new 1/4" threaded rod end.  You would have it fixed and its stronger!!!

Like this one but obviously you can find them other places too.

https://www.ebay.com/itm/AHFT4-NMB-Stainless-New-Rod-End-Bearing-1-4-28-Thread-1-4-Hole-Aircraft-Grade/291857085541?epid=705030831&hash=item43f409b465:g:YFwAAOSw6n5XwLJ2

Cheers Randy

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Posted (edited)

Thanks....although the part that someone else bought for their repair (which I have now  bought) is 3/8"-24 thread and I cant seem to find a heim rod end with that thread that has the right size bearing:)  Also the rod end bearing hole is only 3/16 as is the bolt hole on the bracket.

 

I either have a wierd MkIV or most of you are refering to a KitFox:huh:

Edited by Gfry

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Posted

I went and pulled my F40 and it is a 3/16" hole in the rod end bearing with 1/4" threads which is what the manual/drawings show.  (Sorry for the reference of the 1/4" hole above as I must have misread one of the original posts as I thought you mentioned you had a 1/4" hole).  Just as Leni mentioned I bet it was a 1/4" originally and whoever fixed it last time put some odd fitting on there and made it work.

I think your best bet would be to get the correct threaded rod end 1/4" as Leni provided earlier and get yourself a new rod end bearing with 3/16" hole and 1/4" threads.  This would be rather inexpensive and less headache then trying to match the other threads you have now.

Funny thing is after looking at the drawings and manual some more it shows on my drawing that it is an AN4 bolt through the end of this bearing but that is not correct as it is an AN3 size hole in the control column and the rod end bearing.  I was planning on working on some of this later today on my kit.  Looks like I'm going to have some fun figuring out the mix up!  Cheers Randy

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Posted

Yes weird it shows an AN4 bolt.....  Mine is a 1 1/32 AN3.  At least I have the correct bolt :wacko:

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Posted (edited)

Guess that I too, should have been more specific - Kitfox uses 1/4-28 threads with 3/16 crossbolt.  I may have the numbers for it, or even a spare, but you should be able to find them in Spruce catalog.  I really like the extra strap that was shown on the Catalina.  Good Show!  EDMO

Edited by EDMO
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Posted

I would say that strap was a Great addition but it's a shame it never made it to the other manuals!  Thanks to flywise....I bet there will be many of those made/added.

Ed, glad to see your still keeping at!  Hope all is going well for you!  Cheers Randy 

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Posted

I have emailed Mark twice about the check strap now...the first time being 9th April........No response.

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Posted

Yay, 1/4-28 threaded rod end arrived,  1/4-28 with 3/16 bearing hole rod end arrived.  Now I need to submit a mod to install them and pray to god I am allowed to secure with 2x 1/8 rivets slightly staggered at right angles.  Else it would have to be welded and for that the CAA have to send a coded welder to do it.....at great expense.

You guys in the US have it easy with your experimental system.  Saying that our "Experimental" system in the UK is still way easier than the normal C of A regime.

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