Surprised annual discrepancy

Ron Levy said:
:sigh: You really need to learn more about Grummans. Reading the Maintenance Manual would be a good start.
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If I dealt with them I would.

They are not very well liked in this rainy area. no one likes to open the canopy and get their seat wet.

They don't do well for what I like to do, so why mess with them.??
 
Tom-D said:
Corrosion is becoming a major problem in the aging aircraft fleet, And as I see Grumman is not exempt.
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Nobody ever said they were, but as far as the part in question is concerned, if properly cared for, it is not. What you see in the picture that started this is evidence of serious neglect, and if the airplane's been kept in annual the whole time, incompetent inspection.
 
Ron Levy said:
Nobody ever said they were, but as far as the part in question is concerned, if properly cared for, it is not. What you see in the picture that started this is evidence of serious neglect, and if the airplane's been kept in annual the whole time, incompetent inspection.
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If this is inter granular corrosion it isn't a matter of care, it is a matter of manufacturing, during the heat treatment process.

That corrosion pictured appears to be between layers of metal causing a blister and then allowed to develop into a full blown exfoliation condition.

I will give you the point it should have been found much earlier.
 
Tom-D said:
If this is inter granular corrosion it isn't a matter of care, it is a matter of manufacturing, during the heat treatment process.
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Without actually examining the spar, I can't say for sure what sort of corrosion it is, but I've seen surface corrsion due to condensation on top of the spar before in neglected Grummans, and never heard of it in ones that have been properly inspected and cared for. So, if it's a manufacturing defect, it's the first I've heard of one.

That corrosion pictured appears to be between layers of metal causing a blister and then allowed to develop into a full blown exfoliation condition.
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The spar does not have "layers of metal" -- one solid piece which is, IIRC, cast, machined, and shaped.
 
Ron Levy said:
Without actually examining the spar, I can't say for sure what sort of corrosion it is, but I've seen surface corrsion due to condensation on top of the spar before in neglected Grummans, and never heard of it in ones that have been properly inspected and cared for. So, if it's a manufacturing defect, it's the first I've heard of one.
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The corrosion caused by the circumstances that you describe is direct chemical attack, it does not cause lifting of the surface like a blister, it simply eats away the surface.
Ron Levy said:
The spar does not have "layers of metal" -- one solid piece which is, IIRC, cast, machined, and shaped.
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All metals have grain boundaries, even those that are one piece, Intergrandular means it starts between those grain boundaries and the resulting corrosion products swell the metal causing blisters, which will eventually erupt thru the surface, such as what we see in the picture.

Pipes are not cast, they are extruded thru dies, stretched and expanded to size and thickness. or they are rolled as in a seamed tube, the only machining done is to cut to length. squaring the ends an such.
 
Ron Levy said:
So, if it's a manufacturing defect, it's the first I've heard of one.
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WE are starting to see corrosion like we have never seen before as the fleet ages. All the 1&200 series Cessnas have an aluminum block machined to fit the fuselage spar carry thru where the wing attach bolt passes thru it to attach the wing, these blocks are now showing the same problem, earlier we never had a problem with these blocks but now we are.

For tubes to be used as off the shelf manufacturing stock it is not uncommon to see intergaranular corrosion, all one needs to do is examine the discarded irrigation pipes in the salvage yards it is why the framers throw it away. Granted those pipes are much thinner, but fail for the same reasons. "corrosion"
 
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Tom-D said:
WE are starting to see corrosion like we have never seen before as the fleet ages.
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For someone who several posts up says he does not deal with Grummans, it's hard to accept as credible your statements about what you see in the aging Grumman fleet.
 
Ron Levy said:
For someone who several posts up says he does not deal with Grummans, it's hard to accept as credible your statements about what you see in the aging Grumman fleet.
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I don't see aluminum in a Grumman any different than aluminum in any other aircraft.

