M20F Pictures Requested

[Stephen]

Hi Guys, I wonder for those of you who have an "F" model  if I could get a picture of the clearance (on your aircraft) between the castle nut pictured and the tube where you can see paint flaked off on mine. Both left and right landing gear on my 1969 aircraft seem like the parts (bolt /castle nut and the tube structure) are touching. Now I'm wondering if this is:

 

1) Normal ( don't think so but Google imaging Mooney M20F > Images produces pretty much useless comparison cases

2) A typical wear patter that needs can occur over time due to wear/landing stress

In addition to getting some photos for comparison (a few different angles would be greatly appreciated!!) my thoughts are if I have the issue (and if it needs priority maintenance correction) I might tip others off to look out for this. 

 

Kind regards and appreciated as always

 

Stephen

Rogers, AR

[Shadrach]

Hi Stephen,

I cut this pic out of a Gear preload pp presentation I put together for someone.  The next time I am at the airport I'll try and get it from an angle that better shows the clearance. There is not a lot of clearance between the nut and the tube but yours appears to have no clearance.

 

[Stephen]

Thanks Shadrach!

 

[RLCarter]

No pictures, but on my E there might be 0.060" or so, it's damn close and if the bushings are worn it would hit

[XXX]

Stephen,

I found this pic, but can get a better one tomorrow. It doesn't appear that they touch. I had the gear powder coated last annual (a year ago) and it would show if there was any contact. 

[carusoam]

Put that photo in the contest for cleanest undercarriage!  

Nice work, Chupa!

Best regards,

-a-

Edited March 9, 2017 by carusoam

[XXX]

Ok Stephen, here you go...

A, forgive the grease, we're in the middle of my annual.

Steve

[Stephen]

Thanks Chupa!  So both of mine are touching you have a few paper sheets worth of positive clearance. I'm gong to put my plane up on jacks this weekend to carefully shake the gear to check for looseness. Curious if anyone else has run into this issue or has the issue on their aircraft..... 

[gsxrpilot]

The value of MooneySpace on display again!

[Vance Harral]

I don't have a photo handy, but for what it's worth, our gear have roughly zero clearance there (can see a bit of the paint rubbed off).  I've wondered about this too.

[Yetti]

Left side and right side.... I would be concerned if I found them to be rubbing.  The grease/dirt is there to help me better spot if they are rubbing. :-)

 

[Stephen]

WOW Yetti, you have TONS of space; I think I now have clearance envy.   I called Don Maxwell and he said to look at bushings and shims on the "baby shoe" (attache point for the forked rod that has the castle nut in question on it). Roger on the grease interference tripwire indicator / corrosion proofing. It may have something to do with why your bushings are apparently in great shape. 

[gsxrpilot]

Just swing by DMax and let him sort those Baby Shoes out for you.

[Stephen]

I'm grounded with CIES going in and JPI unable to give me an ETA on shipping the EDM 900

[Stephen]

On 3/9/2017 at 11:49 AM, Vance Harral said:

I don't have a photo handy, but for what it's worth, our gear have roughly zero clearance there (can see a bit of the paint rubbed off).  I've wondered about this too.

Yes, I think this is something to lookout; I'll pirep the fix process. I think it is either bushings or shimming (per DMAX) that we both need squared away. 

[Stephen]

Updated ship date from 'Spruce is 3/24 for the EDM 900

[Vance Harral]

@Stephen, any chance you (or anyone else) could provide a PIREP on the work to fix the clearance issue on these retraction links?  Our annual is coming up in February, and I'd like to address our clearance problem.  I have a couple of questions about this I'm hoping to research in advance, as opposed to myself and the A&P just diving in uninformed.

