Fuel tank sump drain

[Brian2034]

Yes, plenty of discussion on the topic.

My C has the original fuel drains and yes we had a issue with one not sealing on its maiden and only flight in 10 years back to her new home.

The drain did eventually stop leaking during the flight but it doesn’t make sense to have non-serviceable fuel drains.

Iv’ve read through the service bulletin M20-188A and have a couple question. 
The wing nut used for the replacement drain is just a standard wing nut with a groove machined across the mounting plate, does anyone have the original wing nut part number not the modified wing nut part number. 
Has there been an alternative or newer method devised for the fuel sump drains other than the service bulletin.

 

 

[Jsno]

I had to change one of the nut plates.  I just bit the bullet and bought from Laser because I could not find anything else.  

[Brian2034]

Fuel drain nut plate unmodified

MS21078-7  

7/16 -20 thread size

$35

 

[47U]

On 1/20/2025 at 2:29 PM, Brian2034 said:

Has there been an alternative or newer method devised for the fuel sump drains other than the service bulletin.

The LASAR version… .2 amu.  It looks a lot more robust than the standard MS nutplate.  Might be cheaper in the long run, if not for you then a future owner.

[Brian2034]

I did see that one on the Lasar site, definitely more robust and a better option than a standard nut plate with a groove. 
 

 

[N201MKTurbo]

13 hours ago, 47U said:

The LASAR version… .2 amu.  It looks a lot more robust than the standard MS nutplate.  Might be cheaper in the long run, if not for you then a future owner.

Are they using screws and nuts on that one? It looks kind of long to rivet.

[65MooneyPilot]

I think this is what you are looking for. I guess you did not want to be extorted for a simple nut plate. The block looks better for almost the same price. 

[Brian2034]

8 hours ago, N201MKTurbo said:

Are they using screws and nuts on that one? It looks kind of long to rivet.

That was my next question is that block secured with screws and nuts or extra long rivets?

They may be threaded for screws?
There a Mooney item someone must have installed a set of them. 

 

 

 

[47U]

13 hours ago, N201MKTurbo said:

Are they using screws and nuts on that one? It looks kind of long to rivet.

I’m not a sheet metal guy.

Aircraft Spruce lists an 1/8” structural rivet a full inch long.  I think that would cover it.

AN470AD-4-16

Then again, as my sheet metal troops used to tell me, a bolt will replace a rivet according to T.O. 1-1A-8.  

[N201MKTurbo]

It always amuses me when I open a tank and see that nut plate slathered with sealant. The only leak point is through the rivets. Even sealing the shop heads is worthless. You need to seal the bottom surface and the rivets. Once the tank is opened up, it only takes a few minutes to drill out the rivets, clean up the nut plate and buck the rivets back in. The bottom surface needs to be sealed and the rivets need to be bucked wet with sealent.

[47U]

6 minutes ago, N201MKTurbo said:

The bottom surface needs to be sealed and the rivets need to be bucked wet with sealent.

Anything wet with fuel or through a pressurized structure was installed wet with sealant.

[N201MKTurbo]

29 minutes ago, 47U said:

Anything wet with fuel or through a pressurized structure was installed wet with sealant.

Should be. Doesn’t mean it was.