Corrosion question

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FE_PLT
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Corrosion question

Post by FE_PLT »

What would you guys think this means: "Level 1 corrosion on non critical parts". It's from an annual inspection on a Piper Cherokee 140. Just curious... Thanks.
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flyinggreasemonkey
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Re: Corrosion question

Post by flyinggreasemonkey »

Probably an ACF50 or CorrosionX application.
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c170b53
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Re: Corrosion question

Post by c170b53 »

Its a definition of the extent of the corrosion, Levels one to three. There's two parts to that statement one, the level of corrosion that was found, part two the non critical part statement. I'm guessing the part that does not take a load in the structure ie trim, fairings, access panels and the like. Level one is generally a single spot within a defined area.
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FE_PLT
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Re: Corrosion question

Post by FE_PLT »

So can we assume it's only surface corrosion?
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c170b53
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Re: Corrosion question

Post by c170b53 »

Its a bit subjective based on the person doing the inspection but local level 1 corrosion would be repaired by removing the corrosion by acceptable methods and within the SRM guidelines (if one exists). Level 2 would be repaired by part replacement. In the case of light skin corrosion (pitting) as someone mentioned application of ACF 50 will likely slow that process down. Most aircraft will have some form of corrosion in the structure and depending on many variables, sometimes it's a problem and sometimes it doesn't pose a threat to airworthiness of the aircraft. The biggest threat is corrosion that's has not been detected and is not visible in a component such as a spar cap. Take the Cessna 100 series, where the spar cap at the inboard end is an extrusion. The wing tank access panel nut plates are steel, with some relative movement between the screw, screw nut plate and the aluminum spar, a bit of fretting and injection of iron oxide into the grain of the extrusion, add moisture and eventually the initial dissimilar metal corrosion will be found at the exfoliation stage. Hopefully that is found before the part snaps but if the corrosion runs in the grain and bursts out on the forward side of the spar it's likely to go unnoticed. Sound far fetched ?
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niss
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Re: Corrosion question

Post by niss »

For inspecting the spar, is it possible to forgo the labour to completely disassemble and just drill a hole so you can inspect with the bore scope and patch afterward?
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SeptRepair
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Re: Corrosion question

Post by SeptRepair »

c170b53 wrote:Its a bit subjective based on the person doing the inspection but local level 1 corrosion would be repaired by removing the corrosion by acceptable methods and within the SRM guidelines (if one exists). Level 2 would be repaired by part replacement. In the case of light skin corrosion (pitting) as someone mentioned application of ACF 50 will likely slow that process down. Most aircraft will have some form of corrosion in the structure and depending on many variables, sometimes it's a problem and sometimes it doesn't pose a threat to airworthiness of the aircraft. The biggest threat is corrosion that's has not been detected and is not visible in a component such as a spar cap. Take the Cessna 100 series, where the spar cap at the inboard end is an extrusion. The wing tank access panel nut plates are steel, with some relative movement between the screw, screw nut plate and the aluminum spar, a bit of fretting and injection of iron oxide into the grain of the extrusion, add moisture and eventually the initial dissimilar metal corrosion will be found at the exfoliation stage. Hopefully that is found before the part snaps but if the corrosion runs in the grain and bursts out on the forward side of the spar it's likely to go unnoticed. Sound far fetched ?
Nice summary. This is a topic I feel that is not covered nearly enough as we continue to work on aging aircraft.
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FE_PLT
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Re: Corrosion question

Post by FE_PLT »

Thanks a lot c170b53. Really appreciate your replies. I am still debating whether I should buy that aircraft. I'm gonna need an AME in the Okanagan Valley for a pre-purchase inspection in the next couple days. Any volunteers? :mrgreen:
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SeptRepair
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Re: Corrosion question

Post by SeptRepair »

I cant think of any qualified Ame's in the valley that know geneal aviation aircraft. Ifly...you know anyone? :lol:
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iflyforpie
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Re: Corrosion question

Post by iflyforpie »

SeptRepair wrote:I cant think of any qualified Ame's in the valley that know geneal aviation aircraft. Ifly...you know anyone? :lol:
Not anybody I would recommend that is still kicking around...
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crazy_aviator
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Re: Corrosion question

Post by crazy_aviator »

Come on over to skytek aircraft in Vernon BC. I could do the PPI for you . We are a very thorough shop and i have 26 years in pipers and cessnas. I dont own the company, just work there. A GOOD PPI can save you both $$$ and a BIG heartache!!! or is that headache ,,,, :shock:

PS: Good idea to pull the tanks, check your cam/lifters if age, idleness is a concern, hard landing crease evidence etc.
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