Flaps hardware (bolts, nuts, washers)

[Mooney-Shiner]

Hello, guys!

My 20F lives in the coastal Florida and I noticed that flap hardware is getting rusty. So I decided to shop for the replacement. My IPC calls for AN3-10A bolt, AN365-1032 nut and AN960-10L/10 washers.

I'm wondering what are the thoughts on using stainless steel hardware versions that is also available on Aircraft Spruce to get longer life without rusting?

https://www.aircraftspruce.com/catalog/pnpages/AN3C-10A.php

https://www.aircraftspruce.com/catalog/hapages/an365_2.php?clickkey=12674

[47U]

2 hours ago, Mooney-Shiner said:

I'm wondering what are the thoughts on using stainless steel hardware versions that is also available on Aircraft Spruce to get longer life without rusting?

Mooney addresses corrosion on the outboard flap hinge when a stainless steel upstop bolt is used and recommends replacing the upstop bolt with an NAS 428-3-7.  Replacing the hinge bolts with stainless might induce corrosion in the flap hinges if you’re in a high corrosion area (like Florida/coast?).  

https://mooney.com/wp-content/uploads/2020/12/SBM20-186A.pdf

[Mooney-Shiner]

21 minutes ago, 47U said:

Mooney addresses corrosion on the outboard flap hinge when a stainless steel upstop bolt is used and recommends replacing the upstop bolt with an NAS 428-3-7.  Replacing the hinge bolts with stainless might induce corrosion in the flap hinges if you’re in a high corrosion area (like Florida/coast?).  

https://mooney.com/wp-content/uploads/2020/12/SBM20-186A.pdf

Excellent! Thank you. I will inspect my upstop bolt. So I'm assuming since Mooney looks down upon using the stainless steel upstop bolt to prevent galvanic corrosion with aluminum hinge, same applies to other flap hinge hardware. I guess I will go with cad-plated hardware.  

[cliffy]

On 5/3/2025 at 11:23 AM, Mooney-Shiner said:

I guess I will go with cad-plated hardware.  

The original cad plated hardware  lasted how long?  You won't be alive when the new cad plated hardware goes bad again.

[MikeOH]

19 minutes ago, cliffy said:

The original cad plated hardware  lasted how long?  You won't be alive when the new cad plated hardware goes bad again.

Be careful to make sure you purchase true cadmium plated hardware; it is being eliminated for nearly all uses due to environmental concerns with cadmium. Aerospace is one of the few applications where it is still allowed but there are sometimes 'suitable' substitutes made that you may not want (e.g. zinc/nickel).

[Mooney-Shiner]

9 hours ago, MikeOH said:

Be careful to make sure you purchase true cadmium plated hardware; it is being eliminated for nearly all uses due to environmental concerns with cadmium. Aerospace is one of the few applications where it is still allowed but there are sometimes 'suitable' substitutes made that you may not want (e.g. zinc/nickel).

I'm getting mine on Aircraft Spruce. The description says that it is cad-platted.

 

[cliffy]

AN standard bolts and nuts both conform to cad plating requirements if true AN quality

[Mooney-Shiner]

18 hours ago, cliffy said:

AN standard bolts and nuts both conform to cad plating requirements if true AN quality

Yes, I'm definitely using AN hardware. It's cheap enough not to seek alternative in the Aviation aisle of Homey Depot.

[Mooney-Shiner]

A follow on question. I trying to figure out the configuration of the washers for the flap hinges. The Parts Manual for 67F is pretty confusing below:

The bolt/washer/nut arrangement is  confusing, so I turn to the 68F manuals for clarity:

The schematic at 68F manual made more sense. Two skinny washers on the outside of the hinge, three thick washers on the inside (2 inboard/1 outboard).

Does this look right?

 

 

[N201MKTurbo]

I would have to look at mine. It looks like you are over bending the outer bracket. Maybe putting the thick washers under the nut and bolts, and put the two thin washers on the left side of the bearings. But then why didn’t they use a thick washer instead of two thin washers. 

[Mooney-Shiner]

1 hour ago, N201MKTurbo said:

I would have to look at mine. It looks like you are over bending the outer bracket. Maybe putting the thick washers under the nut and bolts, and put the two thin washers on the left side of the bearings. But then why didn’t they use a thick washer instead of two thin washers. 

I've got pretty quick reply (within 10 minutes) from Frank Crawford. The inside block: thin L-type on the outboard, two thick washers on the inboard. Go figure. 

[N201MKTurbo]

37 minutes ago, Mooney-Shiner said:

I've got pretty quick reply (within 10 minutes) from Frank Crawford. The inside block: thin L-type on the outboard, two thick washers on the inboard. Go figure. 

Great job getting the answer on that.

[carusoam]

Great reference for Frank Crawford too!

 

Best regards,

-a-