Landing gear hardware and tail wheel rigging

aftCG

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Apr 3, 2018
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526
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Tacoma, WA
I mentioned my landing gear in my introduction but thought it might be better to create a thread in the tech section where it might be of use to someone.

Shortly after buying my plane I joined the Bellanca group and read up on the failure of the bent U-bolt type of main landing gear hardware and how the factory recommended replacement of the old type with the newer style which resembles a piece of flat bar stock with two holes, and inspection of the bolts every 500 hours.

I wasn't sure what type of hardware I had, and the logs showed them last being replaced in 1988. Given my desire to land on many unpaved runways and to possibly provide some flight instruction in my plane I decided that it would be good piece of mind to include the upgrade and replacing all the hardware.

I was also experiencing tail wheel shimmy on some landings and using the ACA publication showing how the pivot axis should be aligned it was clear my tail wheel leaf springs had sagged.

Main gear first
Here's a link to the Aircraft Spruce catalog page showing the hardware set up:
https://www.aircraftspruce.com/catalog/lgpages/lghardware.php?PANEL=325
I have previously read where people thought the bolts were ACA only. Those are MS bolts and not from ACA, but I should warn that the bolts are $29.50 each (!).
The Q&A section has a question from a customer asking if the bolts are included in the new configuration and they are told "no". That turns out to be false information. The $177 price (as of this writing) includes the bolts but not washers or nuts. I was able to return my extra four bolts and then cough up for $21.85 each on the nuts. Rumors of that price including dinner and a movie are exaggerated.
IMG_20180427_113140.jpg
Maybe like me you aren't sure if you have the upgraded style. Fear not, because the flat bar and bolt heads are clearly visible from outside the plane. Getting to the inboard, single bolt location on each leg required my mechanic to put a small inspection cover in the fabric. They are hardly noticeable.


Moving to the tail
Here is one I thought would be easy. I had carefully examined the back of the plane looking for the reasons why my tail wheel was sagging a bit and the only anomaly I found was that I had no rubber pad (as shown in the parts manual). In place of it was a small wedge, compensating for the fact that it leans off to one side when viewed from the back. I'm quite sure I stumbled across others having reported this issue when looking in the Bellanca Citabria forum archives but can't find it now.

It occurred to me that the reason we get this is because of that boot full of right rudder we hold before the tail comes up. We think we're zeroing out the forces but we are obviously not. I had assumed that the leaf springs had not only sagged, but had twisted too. I was sure it would all be corrected by new leaf springs.

Only it wasn't
My mechanic installed the pile of new bits and the tail wheel leans just like there should be a wedge in there. It is worth noting that the factory has also replaced the small bent U-bolt design on the tail wheel with a smaller cousin of the bar stock + two bolts used on the main gear. I had obtained the old style from Wag or Spruce before I knew that.

My mechanic said he was going to call ACA and I ended up doing the same because I knew he was busy and not sure when he would get around to it. First I'm going to say the factory is just as nice as anyone has ever said. They do not stand to make a million dollars from my 53 year old aircraft and yet they took my call.

The short version is that there is no ACA approved fix or kit of parts for this condition. He alluded to the fact that Aeronca, Bellanca and ACA have not been on the same page about several issues without specifying that this was one of them. He did offer suggestions as to where we could find problems. Bent aircraft is one (it's not), broken rudder post right below the lower hinge (great place to look but also not my problem). If you get down and really grovel around under the back of the plane it appears that the metal plate with the ears was welded on slightly crooked (and our evil friend trigonometry exaggerates the effect). The factory suggestion was that minor rigging problems could be worked around by torquing one side a bit tighter, squishing the rubber pad. We would need to crush one edge of the rubber completely flat to achieve alignment that way

The current plan is to use the same wedge, and when I get around to stripping the fabric off this is one of those things that can be made perfect.
 