First, based on looking at my Parts Manual, any/all of the following seem like they could be involved:

    * ref -010 bolt AN26-17
    * ref -010 washer AN960-616
    * ref -010 nut AN320-6
    * ref -010 cotter AN380-3-3
    * ref -010 bushing 914020-017 (Mooney P/N, listed at LASAR for $36.00)
    * ref -011 bolt AN6-22A
    * ref -011 washer AN960-616
    * ref -011 nut AN365-624
    * ref -011 bushing 914020-017 (Mooney P/N listed at LASAR for $36.00)
    * ref -014 spacer p/n THRU-015 (weird P/N, what is this?)
    * ref -014 bolt p/n "as-required" of AN5H<various_sizes> (WTF???)
    * ref -014 bushing p/n 914020-18 (Mooney P/N, can't find in searches)

Any comments on what actually needs to be replaced? Most of the above is standard, inexpensive AN hardware, but there are a couple of Mooney-specific part numbers, a "THRU-015 spacer" (is this just a washer?), and an "as required" size of bolt that I don't understand.

Second, any comments on the procedure(s) to R&R the hardware?  The section in my Maintenance Manual on landing gear discusses R&R of the landing gear themselves, as well as rigging, but I can't find any procedures describing service of the bolts/bushings/washers/nuts associated with the retraction links.  I'm hoping it's as simple as running the gear halfway up to relieve tension, then just straightforward wrenching, but hard to say without having done it before.  Any tips would be appreciated.

[Stephen]

We adjusted the shim under the “baby shoe” so that they barely clear, the A&P that did it said that they should have positive clearance when not on the ground but I’ll look when we get it jacked up (my annual is supposed to start Monday).

[jetdriven]

I would be very concerned about the hardware scraping the tube. In absence of any other guidance, you only get 10% of material thickness before the part is ruined, which is only about a .010-.020" scratch.  not very much at all.

[Vance Harral]

3 hours ago, Stephen said:

We adjusted the shim under the “baby shoe” so that they barely clear, the A&P that did it said that they should have positive clearance when not on the ground but I’ll look when we get it jacked up (my annual is supposed to start Monday).

Thanks for the reply, Stephen.  I'm not sure I understand what people mean when they refer to the "baby shoe".  Is it the trapezoid-shaped part of the truss, where the bolt and nut of concern run through?  i.e. the part outlined in red below?  I guess it does look sorta like a baby shoe.

If that's what we're talking about, I'm having a difficult time understanding what shims are there, and how they could be "adjusted".  Looks to me like a simple bolt/bushing/nut arrangement.  I think people sometimes use the word "shim" where I'd just say "washer", and I'm aware there are different thicknesses.  Are we just talking about inserting more/different washers?  Maybe an oversized bolt?  I'm wondering if that's what the parts manual means by these callouts:

    * ref -014 spacer p/n THRU-015
    * ref -014 bolt p/n "as-required" of AN5H<various_sizes>

I do want to do something about this at the annual.  Ours starts in about a week, would be glad to share experiences with you.  For what it's worth, I'm not particularly comforted by the idea there might be more clearance with the weight off the wheels.  That would just mean every takeoff and landing generates an additional scraping event.  As jetdriven points out, it doesn't take much rubbing to damage the landing gear truss.

Anyway, thanks much for the info, and for taking the time to respond.  I plan to give LASAR a call Monday morning to discuss further, but would appreciate any additional comments here.

[cbarnes403]

Here is a great web site on aircraft hardware, do a search for spacers or go to page 157.

https://www.askbob.aero/sites/default/files/Genuine_Aircraft_Hardware_Catalog.pdf

 

[Stephen]

On 1/27/2018 at 9:56 AM, Vance Harral said:

Thanks for the reply, Stephen.  I'm not sure I understand what people mean when they refer to the "baby shoe".  Is it the trapezoid-shaped part of the truss, where the bolt and nut of concern run through?  i.e. the part outlined in red below?  I guess it does look sorta like a baby shoe.

