Cessna Adding Corrosion/Fatigue Inspection for Aging A/C

[RFlyer]

Interesting story out by Avweb yesterday - Cessna will be updating the service manuals for their 100 and 200 series aircraft which were manufactured between 1946 and 1986. I think the 1986 cutoff date is because a/c manufactured after that had primer on the interior aluminum surfaces. The story from Avweb can be viewed at: http://www.avweb.com/avwebflash/news/Ce ... 830-1.html.

There are links to Cessna's power point presentation and a Youtube video. The video summarizes what's covered in the PPT. Seems like they are mostly talking about high-time aircraft in the 8000+ hour range on the airframe. But they also make the point that corrosion is more related to calendar time than aircraft flight cycles and machines in coastal areas fare the worst - no surprise there!

Prime areas discussed are:
- elevator trim tab
- vertical stab attach points
- Horizontal elevator spar attach points
- Door post / spar attach points
- main spar carrythrough, especially on C177/C210
- Engine mounts
- Landing gear

Inspection is non-destructive according to the Cessna documentation, although I guess if serious problems are found, they could be destructive to the bank account!

[iflyforpie]

Well, we are going through some of those additional inspections right now on our 337. For the most part, I've found that they are simply duplicating inspections that you should be doing in the first place, but highlighting problem areas and doing a little CYA for what they specifically want you to inspect. I think they also want to increase the maintenance requirements on these aircraft to hasten their retirement.

We thought it was a lot of BS at first. The only other time I've seen CPCP programs was on turbine aircraft with things like lavs and thousands more hours and cycles in corrosive environments. Our planes get spoiled being in a dry-belt and hangared all the time. The only time I fly in rain is when I want to give the bird a good wash.

I expected to find corrosion on the elevator and horizontal stab, as it is in the exhaust efflux from the rear engine. Minor surface stuff only.

What I didn't expect to find was the massive amounts of corrosion on the leading edge wing root rib on this two-bit inspection item that should have taken me 30 minutes to complete....



I got lucky and found a rib used where the holes line up and Cessna never got back to me on a new one (I at least wanted to have a chuckle on the price, I was betting at least a grand and maybe two) Good luck making one from scratch, 0.050 2024 T6 with compound bends and joggles---you'd need a bloody drop forge!. Everything goes through it (fresh air vents, R/H fuel selector tele flex, aileron balance cable, all of the wiring, and a fuel cross feed line), plus it picks up the fwd wing fitting and the fasteners go through the main spar and required the removal of the R/H aux fuel tank. I've found out that the 3/6" x 7/8" Hi Locs that go through the spar are a rare commodity with a 30 day lead time and had to buy two bags of rivets for want of four dash 6 (3/16") rivets I did not have in my stock.

Just a little taste of how even a basic re and re of a structural member can turn into a clusterfuck. Gear fittings on 172s are way easier. I hope to have it wrapped up by Christmas...

If you get a plane with a bit of surface corrosion inside (white powdery residue), just leave it alone. It looked like that ten years ago and it will look the same ten years from now on a light aircraft. That is the ALCLAD doing its job. As soon as you attack it with scotch brite (the brown aluminum-oxide pad, don't ever let me catch you using a green pad on a plane!) you will be fighting even worse corrosion the next time. Then the scrub, etch-alondine, prime, and CPC cycle that ends when the part disintegrates or you run out of money or sanity.


Also, for those extra inspections, make sure you pay attention to the hours and calendar requirements. On ours for the removal of both the wings and the tail booms, it said 12,000 hour or 20 years (they are all over 20 years), but, it said that for aircraft under 12,000 hours, you could do a basic visual and if there were no defects, skip the detailed inspection. Saved a ton of work not having to pull those off....

[Troubleshot]

on the topic of corrosion, do you guys find ACF-50 actually neutralizes corrosion, or even slows it down? They claim it "actively penetrates through the corrosion deposits to the base of the cell where it emulsifies and encapsulates the electrolyte" but I have never heard if this stuff actually works. I have seen it everywhere over the years but I am curious to know if any of you guys religiously use the stuff and have seen results.

[Colonel Sanders]

If you get a plane with a bit of surface corrosion inside (white powdery residue), just leave it alone

When I see what looks like baking soda on the metal (surface corrosion) I hose it down with corrosion-X or ACF-50, both of which do pretty much the same thing. Makes a terrible mess - it runs out at the low points. Not a good thing to do before a paint job! I might be wrong, but airframes that have been misted with corrosion-X/ACF-50 years ago, might have less corrosion than untreated airframes, especially if they are exposed to any significant humidity/salinity. It's not something I do every year. A hangared aircraft in a dry, salt-free environment, I would mist it every few years. Parked outside, I would do it every year.

AME's around here have been hosing down the carry-throughs on 177/210 around here with Corrosion-X for years.

[HS-748 2A]

(the brown aluminum-oxide pad, don't ever let me catch you using a green pad on a plane!)

You sound so militant Pie' and where did you ever get that idea anyhow~!?

'48

[Big Pistons Forever]

.

Nasty It kind of makes you wonder what the inside of the wings look like in all the other Huff and Puffs out there, as I doubt very many get the level of care you are giving during inspections........

[iflyforpie]

.

Nasty It kind of makes you wonder what the inside of the wings look like in all the other Huff and Puffs out there, as I doubt very many get the level of care you are giving during inspections........

Well, I confess I missed this one because it obviously didn't just pop up this summer. I believe it has a lot to do with that black CAT hose (not SCAT, which is the orange stuff) from the fresh air vent rubbing up against the rib. The other side had SCAT tubing and no problems at all. It seems like whenever I see this black stuff there is corrosion underneath of it (like when it attaches to a flange on baffling for generator/mag cooling).

The rest of the plane looks pretty much like it did back in 1966...

[iflyforpie]

You sound so militant Pie' and where did you ever get that idea anyhow~!?

'48

I know I sound militant, but it's been going around the boards and is very contagious...

viewtopic.php?f=27&t=77425&p=726517#p726517

[HS-748 2A]

That one was a rare occurance and I just can't help but bask in the glory..

I always enjoy your posts IFFP.

'48

[tyndall]

I believe it has a lot to do with that black CAT hose (not SCAT, which is the orange stuff) from the fresh air vent rubbing up against the rib. The other side had SCAT tubing and no problems at all. It seems like whenever I see this black stuff there is corrosion underneath of it (like when it attaches to a flange on baffling for generator/mag cooling).

I've seen many a Musketeer with severe fuselage corrosion due to Beech using that crap for fresh air ventilation. When you start to see the white powder on the outside of the plane you know its never had a good going over.

[SpiltMilk]

no

[TimothyTM]

This safety standards is a good example that major manufacturers must follow. It brings something positive to table and will elevate safety standards. I have read some similar articles related on the issue.

http://airsoc.com/articles/view/id/4fbf ... =10&evp=tl

and

http://integritythatworks.wordpress.com ... n-program/

[sidestick stirrer]

That cheap, black tubing is what has caused a lot of corrosion in the spar carry-through structures in C-177's. it has a very-short lifespan compared to SCAT and the inner wire rusts quickly.
I religiously misted my 177 with ACF-50 until reading about its unintended ability to actually allow rivets to work free, in that the thin-film would work between the pieces of metal that the rivet was supposed to hold tightly together, somewhat reducing the friction that was assumed to be created between the two pieces.
Although not yet an issue in my 1968- vintage machine due to having only 1850 hours TT, the last advice I received was to keep any TFD( thin-film dielectric) away from the biggest rivets; those near on on the main spars, the landing gear mounts, etc.