70s-era nose gear door linkage hardware

[Vance Harral]

In the midst of the fuel selector debacle described in my other thread, either myself or the adult supervisor in the shop have disconnected and reconnected the port side nose gear door linkage about a half dozen times (this makes it possible to get to the screws on the tunnel panel which must be removed to access the fuel selector, without jacking the aircraft and retracting the gear).  In the midst of this, I realized the connecting hardware installed in our airplane is not what's called out in our parts manual.  It's been that way for years, is functional, and I'm not particularly concerned about it, but it's a curious mystery.

The aircraft is a 1976 M20F, but the parts manual is applicable to C/E/F/G models from 1968-76, and there are no model-specific notes.  Wondering if other owners in this age range might comment and/or post pics.

First, I quote from that bible: Figure 26, item #23:

 

 

As I read this, I'd say the connecting hardware should be assembled from fore to aft as:

    AN23-21A bolt -> forward gear door bracket -> ( some combination/order of 4 Mooney-specific P/N spacers and the rod end) -> aft gear door bracket -> AN960-10 washer, AN365-1032 nut.

What we have is decidedly different.  I forgot to snap a photo yesterday, but on the starboard side ours is like:

    AN23-22A bolt (slightly longer than spec) -> forward gear door bracket -> thin washer -> spacer -> rod end -> spacer -> thin washer -> AN960-10 washer, AN365-1032 nut.

This assembly does not meet the "rule" that you should be able to see at least one thread of the bolt extending past the nut, even in spite of the longer bolt being installed.  I'm not too freaked out about it because it's very close - the end of the bolt is flush with the end of the nut.  It's possible if I cranked down the nut I could see a thread, but that would take it way past torque spec and seems like a bad idea.

On the port side, the assembly is similar, except instead of an AN23 bolt, there is some sort of 10-32 machine screw installed instead, with a flat screw head.  One hopes it's an aircraft-grade machine screw, but who knows?  Whatever it's other failings may be, it's long enough that a couple of threads extend past the AN365-1032 nut when appropriately torqued.

At first I thought this whole mess might be a ham-fisted attempt to replace misplaced Mooney-specific spacers at some point in the past.  If you Google that 550017-005 part number, you'll see some ebay and salvage listings with fairly silly prices (like $20 apiece).  But the pictures in this eBay listing look like the spacers we have, so I think there's a good chance we have the correct equipment there.

I have no idea when/why the "extra" thin washers were added our assembly, but I can tell you there is a little slop in the assembly without them.  That slop could be corrected by bending the gear door bracket slightly, and if we did so, I suspect the correct-size AN23-21A bolt would receive a nut on the tail end with a thread showing.  This is my tentative course of action/direction to our mechanic, but I'm not sure we want to go bending on the gear door bracket.  God only knows what it would cost to fix if it cracked, and of course I'm gun-shy after the fuel selector incident.

As for the machine screw, who knows where it came from?  But the head on that machine screw is more svelte than a conventional AN bolt, and you always wonder about clearances inside the gear wells.  Maybe I missed a Service Bulletin indicating replacement of the AN bolt with a machine screw?

Anyway... all this is a long-winded way of asking other vintage Mooney owners what kind of hardware they have.  Comments welcome.

Edited May 28, 2020 by Vance Harral

[cferr59]

I just had my 1965 apart and it is set up as follows:

AN type Bolt --> Bracket --> thin spacer  --> rod end -->  thick spacer -->  Bracket --> Washer --> Washer --> Nut

Both sides have AN type bolts, not machine screws and are set up the same way.  I believe the thick spacer is the 550017-005 part. I have no idea what part the thin spacer is.

[Vance Harral]

Thanks for the data point, cferr59.  I don't see any justification in the parts manual for having differently-sized spacers and two washers between the bracket and the nut.  But yours is certainly no stranger than mine.

I'll hazard a guess that nose gear door brackets get bent in or out a little over time, and some mechanics periodically change bolts and/or add/remove various washers during annual inspections to eliminate slop.  Perhaps there is justification for this in AC43-13 as  a "standard practice", but I'm not an A&P.

I suppose it's even possible this sort of substitution was done at the factory, as various hand-built nose gear doors rolled off the production line - I know there are other places in my parts manual that say things like "spacers as required".

[carusoam]

You guys have done the homework!

If you need more details, the doc (M20Doc) can probably fill in the last bits...

Best regards,

-a-

[Vance Harral]

One bump of this thread, since it's the weekend, and I'm hoping a few folks might be out flying and able to snap a quick photo.