If that's what we're talking about, I'm having a difficult time understanding what shims are there, and how they could be "adjusted".  Looks to me like a simple bolt/bushing/nut arrangement.  I think people sometimes use the word "shim" where I'd just say "washer", and I'm aware there are different thicknesses.  Are we just talking about inserting more/different washers?  Maybe an oversized bolt?  I'm wondering if that's what the parts manual means by these callouts:

    * ref -014 spacer p/n THRU-015
    * ref -014 bolt p/n "as-required" of AN5H<various_sizes>

I do want to do something about this at the annual.  Ours starts in about a week, would be glad to share experiences with you.  For what it's worth, I'm not particularly comforted by the idea there might be more clearance with the weight off the wheels.  That would just mean every takeoff and landing generates an additional scraping event.  As jetdriven points out, it doesn't take much rubbing to damage the landing gear truss.

Anyway, thanks much for the info, and for taking the time to respond.  I plan to give LASAR a call Monday morning to discuss further, but would appreciate any additional comments here.

The baby shoe is this thing:

   if you look at it in your wheel well it looks kind of like a baby shoe. 

It is part "13" in the series below.

 

[Stephen]

"... For what it's worth, I'm not particularly comforted by the idea there might be more clearance with the weight off the wheels.  That would just mean every takeoff and landing generates an additional scraping event.  As jetdriven points out, it doesn't take much rubbing to damage the landing gear truss...."

Agreed, needs solved. 

[Vance Harral]

Thanks, Stephen, that's very helpful.  I had been looking at the "Gear Retraction System" diagram in my parts manual, rather than the "Main Gear Assembly & Installation" diagram.  Both of those diagrams show the triangular truss piece (item #12 in your photo above), but only the latter shows the "baby shoe" and the fasteners that pass through it.

In looking closely at the diagram, it appears to me the wear items are the fastener assemblies labeled #10 and #14.  The callout for reference -014 is complicated, however, as I mentioned above.  It lists 5 different lengths of AN5H bolt with an "as required" note, as well as a "THRU-015" spacer.

Looking at your actual photo above as opposed to the diagram, it does appear that there's a spacer of some sort between the #13 and #15 parts.  I'm guessing this is the mysterious "THRU-015" spacer, but that sounds like some sort of custom part.  I can see how a thicker or greater number of spacer(s) would increase clearance, but would also require longer bolts, and I'm assuming that's why there are different bolt lengths listed.

Presumably the clearance was good when the airplane left the factory, though. If so, I'm curious whether a thicker spacer is really the correct solution.  Wondering if the problem is simply that the bushings have worn to the point where the whole assembly flexes sideways a bit when the gear moves into the locked position.  In that case, new bolts and bushings might fix the problem without changing the spacer or bolt length.

Again, I plan to call LASAR tomorrow and see what they have to say about it.  Will post info here when I have it.

 

[Stephen]

9 minutes ago, Vance Harral said:

 

Looking at your actual photo above as opposed to the diagram, it does appear that there's a spacer of some sort between the #13 and #15 parts.  I'm guessing this is the mysterious "THRU-015" spacer, but that sounds like some sort of custom part.  I can see how a thicker or greater number of spacer(s) would increase clearance, but would also require longer bolts, and I'm assuming that's why there are different bolt lengths listed. 

Agreed 

Quote

Presumably the clearance was good when the airplane left the factory, though. If so, I'm curious whether a thicker spacer is really the correct solution.  Wondering if the problem is simply that the bushings have worn to the point where the whole assembly flexes sideways a bit when the gear moves into the locked position.  In that case, new bolts and bushings might fix the problem without changing the spacer or bolt length.

I agree, would like to know what your findings are. In the past (e.g. on a piper Arrow) the process to see if & which bushings are worn, I have *securely* (4 stability points per service manual)  jacked up plane and *carefully* (very low amplitude)  shake of the gear to see if it has play in bushings. DMAX was the one that indicated that they suggest that sometimes shimming the baby shoe can be used to deal with the clearance issue.

Would be interesting (assuming bushings are tight) to see if there was a way to measure geometry at key points in gear to see if there is deflection (from a hard landing or whatever).