Citabria Wing strut attach fitting 1000 hour inspection

Joesf

Well-known member
Joined
Nov 12, 2018
Messages
47
Does anyone know where to find these service letters? They are omitted from American Champion site. I am interested in SL 415. I am close to having to do this.

Thank you
Joe


American Champion has designed improved wing front strut attach fittings, part number (P/N) 3-1691 and P/N 3-1692, which, when manufactured according to design specifications, will not contain the surface deformities and scratches found on the existing design fittings. After extensive analysis, these fittings have proven to not have the cracking susceptibility of those currently in service. The following presents service information that American Champion has issued that relates to this issue:
* American Champion Service Letter (SL) 408, dated January 24, 1996, and American Champion SL 409, Revision A, dated April 22, 1996, which specify procedures for accessing and inspecting wing front strut attach fittings, part number (P/N) 3-1632-1 and P/N 3-1632-2; and P/N 3-1646L and 3-1646R, respectively.
* American Champion SL 410, dated May 6, 1996, which includes procedures for installing removable inspection hole covers for the wing front strut attach fittings on Model 8KCAB airplanes that have complied with American Champion SL 408;
* American Champion SL 411, dated May 6, 1996, which includes procedures for installing removable inspection hole covers for the wing front strut attach fittings on Model 8KCAB airplanes that have not complied with American Champion SL 408;
* American Champion SL 412, dated May 6, 1996, which specifies procedures for installing removable inspection hole covers for the wing front strut attach fittings on Models 7ECA, 7GCAA, 7GCBC, and 8GCBC airplanes that have complied with American Champion SL 409;
* American Champion SL 413, dated May 6, 1996, which specifies procedures for installing removable inspection hole covers for wing front strut attach fittings on Models 7ECA, 7GCAA, 7GCBC, and 8GCBC airplanes that have not complied with American Champion SL 409.
* American Champion SL 414, Revision A, dated June 25, 1996, which specifies procedures for replacing the wing front strut attach fittings on Model 8KCAB airplanes with improved wing front strut attach fittings, P/N 3-1691, and also includes procedures for inspecting the wing front strut attach fittings on these airplanes; and
* American Champion SL 415, Revision A, dated June 25, 1996, which specifies procedures for replacing the wing front strut attach fittings on Models 8GCBC, 7ECA, 7GCAA, 7GCBC, and 7KCAB airplanes with improved wing front strut attach fittings, P/N 3-1692, and also includes procedures for inspecting the wing front strut attach fittings on these airplanes.
 

Joesf

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Joined
Nov 12, 2018
Messages
47
Sully ,
Thanks a bunch. I didn’t have any success finding them anywhere else. I don’t know how you did it. Another angel gets his wings.!
Joe
 

cman

New member
Joined
May 10, 2019
Messages
2
I see that the inspection is required, but where is it specified this inspection is due at 1,000 hrs. I must have missed that somewhere.
 

Handysmurf

New member
Joined
Jan 11, 2020
Messages
4
AD 96-18-02 Mandatory 1000 flight Hour interval of Wing Strut Attachment
fittings P/N 3-1692.
DISSASSEMBLEY IS NOT THE PROBLEM – HOWEVER RE-ASSEMBLY RESEMBLES SOMETHING LIKE PUTTING the GENIE BACK IN THE BOTTLE!

These instructions are dedicated to next poor bastard mechanic who finds themselves forced to carry out an inspection with in-adequate technical information.

Before you even start – this inspection is not for the faint hearted. It requires a least one other person on occasions. A wing trestle is required, as is a study trestle to support the tail. If you happen to be working on a Scout 8GCBC unless you are a heavy lifter, you’ll need someone to help lift the tail onto the trestle. Of course there are always ways around – you may find you can incrementally lift the tail by means of a floor jack placed under the tailwheel, where you can get enough height to squeeze regular wing jack under the tail-spring through bolt. I still recommend having a trestle under the tail – you can’t be too cautious and the consequences of an aircraft either falling off a jack or the jack failing can be ugly.

If you have any doubts in your ability – you may simply wish to advise the owner to have this inspection carried out at the American Champion Aircraft Factory. Judging by the scant technical info available on this subject, I would hazard a guess this may happen more often than one would think.

For this particular inspection, the aircraft in subject was a 2012 8GCBC Denali Scout with the IO-390-A1B6 engine and thus all findings pertain to this aircraft – however since this is the heaviest variant American Champion makes, I can only conclude that all other models would be easier.

In my particular case I was lucky in so far as I have an adjustable wing truss/support stand and given the weight and height of the 8GCBC I believe it would have been extremely difficult to carry out the inspection without this tool.

