Corrosion in frame under pilots window - M20J

[ormsbycc]

I'm in the middle of my annual and had the interior panels removed under the windows. Significant corrosion was found under the rear portion of the pilot's window (see pictures). All other areas were OK.

I need advice on what needs to be done and any possible sources for help (reasonable range from Eastern Massachusetts would be best).

Thank you,

Chuck

[Piloto]

I would call that light corrosion. Just sand it off and repaint. When reisntalling the insulation material make sure it does not cover the tubing structure. Trap moisture in the insulation material is the cause for tubing corrosion.

José

[Shadrach]

Tough to say. It looks past the point of clean up and respray in the photos, but I'm not there. The first step is to clean it up and see what you're really working with. SB M20-208 is pretty clear on what is serviceable and what is not. The SB is pretty conservative, but then your life depends on integrity of the structure...

 

NOTE: ULTRA SONIC TEST EQUIPMENT IS RECOMMENDED TO CHECK TUBE WALL THICK -NESS IF IT IS SUSPECTED OF HAVING ANY INTERIOR CORROSION. REF. FIG. SB- M20-208-2 FOR TUBE O.D. AND WALL THICKNESS: TUBE P/N MUST BE IDENTIFIED USING APPROPRIATE MOONEY ILLUSTRATED PARTS CATALOG.

10. If a tube has exterior surface corrosion that cannot be polished smooth with “00steel wool” or cannot be polished out within 10% of wall thickness in localized areas with the corrosion cumulative length not to exceed 10% of the total length of the tube, and the cumulative corrosion not to exceed 25% of the circumference of this 10% of the tube length. Refer to Figure S.B. M20- 208-2 for table of Part Numbers vs Outside Tube Diameter (O.D.)and minimum wall thickness for replacement tubes.

[Shadrach]

Quote: Piloto

I would call that light corrosion. Just sand it off and repaint. When reisntalling the insulation material make sure it does not cover the tubing structure. Trap moisture in the insulation material is the cause for tubing corrosion.

José

[ccormsby]

Thanks for the posts/info. I'm reading them all and welcome any other inputs. I'm curious why one writer says that the SB was complied with. What indicates that?  

I'm guessing it is past sanding/repainting but I hope I'm wrong. The interior condition of the tubing does concern me.

I love Mooney people calling IL my neck of the woods! I'm thinking RI, NH, CT, ME or VT!! <(;-)> Flying it there is no problem, but then getting home & flying back to get it, etc ... major hassel!!

Thanks again.

Chuck

[KSMooniac]

The foil-backed insulation is evidence of previous compliance with the SB which called for the removal of the OEM insulation that was essentially a sponge.  In your case, that is hopefully a good thing in that you likely don't have 35 years of moisture working on the steel, assuming that there was no rust present when the insulation was changed by some previous owner.  You are correct to be concerned, and you should get it addressed by assessing the overall condition of the tubes and sanding/repainting at a minimum.  If you have internal rust, then you're talking about tube replacement instead of just corrosion removal and protection.  It doesn't look terrible IMO from the pics, but only a good mechanic can make a proper determination.

The logistical challenge might be a PITA, but getting it to the right shop should be the major priority.  Taking it to a convenient shop that doesn't know what they're doing might leave you with an un-airworthy Mooney and then you'll really be stuck!  I don't know that part of the country at all, but I think Air Mods in NJ has a good reputation.

This would also be a very good time to replace the side windows (if needed) and fix the leak.  They aren't that expensive to purchase, but somewhat labor intensive.  You'll have the interior out anyway to do this work, so it is a good opportunity.

[N601RX]

The two areas with the arrow pointing to them look the most concerning to me.  I would remove the paint and clean with steel brush to get a better look.  The back side of the joint needs looking at also.  If it is rusted past the limits of SB 208 then since it is so close to the triangular joint that you might could talk to mooney or a DER and get a gusset repair approved and not have to replace the tube.  Replacing that tube would require removing the outside skin and would be expensive.

[Shadrach]

Do not, I repeat, do not use a steel brush inside your airplane!  Every steel wire that breaks off and lands on aluminum is potential for electrolysis. There are nook and crannies all over the inside of these airplanes where metal flakes can end up out of the reach of a vacuum crevice tool. Brass brush is the way to go.

