How much corrosion is acceptable for a preflight?

[aviategw]

While preflighting an Archer for an instrument training flight, I noticed some obvious rust and bubbling paint at the juncture of the trailing edge of the wings and the fuselage. I had to lower the flaps to see the area I was concerned about, but once I did, I got an unobstructed view of a mess. The plane had obviously been recently painted, and looked great. However, when I looked at this rust, I was concerned. From my days in auto shop class, I think that seeing bubbling paint and rust on the outside of a surface would indicate the possibility of rust and corrosion on the inside of the surface, out of view. My concern is with structural integrity. Most of my time is with high wing Cessnas, where I've never seen this kind of corrosion. (Not any causal relationship between a Piper A/C and rust, just an observation.)

Any one have any thoughts on this kind of thing? Am I just being too conservative?


G

[Doug Taylor]

It would concern the heck out of me! But I'm probably not a very good source.

[USMCmech]

[ QUOTE ]
While preflighting an Archer for an instrument training flight, I noticed some obvious rust and bubbling paint at the juncture of the trailing edge of the wings and the fuselage. I had to lower the flaps to see the area I was concerned about, but once I did, I got an unobstructed view of a mess. The plane had obviously been recently painted, and looked great. However, when I looked at this rust, I was concerned. From my days in auto shop class, I think that seeing bubbling paint and rust on the outside of a surface would indicate the possibility of rust and corrosion on the inside of the surface, out of view. My concern is with structural integrity. Most of my time is with high wing Cessnas, where I've never seen this kind of corrosion. (Not any causal relationship between a Piper A/C and rust, just an observation.)

[/ QUOTE ]

Ruel # 1 Aluminum doesn't rust, only Iorn/Steel does.

Rule # 2 corrosion anywhere on an aircraft is serious concern that should be addressed imeadiatly.

Rule # 3 the skin of an aircraft is made of AL, the rivets are Steel

What you described could be Exfoliation where the corrosion inside the grains of the metal has reached a point where it will start to flake off. This is very serious. Not because of what you can see, but because of what you can't (the spar, hinges, control rods, ect.)

This airplane needs to be looked at imeadiatly by a mechanic. Specificaly ask the owner to let you know what they find out. If they don't, I would wonder about wether they fixed it or not. At the very least the paint should be removed in that area, it should be inspected throughly, and repainted.

The new paint job is puzeling. A good paint job involves striping all the paint off down to the bare metal. Any corrosion can be seen and removed. A cheap paint job may be a skuff and spray. Where the new paint is applyed over the old, this may have hidden any corrosion.

[aviategw]

I'm probably being a bit conservative, but it troubled me. The surface wasn't smooth, but rather porous and abrasive. I don't really know if rust is the right technical term, but it was definately not right. It was on both wings, and it was in the recessed area where the flaps retract when they are at 0 degrees. It was an area of appoximately 8-9 inches wide and was quite discolored.


I wrote up a maintenance discrepancy on the airplane, I'm interested in seeing what is done about it.

I noticed this on the preflight, but as this plane was the only one at the school that had the Garmin 430, which I need to learn, I was overly motivated to go fly. I got more and more uncomfortable as the flight progressed and the sky got bumpy. During the postflight, I took a few extra minutes to look at the wings. I think now that I would not fly this plane again until this issue is addressed.

Kinda a bummer, because the plane flew great, and I got some good time in on the 430 before I tackle the ATP Seminole next week.

[DE727UPS]

You could talk to the mechanic who did the last 100 hour and see if he's aware of it and what his take on it is. If he refuses to discuss it with you or won't come out and look at it with you.....I'd find another place to fly.

If the mechanic is aware of the problem and doesn't feel it an immediate concern, you are basically ignoring his opinion if you decide the plane is unsafe. If you refuse to fly the plane, that's your business.

You could also contact the nearest FSDO, ask for a maintence inspector, give him the location and tail number, and see if they are interested in checking it out. This won't make you any freinds at the FBO but would give you another opinion.

[USMCmech]

[ QUOTE ]
I'm probably being a bit conservative, but it troubled me.

[/ QUOTE ]

The fact that it was bad enough that your untrained eye saw it tell me that it is probably pretty bad. Corrosion takes time to develop and it should have been seen by a mechanic on it's last 100 hr.