Corrosion areas on a Skyhawk?
- Thread starter cbmontgo
- Start date
tonycondon
Gastons CRO (Chief Dinner Reservation Officer)
low points 
and wherever the mice nest.
and wherever the mice nest.
Skylane81E
Final Approach
If Cessna glued black rubber pads onto the inside of the skins corrosion is probably hiding under them. Early 80s also had issues with filiform corrosion under the paint.
cbmontgo
Pre-takeoff checklist
Can most of this be seen with a normal "panel removal" inspection?
Are there any wing spar/structural corrosion problems that are commonly known on these?
Skylane81E
Final Approach
The filiform is on the outside so easy to see, the rubber pads you might not seethe corrosion, but EVERY pad I've ever removed had a healthy dose of corrosion under it. Not a hard fix if the corrosion hasn't gone too far
Dan Thomas
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Dan Thomas
In the cabin ceiling, where moisture from the occupants' breathing condenses in cold weather. Under the carpets, where water from melted snow or otherwise wet shoes gets and stays there. Anywhere in the belly of a neglected airplane, where dust and stuff plug the belly drain holes. In the elevator, which has dandy holes in the inboard ribs for birds to get into and nest. Their droppings corrode stuff. Push the rudder to one side and get your eyeballs right up against the rib and look inside with a light. Get a look at the elevator torque tube while you're at it; it's a steel tube riveted to aluminum stuff, a recipe for galvanic corrosion. Birds also get into the wings through the holes in the aileron bay spar. Look at the battery box; some are rotted out (acid from overfilled batteries) and their attaching bracketry can be found loose. Engine mount tubing corrodes, too, and it doesn't take much to write off the mount, which was covered with cheap paint that the heat burns off.
Some wheels will be found corroded. Many were made of magnesium, which corrodes really quick. Got to take the tires off to get a good look. And neglected wheel bearings are almost always corroded.
There has been recent concern about the main gear spring legs. They can corrode anywhere along their length, but I'd expect the most sensitive area to be at the bend at the top of the leg, under the plastic fairing. Lots of stress concentrated there, and any pitting at all is bad.
The 172 has crack-prone areas, too. Check the forward horizontal stabilizer spar by taking off the fin root fairings and looking forward into the stab. There's a lightening hole on the center of the spar that cracks outward when people push down on the stab to lift the nosewheel and turn the airplane on the ground. Bad technique. The aft doorposts crack right at the point where they join the underfloor bulkhead, got to take the plastic covers off those posts and look forward underneath the aileron cable pulley and check the small cutout radius for cracking. Really hard to spot. The forward doorposts can crack at the lower door hinge attachment. Firewalls crack at the cowl shockmount brackets. The 172 muffler is crack-prone; look at the end plates. And check all the exhaust risers right at the clinder flange for cracks in or near the weld.
Dan
Some wheels will be found corroded. Many were made of magnesium, which corrodes really quick. Got to take the tires off to get a good look. And neglected wheel bearings are almost always corroded.
There has been recent concern about the main gear spring legs. They can corrode anywhere along their length, but I'd expect the most sensitive area to be at the bend at the top of the leg, under the plastic fairing. Lots of stress concentrated there, and any pitting at all is bad.
The 172 has crack-prone areas, too. Check the forward horizontal stabilizer spar by taking off the fin root fairings and looking forward into the stab. There's a lightening hole on the center of the spar that cracks outward when people push down on the stab to lift the nosewheel and turn the airplane on the ground. Bad technique. The aft doorposts crack right at the point where they join the underfloor bulkhead, got to take the plastic covers off those posts and look forward underneath the aileron cable pulley and check the small cutout radius for cracking. Really hard to spot. The forward doorposts can crack at the lower door hinge attachment. Firewalls crack at the cowl shockmount brackets. The 172 muffler is crack-prone; look at the end plates. And check all the exhaust risers right at the clinder flange for cracks in or near the weld.
Dan
Last edited:
denverpilot
Tied Down
Yeah, those "sound deadening" things. Every mechanic I've ever talked to rips them out of every Cessna they find them in. There is often corrosion behind them, for sure.
They're actually plastic/rubber coating over a lead interior... an attempt by Cessna to dampen noise/vibration in the aluminum skins.
Bummer for all of us is... Cessna used a hygroscopic glue. So water enters the glue behind these things and gets trapped there against the aluminum. For years.
Cessna Pilot's Assn. also says toss 'em anytime you find 'em still attached.
Skylane81E
Final Approach
Dan tha man there
Let'sgoflying!
Touchdown! Greaser!
All wing spar carry-throughs should be on everyone's radar and deserve a good look.