[tony]

Ross, not exactly my field,  but if I understand this Mil SPEC correctly aluminum and brass are more dissimilar that steel and aluminum.

 http://www.wbdg.org/ccb/FEDMIL/std889b.pdf

 

[N601RX]

Quote: Shadrach

Do not, I repeat, do not use a steel brush inside your airplane!  Every steel wire that breaks off and lands on aluminum is potential for electrolysis. There are nook and crannies all over the inside of these airplanes where metal flakes can end up out of the reach of a vacuum crevice tool. Brass brush is the way to go.

[mooney2201]

ross just sand off corrision wipe down the tubes with mek. go get a can of zink cromate.treat the area,and go fly and enjoy your plane,from what i see its surface corrosion,dont piss your money away with some crazy idea how to fix this very simple problem,the tubes are filled with linseed oil,most people dont know that.there are plugs in the end of the steel tubes,this is done to keep corrosion from forming inside tubes.have fun save you cash,,,,,,,,,,,,,,,,,,,,,,,,

[ccormsby]

This forum is fabulous! Just want everyone to know that I am monitoring and learning from every post. I will pass this on to my mechanic and start with the brush & closely inspect advice ... not to mention reading the referenced SB.

Any other discussion/comments are also very much appreciated. When this is resolved, I will pass on my experience ... good or bad ... to repay those who took the time to post.

Thanks again,

Chuck

[N601RX]

Clean it up good and get some clear pictures. Send them to Stacey Ellis at Mooney and let them look at it.  They know the loads carried by each tube and can give you an def answer on how much is to much.  SB 208 is somewhat generic as it is a one number fits all answer.

You can search and find his e-mail on here.

[PTK]

Quote: mooney2201

ross just sand off corrision wipe down the tubes with mek. go get a can of zink cromate.treat the area,and go fly and enjoy your plane,from what i see its surface corrosion,dont piss your money away with some crazy idea how to fix this very simple problem,the tubes are filled with linseed oil,most people dont know that.there are plugs in the end of the steel tubes,this is done to keep corrosion from forming inside tubes.have fun save you cash,,,,,,,,,,,,,,,,,,,,,,,,

[Shadrach]

Quote: N601RX

This seems to go against what you said a couple of months ago.

" I've never heard or seen a single instance of galvanic corrosion. While filiform, intergranular and oxidation are all forms of corrosion that we deal with, galvanic is not one that I've seen.  Can you name me a single engine aircraft that does not have any steel in it's construction?  If AL were trying to do things on the cheap, I doubt he would have designed a fully articulating empenage... I disagree with your assesment that had anything to do with cost savings because I see no evidense that it's the case. Perhaps you've knowledge of something I don't. If so, please share."

 Cheers!

Ross

67 F

[Shadrach]

Quote: tony

Ross, not exactly my field,  but if I understand this Mil SPEC correctly aluminum and brass are more dissimilar that steel and aluminum.

 http://www.wbdg.org/ccb/FEDMIL/std889b.pdf

 

[jetdriven]

Per AC43.13 and the Mooney service bulletin you get a 10% reduction in wall thinckness.  More than that, you could replace the tubes or send in the data to Mooney and have them tell you what to do.

[M20F-1968]

The areas of corrosion are near the weld.  From the pictures this looks suspicious to be more than just surface corrosion.  First an external clean and inspect per the service bulletin is in order.  You could obtain the wall thickness of the original tubes from Mooney, or by measuring directly from a salvaged airplane with the help of your friendly salavge yard.  You could then assess the percent material lost and determine if greater than 10%.  If the tube needs to be repaired, I would contact a DAR who does welding and can repair the area himself (there is one such person at Air Salvage in Lancaster, TX).  A DER can assess structural loads and make a determination and recommendations for types of repairs (removing corrosion, then repair with overflying tube and extending weld, etc).  You may be able to get information from the structural engineer formerly with Mooney who I believe is still in Kerrville.  I believe you would need to remove to outer skin to perform any welding.

I too am in Massachusetts.  You can contact me at johnabreda@yahoo.com

John Breda

[jwilkins]

Quote: mooney2201

the tubes are filled with linseed oil,most people dont know that.,,,,,,,,,,,,,,,,,,,,,,,,

[jwilkins]

Quote: jwilkins

I think the last Mooneys that had the inside of the tubes treated with ANYTHING were either the Mooney Mites or maybe the M20A. In any case it has been a long time since any treatment was done in the tubes.

 

[jetdriven]

When I had my interior plastic out I removed quite a few screws that went into the tubes and shot plenty of LPS-3 in those holes.

[jwilkins]

Quote: jetdriven

When I had my interior plastic out I removed quite a few screws that went into the tubes and shot plenty of LPS-3 in those holes.