The adjustable nature of the wing truss/support stand, meant there was no need to adjust the aft support strut.

In my particular case – Service Letter 415 was applicable – but this yields scant information as to how to actually carry out the inspection or more importantly get the parts back together.

Special Tools and equipment required:
Torque Seal or witness paint
.041 Annealed Brass Safety Wire
5/32” open ended wrench
Bicycle spoke tool
4’ of ½” EMT
1.5 – 2’ of ½” threaded rod and 1 nut
Torque Wrenches with a range down to 50 inch lbs and up to 400 inch lbs







Steps:

  • Chock Main Wheels
  • Place tail/tailwheel on tail-stand, such that the fuselage is as horizontal as possible.
  • Place support stand outboard of wing strut such as to support the weight of the wing.
  • Remove Jury Struts
  • Remove the rear strut entirely
  • If the main strut has speed fairings – these must be undone and slid down the strut out of the way.
  • Remove at least the outboard attach bolt for the main strut. If not removing the strut altogether, then after removing the AN6 wing Mounting bolt, rest strut on suitable trestle or support stand.
  • Next open up the inspection hole directly behind the main strut attach point (behind the main spar) if not already open.
  • You will see two drag wires and a spreader bar, follow the angle of those drag wires to the relevant inspection holes. If this is a newer aircraft and the inspection has never been completed, you will need to open up those holes.
  • New attach hardware is strongly suggested or at the very least new nuts.
  • Once the plates are roughly back in place and the tie-down bolt is back in you are faced with getting the Genie back in the bottle, namely the working out how to get the spreader bar back in place with the drag-wire plate such that you can re-insert the retaining bolt back through the main spar. Only one person at the factory shed some light on the matter – only to say that this was the first task they carried out before attempting to install the other bolts, by trying to slide the pieces into place. Not satisfactory – I F**KED around with this stupid spreader bar for ages – more hours than I wish to count. THERE IS A BETTER WAY! Make a spreader bar - Get approx. 3-4’ of 1/2” EMT electrical conduit and 18-24” of 1/2” threaded rod with a nut. You will also need some small, approx. ¾” thick hardwood blocks to protect both the forward and aft spar.
  • After placing whatever hardwood block you’re going to use against the forward side of the aft spar, insert your EMT tube through the access hole where the loose end of the spreader is, and place it against the aft wood block. Using the aft spar inspection hole it should be easy to see the EMT tube up against the wooden block. You should then mark the cut point on the tube such that approx. 1-1.5” of the tube is visible through the insertion inspection hole. Next take the tube out and cut squarely at the mark. Now you insert your threaded rod and nut and then insert the assembly back into the wing, making sure the aft end of the tube is resting firmly against the wooden block (which should be sitting against the forward face of the aft spar.) Next place a wooden block against the aft face of the front spar and start turning the nut using a ¾ open ended wrench to extent the spreader bar such the threaded end also sits snugly against the forward wooden block. (In the pictures, you will notice my threaded rod has a saddle on on – this is because I re-appropriated a piece of threaded rod from a PA30 bungee tool.) You can now exert enough spreading pressure against the forward and aft spars to easily place the spreader bar and drag wire attach plate back in place and insert the retaining bolt.
  • Torque – the bolts are held in shear – the Service Letter mentions standard torque found in AC43.13 however given the torque required to remove the nuts from the through-bolts holding the wing strut attach plates in place, I strongly suspect the factory is using maximum allowable torque for each bolt rather than shear or tension torques.
  • Once the spreader back in place and the remaining bolts are reinstalled, safety wire the spreader bar bolt utilizing .041 brass safety wire.
  • Next job is to re-tension the drag wires. This is where the 5/32” wrench will come in handy as there is considerable tension on the drag wires.
  • With the wing-strut attach plates back in place the rest of the re-assembly is simply a reversal of the disassembly procedure. It’s worth having a tube of torque seal or witness paint to mark fasteners upon reassembly.
 

Attachments

Bob Turner

Well-known member
Joined
Apr 4, 2018
Messages
759
Any idea what percentage of these fittings are failing inspection? I have seen badly corroded fittings - internal corrosion!

Why do you have to level the aircraft? Does your wing support not work in the 3 point attitude?
 

Handysmurf

New member
Joined
Jan 11, 2020
Messages
4
Any idea what percentage of these fittings are failing inspection? I have seen badly corroded fittings - internal corrosion!

Why do you have to level the aircraft? Does your wing support not work in the 3 point attitude?
Bob, of course the wing trestle would work - but I would not want to risk the wing/aircraft sliding off the trestle. That's an awful lot of weight, unsupported - remember the wing tanks were close to full with long range tanks.