Corrosion inspection during pre-buy?

[FlyingAggie]

My pre-buy inspection of the M20K is coming up in a couple of weeks at LASAR.  In LASAR's standard pre-buy they normally don't pull the wings bolts to gain access so they can run a magnet down the inside of the fuselage steel tubes to look for corrosion.

LASAR's rationale is they will remove the left side interior panel and inspect for corrosion on the exterior of the steel tubes and will stop there if all is clean.   If they find external corrosion, they will then inspect the insides.  Is this a good strategy?

Should I insist (and pay extra) to have the internal inspection performed?

[Kwixdraw]

Laser is very experienced and I would trust their opinion on the best way to inspect.  If you get a chance to see the tubing after the panel is removed look at the screw head where they hold the skin mounting plates to the tube structure. The screws will give you a good clue as to how much moisture they have been exposed to. They can look a little like they have powder lightly sprinkled on them without too much concern but it they look erroded at all I would want to check inside the tubing for water and rust. Just my free $.02 worth. 

[airkraft]

Alan, I'd also look at where the aircraft has been in making my decision on whether to inspect more thoroughly.   Hangered in Tucson  or tied down outside in Houston?

[FlyingAggie]

Aircraft has been tied down outside for last four years in the bay area.  Before that it was in the midwest.

 

Alan

[airkraft]

Canopy cover, at least, I hope. Certainly not ideal storage conditions.  Like the others have said, communicate with Lasar.  They know what they are doing... GK

[Kwixdraw]

Keep in mind that there are some who think that a cover is not a good thing to keep on in wet weather as the canvas can hold water against the window/skin junction and in their view allow longer for the water to seep past the sealant of the windows.

One other thing I might mention is that just pulling one panel is no guarantee that another area didn't have a leak that allowed a lot of water through. It is a calculated risk no matter how you approach it if you don't do a full 208B inspection. You might look over the log books and see when or if the 208B was done and who did it. My J had the 208B signed off but it still had the old insulation in it. I guess that would technically make it a 208A wouldn't it?

[FlyingAggie]

Isn't SB208A the inspection and SB208 the remediation.  I see the entry for both in the logs.

Alan

[RJBrown]

Corrosion never sleeps. Even if it was checked you need to know it is OK today.  There is no remediation, no permanent fix. The SB replaces (Correct me if I am wrong) insulation that held moisture with insulation that doesn't. This helps fight future corrosion but wont stop it. One reason both my planes were always based here in Colorado.

[Kwixdraw]

Yes I believe that is the case that 208a is the "Kerrville, we have a problem" inspection and 208b is the "fix". Everyone calls it the 208b because they are lumped together in 208b. Like I said, mine was signed off for both but the insulation was the old type. How well was the inspection done? Well I wasn't sure but I was reassured by the prebuy inspector that there was no sign of water entry and it is Southern Calif. 40 miles inland so no big worry. I did redo the inspection later and it was OK. I am in the process of doing it again since the plane has been tied down outside for quite some time.  Exactly correct that corrosion never sleeps. My hangar seems to be damp inside, though no visible moisture is found. I find my polished tools get a bit of rust on them or fingerprints if not wiped down with RIG between uses. It only takes a week or so to develop. Im not sure if it's because of our recent rains with water building up to the edge of the hangar floor or what but it's something I have noticed and will take precautions against with both the tools and the aircraft.

[FlyingAggie]

RJ,

What is your other plane?

Alan

Quote: RJBrown

Corrosion never sleeps. Even if it was checked you need to know it is OK today.  There is no remediation, no permanent fix. The SB replaces (Correct me if I am wrong) insulation that held moisture with insulation that doesn't. This helps fight future corrosion but wont stop it. One reason both my planes were always based here in Colorado.

[Skybrd]

Quote: pmccand

I've heard about this corrosion inspection and sometimes having to pull the wing for repairs. One of my friends had that happen to his Mooney. I wonder if there has ever been a inflight structure failure due to corroded tubes. Is this an manditory AD inspection or a suggestion service bulletin. -- Years ago I pulled a wing off a wrecked 1967 M20C Mooney so it could be transported and it was big job (N2901L). Hope my recent purchased Mooney won't have to have it done.

Inspecting with magnet is standard operating procedure the LASAR guys really know their Mooney's.  I'd trust their advice.  Also you might want to consider asking them about checking the wall thickness of the tubes, but that is really cost prohibitive in my opinion.

Corrosion is a REAL BAD problem on Mooneys. I just bought a B model and wound up replacing three major tubes in the area you are referring to.  When I bought the m20b, all we did was a visual inspection of the outside of the tubes.  Big mistake.  Corrosion was extensive and severe.  The corrosion starts from the inside and works out. The primer hid most of the damage. Even  a little corrosion is bad because the tubes are only 0.025" thick and a little corrosion in this area can cause significant strength reduction.  I dont mind buying a corroded bird, but then again,  I can work on the bird myself (with the assistance of my IA).  I shudder to think how much it would cost to PAY someone to do the work for me.

Phil Mc

[fantom]

 

[KLRDMD]

Quote

>: Skybrd