Cracked aluminum cowling

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Mtns2Skies

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Mtns2Skies
Any thoughts on what to do? I'd rather not replacing the cowling if I can help it, but I spoke to two aircraft aluminum welders in the area that weren't confident they'd be able to do the work successfully.
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That stuff isn't welded. It gets a riveted patch. That cowl (if it's a Cessna) is made of 2024, most likely formed in the -O condition and then heat-treated after forming, and that alloy is not weldable anyway.
 
What is that big bulge of stuff to the left of the crack? Tell me that isn't a JB Weld repair covering another crack.
 
Most exterior & structural skins are 2024 aluminum, which cannot be welded. An A&P would need to strip back the paint and what ever else was used prior to patch/hide the crack. Would not be surprising to find corrosion as source, contributor, or post crack failure.

This possibly could be patched with doubler on the inside under standards & practices Technique congruent with aircraft’s service/maintenance manual. I’d flush rivet and repaint to minimize visibility. Just a guess...The manufacturer may even require flush rivets since this is in the path of prop wash. Check with them for advice.

Consider also having a knowledgeable IA have a look as well.
 
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Timbeck2 said:
What is that big bulge of stuff to the left of the crack? Tell me that isn't a JB Weld repair covering another crack.
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I noticed that too. It looks like a welding attempt has already been made (and failed) to me...

A decent sheet metal guy should be able to make a patch for this.
 
The rivets on the top cowl aren't there on mine. There are some rivets a couple of inches aft of that cowl fastener at the seam where the cowl transitions to the curve. Have you looked at top and bottom cowl on the inside? I wonder what repairs have been done previously. In any event I wouldn't fret. A good sheet metal guy can fix it as good as new and it'll look fine, except you'll ned to paint the patched area and that'll make it stand out. It's like tipping that first domino over!
 
mondtster said:
I noticed that too. It looks like a welding attempt has already been made (and failed) to me...
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That's correct, Which is why I assumed it was weldable, but that appears to be false. I'm not sure when the weld was done, but it held for at least the 3 years I owned the plane and judging by the paint in the area a good decade or so more.
 
I think I can see why it cracked. Look at the gap between the upper and lower cowling before and after the cracked area. It appears there isn't a gap, possibly even overlapping of the two at the point of the crack. After it is repaired perhaps consider filing that part down for a uniform gap all the way across.
 
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NordicDave said:
Seriously. We have a flight school 172 parked outside 24x7 on our field with 27,500 hrs TT. It looks nicer than this.
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Clip4 said:
That is a rough looking airplane.
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@Clip4 and @NordicDave How are your comments relevant at all to this discussion?

If you can’t get the crack fixed in the near term, maybe your mechanic could do a quick (and large perhaps) stop-drill hole to prevent it migrating any more. I know my cowling has a few small hairline cracks (around the oil fill door for example) that are stop-drilled and they seem to have stabilized for a few years.
 
Matthew Rogers said:
@Clip4 and @NordicDave How are your comments relevant at all to this discussion?

If you can’t get the crack fixed in the near term, maybe your mechanic could do a quick (and large perhaps) stop-drill hole to prevent it migrating any more. I know my cowling has a few small hairline cracks (around the oil fill door for example) that are stop-drilled and they seem to have stabilized for a few years.
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Relevant because many times an issue is caused by lack of proper maintenance.
 
Clip4 said:
That is a rough looking airplane.
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It's pretty obvious the weld repair was painted over with hardware store enamel years ago. That's why it has such, uh, patina.
 
I don’t think it’s been welded. Looks like body filter. Have it taken down to the clean metal to see what’s really going on. Then patch it properly. That’s all it needs. Check the shock mounts. I bet they are trashed.
 
No shock mounts on my 180.

It looks like that area’s got some filler. The scrape in the paint goes pretty deep and has that JB Weld patina.

I was wrong about the rivets, too. Mine are close to the same. 1CDAB9EA-5696-425E-BBC6-9FD8D2F32C27.jpeg
 
Thanks for the tip Stewart! I'll get that ordered with my interior, should be easier than messing around with an obviously messed up nose bowl. I'm going to go in for paint this year anyway, so now's good timing to get it fixed the right way.
 