Last edited:

Citabria.pt

Active member
Joined
Mar 30, 2018
Messages
33
Location
LPSR - Santarém - PORTUGAL
I finally worked out my 2018-shimmy issue today, on my '69 7ECA S/N 661.
It took a new set of leaf springs from ACA. These new ones are 1-¾ width, and the previous ones on older 7ECA's are 1-½.
And the new bar with 2 bolts to replace the old 1-½ kinda U-bolt.
And a new pad, and a new leafs-to-scott thru-bolt.
They fit nicely on the existing metal plate with ears below the Rudder post. And that plate is aligned with the plane, so it was a clean fit.
The tailwheel's "king-pin" was only slightly forward of previous leafs, but these new ones are slightly stiffer. Guess old ones were too tired anyway, as I previously have col-re-bended them 3 times.
Anyway, went flying and shimmy issue diminished, but was not off completely.
Next culprit was the internal V-shaped spring that locks & unlocks the tailwheel. Figure 23 on Alaskan parts for ABI-3200. It had serious dents from the unlocking pad, and guess it wasn't stiff enough due too much 360º shimmy-all-around issued, and 3 or 4 re-bendings.
New internal V-shaped spring changed for a new one bought on Spruce. Noticed the new one was a little thicker, and definitely stronger, yet allowing the 2 rectangular spacers to be installed with some gentle force, to to break anything expensive (tailwheel fork!). It was a nightmare to install the pin #26 on Alaskan parts drawing, but after 2 hours finally managed to.
No more internal play between the fork and the steering arm. Even sharped the edge where the V-shape spring works on the steering arm with an ignition file. Everything's nicely fit now.
Test flight it, with intentionally touchdown with rudder applied. Previously it was the start of 2 or 3 360º turns of the tailwheel. Now it might just swivel 10 or 20 degrees, and self-dampens that swivel. SHIMMY NO MORE !!!
Leaf springs might be the main culprit for the WRONG geometry of the "king-pin", but beware of any dents and plays of your V-shaped spring.
Mine was just unlocking too easily, allowing the wheel to rotate 360º a couple of times before settle down and stop shimmy.

Hope it helps someone.
Have fun.
 

Bob Turner

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Apr 4, 2018
Messages
2,826
I missed this one.

Of interest - maybe critically so - the MS bolts require special washers under the head.

The original AN bolts should be replaced with MS bolts, especially the inner bolts. Then, apparently no more 50 hour re- torque.

On the price: four years ago ACA wanted $130 each for the longer bolts for aluminum gear legs. I got them from Genuine for $28. Washers and nuts, while expensive, were nowhere near ten bucks each - I could check, but I think it was closer to three bucks.

The cross bar may be radiused for the MS bolts - I will check mine - but if it isn’t, replace the now damaged bolts and always use the MS washers.
 

Bob Turner

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Joined
Apr 4, 2018
Messages
2,826
Apparently the new outer bars are radiused for the MS bolts. You absolutely need the special washers for the two inner attach bolts.

The guy who started Genuine taught me a lot about bolts, and sadly he only got several hundred dollars of my business. It is now run for profit only - they do not care what your bolt requirements are; you are free to order from stock.

The original guy saved me thousands of dollars by selling me oversize AN bolts. The alternative was a new tail cone on a C-180. You cannot buy oversize bolts any more.
 

Big Ed

N50247 - '79 Super D
Joined
Jul 20, 2020
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Location
Tampa, FL
Here is the kit I just got from ACA. It goes on the plane today. Pricey, but the consequences of failure are significant. The jack adapters were not part of the kit, but well worth the $50 each IMO and easy to justify for a plane I plan to own for the next 20 years.

PXL_20210220_004254761.jpg

Here is a closer look at some of the components. Note the fillet between the internal wrenching bolt head and shaft. Also note the beveled inside edge of the through-hole on the bar, and the beveled washer, both to accommodate the bolt head fillet.

PXL_20210306_162353288.jpg
 

Bruce

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Dec 22, 2018
Messages
439
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Knoxville TN
Did they provide a new torque numbers with the flat bar or just use the old numbers from original u bolts?
 

Big Ed

N50247 - '79 Super D
Joined
Jul 20, 2020
Messages
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Location
Tampa, FL
Did they provide a new torque numbers with the flat bar or just use the old numbers from original u bolts?
Use the old numbers from the table in Service Letter C-135, according to ACA.