Going by the picture posted, that looks very much like Intergranular corrosion, no other corrosion will cause a blister and cracking like that.

direct chemical attack etches the surface and leaves pitting, not huge cracks across a bulge/blister like shown.

Were I a Grumman owner with a tube spar and the area is known to have a corrosion problem, like you've mentioned. I'd be all for having the spar removed and a ultra sound inspection pulled on it.
When it passes I'd have it cleaned etched and corrosion proofed by priming and painting, before replacing it.

And I sure as he!! wouldn't buy one with out that inspection being completed.
 
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Their is some real junk Aircraft out their I have seen several that should have gone to the bone yard but are still flying because some IA will still sign the annual off. I am not sure this will ever change as the good old boy annual is still going to happen. All I can hope for is someone isnt using my name and number without me knowing about it to sign them off.:rolleyes:
 
While it's not clear from the picture exactly where on the spar the corrosion is, it is possible to miss that type of corrosion on the Grummans during an annual inspection. If I had to guess, the corrosion is under the landing gear brackets attached to the spar, which cannot be seen without removing the landing gear, a VERY difficult procedure not listed in the annual inspection checklist.

I had a hard landing in my '79 Tiger and had to replace one gear leg. When I removed the attach brackets from the spar, I found corrosion, though not to the extent in the picture. I suspect there is a large percentage of the Grumman fleet flying with this corrosion, especially if tied down outside. If you own a Grumman and have not inspected this area, I would highly recommend it be done immediately. Access to the gear attach bolts is VERY difficult without the right tool. I removed the other gear leg and found corrosion on that side, too. I cleaned, alodined and epoxy primed the area prior to reassembly. (And the mating parts, too)

The '79 Tigers had a lot of corrosion treatment at the factory. Early Grummans did not, so I would suspect worse corrosion if stored outside.
 
Actually, I think corrosion treatment at the factory on the AA5X's began sometime during manufacture of the 1978 models.

There certainly is a lot of speculation in this thread about corrosion the poster hasn't personally witnessed...along with a lot of implied conclusions about Grummans from someone who doesn't work on them nor even know where their fuel tanks are located. I was looking for more data, less conjecture.

Jack
 
Ron Levy said:
Folks familiar with Grummans will recognize the top of the spar, probably in the wing root area based on what I see.

You're reading it wrong. The spar is just a hollow aluminum tube -- no "sheets" involved. This corrosion is on the top of the outside surface.

No, "we" don't. That appears to be on the top of the spar, which is relatively easily inspectable and part of the annual inspection. The only way this happened is if the plane went a very long time without proper inspection or care.

I know you have some personal issues with the way Grummans are constructed, but this is not an indication of any sort of generic problem, just a neglected airplane. I'm sure you'll find similar examples on the structures of neglected Cessnas, Beeches, Pipers, and even Fairchilds.
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:confused: I thought they were steel?
 
brien23 said:
Their is some real junk Aircraft out their I have seen several that should have gone to the bone yard but are still flying because some IA will still sign the annual off. I am not sure this will ever change as the good old boy annual is still going to happen. All I can hope for is someone isnt using my name and number without me knowing about it to sign them off.:rolleyes:
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I've been looking at more and more over the last few years. I think that a lot of the bottom 'never before seen' priced aircraft have been the ones that were ramp queen junkers for sale at 'flying plane' prices that didn't sell in the decade before the economy collapsed. Now they have the prices down to salvage prices to get out of the liability and people want to believe that they can now have a good flying one for that price and are dissappointing when they show up and look at a dg that's ready for scrapping. This never ceases to amaze me since the thing was advertised at scrap price, a third of what a good one goes for. All the 'good deals' were gone in the first 6 months of the market collapse. Since then it's been "you get what you pay for".
 
This thread reminds me of the vintage Fram oil filter commercials on TV.

"You can pay me now or pay me later"

Thankfully ther are replacement parts for both the Grumman in question and the Cessnas Tom D works on.
 
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