Happy to help. Give us a pirep when you’re finished.

Are you installing the interior yourself? I can give you a few hints. Mostly to give up coffee on the day you do the rear side panels. The windows channels will test you patience.
 
Looks like someone tried to fix the crack with JB-Weld and missed. First thing to do is stop-drill the darn thing so it doesn't get any longer then a simple doubler patch to restore the integrity. She ain't no beauty queen so no need to get carried away. Rampers run into airliners all the time, they're literally covered with scab patches and nobody seems to even notice.
 
Mtns2Skies said:
You've seen a 4"x4" part of my airplane. I invite you to have intimate relations with yourself:)
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Cracks add character (non-structural ones!) :)

It might be a fun project to make the doubler yourself. Get a little block of wood, dial in the proper radius with a disc sander, then use it as a form to pound out that little sucker. Maybe an A&P needs to install the piece and record the repair, but for a moment you can pretend you're at Carrozzeria Scaglietti, making a panel for a Ferrari sports racer. :)
 
Don't know why that can't be patched with a doubler. Pretty simple repair. I have a couple of patches over cracks on the edge of the upper cowling on my AA-5 that have been acquired over 35 years. Those patches ain't never gonna crack again in that spot. Indeed, it's a lot cheaper than replacing the whole cowling piece. It doesn't even look that ugly. It just adds character...
 
The first thing to do is to find out the alloy of aluminum used. Write the manufacturer. Many aluminum alloys are quite weldable and this an alloy that can be easily formed as it has compound curves so it might be. The you either go to a good welder with a TIG machine or rivet on a patch. Gas welding aluminum is very difficult as you can't tell the temperature of the material by color and you could just melt it through. A patch can still look quite nice if you have or make parts that fit together and put the patch part on the inside.
 
Hard to tell from the photo, but it kind of looks like some inter-granular corrosion going on in that area.
 
s-l500.jpg
 
Snowmass said:
The first thing to do is to find out the alloy of aluminum used. Write the manufacturer. Many aluminum alloys are quite weldable and this an alloy that can be easily formed as it has compound curves so it might be. The you either go to a good welder with a TIG machine or rivet on a patch. Gas welding aluminum is very difficult as you can't tell the temperature of the material by color and you could just melt it through. A patch can still look quite nice if you have or make parts that fit together and put the patch part on the inside.
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The Cessna service manual for that airplane will have a Structural Repair Chapter that will specify the alloy. Most were 2024, which is a non-weldable alloy. Too much copper in it, and welding destroys the heat-treatment.
 
chemgeek said:
Don't know why that can't be patched with a doubler. Pretty simple repair. I have a couple of patches over cracks on the edge of the upper cowling on my AA-5 that have been acquired over 35 years. Those patches ain't never gonna crack again in that spot. Indeed, it's a lot cheaper than replacing the whole cowling piece. It doesn't even look that ugly. It just adds character...
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That area is very difficult to patch, which is why someone tried to goop it somehow. There's a flange and sometimes a tab attached to the top cowl, and they fit into the top inside of the lower cowl. The camlock sockets are attached to the flange. It all leaves very little room inside for a patch, so one would most likely have to form a patch to fit on the outside, extending it back past that camlock, and using a longer camlock to accommodate it.

The Selkirk nosebowl is the way to go. The aluminum around that nose is seriously stressed when formed, and after heat-treatment it's pretty hard, which can also mean brittle, and thousands of hours of being pounded by prop blast and vibrated by baffle seals chafing at it just cracks it. The secret to making them last longer is to look closely at them at inspection time, and dealing with any small cracks that appear by dressing them out, stopdrilling when necessary.
 
An external patch could be made very strong when riveted on. Use about any soft alloy so you can form it to the compound curve. Use thickness to offset softness for strength. Extend rearward and simply cut a hole to clear the camlock OD. BTW when you find out the price of a new cowling you will think they misplaced the decimal point.
 
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