Replacing engine baffle

murphey

murphey

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murphey
I need to replace about a foot of baffle on the engine on the cherokee. Is this an owner item or does it require A&P signoff?
 
When I had to replace the baffling, I removed the old, and let the AP install new. Mechanics love when you do the grunt work.
 
Appendix A to part 43, (c) Preventive maintenance is what you can do on your own.

For replacing baffles, You would want your A&P to sign off on your work if you want to make sure you are coloring inside the lines unless you want to argue that C 12 applies - which is best answered by your particular IA
 
Ask your A&P if you can do the work "under supervision", then call him to inspect and sign off. Working "under supervision" is the best of both worlds. Get prior approval by your A&P/
 
murphey said:
I need to replace about a foot of baffle on the engine on the cherokee. Is this an owner item or does it require A&P signoff?
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Are you talking about the metal baffle or the baffle seals? If the seals are they riveted or stapled on?
 
And be sure to re-supervise your A&P for material selection, workmanship, fit, etc. I'm amazed at how informal this critical element is designed in many OEM installations, for such an important function of providing adequate engine cooling.
 
Bell206 said:
Are you talking about the metal baffle or the baffle seals? If the seals are they riveted or stapled on?
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The seals are riveted on. Next time at the airport, will take photos to remind me what to buy. I don't need the whole package - for 50 yrs old, most of the baffles are in excellent shape. Just the one furthest from the prop.
 
murphey said:
The seals are riveted on.
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FWIW: while I agree in general the prevent-mx list is not set in stone, I don't think one can simply just add whatever to that list. However, as I was taught on several levels, if one can "associate" a non-listed task to one of those existing 31 items it was possible for a pilot to perform the work. In my opinion, repairing a foot long piece of baffle seal could fit into item 12 of the prevent-mx list and be signed off with an appropriate reference by a pilot. But a quick call to your APIA may be appropriate as well.
 
If the 50 year old baffles are not silicone--replace them.
And line the underside of the cowling, where the baffling bears, with metal foil duct tape.
 
MooneyDriver78 said:
Or you can use this (frictionless tape):

https://www.mcfarlaneaviation.com/products/product/CS085X3X36GBF/
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I used this stuff on either the 310 or 414, I forget which. Maybe it was both. Anyway, I was very impressed with it and considered it to be worthwhile.

I did baffles on the Aztec, 310, and 414. I believe it was done under supervision in all cases but it's been long enough ago that I forget how we did the logbook entries. You should talk to your A&P on this before doing it in my opinion, but the work is pretty easy to do, just requires some time, patience, and attention to detail.

Baffles are an area where most A&P/IAs frankly do a poor job. Tips:

- Make sure you don't have any wrinkles where the baffles touch the cowlings. This should be flat as that seals air in
- Go around the flexible baffles where they rivet to the metal bits and add a bead of silicone everyplace air might go through. You'd be surprised how many of those areas there are and it makes a big difference

On the 310 I got the CHTs down around 30-40F with that work and saw a noticeable performance improvement. On the 414 I didn't have an engine monitor (just factory gauges) and so I forget how much of an improvement I had, but it was still noticeable.
 
Ted said:
Tips:

- Make sure you don't have any wrinkles where the baffles touch the cowlings. This should be flat as that seals air in
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We did a major overhaul a few months ago. As a part of the overhaul, we insalled new metal baffles with new flexible seals. The flexible seals have about three wrinkles "bulbing" up about 3/4" or so high and about the same horizontally. I have tried, but have not been able to get them to lay flat against the underside of the cowling (by the way our IA did a poor job, like you said). Do you have a suggestion for getting the wrinkles out so the flexible seal will flatten out?
 
somorris said:
We did a major overhaul a few months ago. As a part of the overhaul, we insalled new metal baffles with new flexible seals. The flexible seals have about three wrinkles "bulbing" up about 3/4" or so high and about the same horizontally. I have tried, but have not been able to get them to lay flat against the underside of the cowling (by the way our IA did a poor job, like you said). Do you have a suggestion for getting the wrinkles out so the flexible seal will flatten out?
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What airplane? Do you have some pictures? I’ve found sometimes I’ve needed to cut the flexible baffles so there are two pieces on a straight section to prevent the wrinkles.
 
I don't have pictures, unfortunately. The airplane is a Cessna 150H. I purchased the new baffles from Airforms. When I called them, they suggested cutting "V's" in the baffles. I tried that, but could not see that it made any difference. I hesitate to get too radical on trimming for fear of ruining the new baffles. The new baffles came with the flexible seals riveted on. Did you just cut a slit in the seal material?
 
You can cut a slit in the material, although depending on how the wrinkles are exactly sometimes I've just used two pieces of flexible baffle material entirely riveted to the new hard parts.
 
somorris said:
I don't have pictures, unfortunately. The airplane is a Cessna 150H. I purchased the new baffles from Airforms. When I called them, they suggested cutting "V's" in the baffles. I tried that, but could not see that it made any difference. I hesitate to get too radical on trimming for fear of ruining the new baffles. The new baffles came with the flexible seals riveted on. Did you just cut a slit in the seal material?
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Cutting a slit will leave one side overlapping the other. Make sure cowl pressure works in your favor when deciding which lays over which. Maybe add a dab of RTV to hold it in place until it takes a set shape. The key is to have the seals positioned properly when the cowl is installed. Make it easy on yourself. If you cut a dart (a vee slice) there are more ways for it to leak. All silicone seals should curl toward the center/front of the engine to maintain pressure.
 
Domenick said:
Ask your A&P if you can do the work "under supervision", then call him to inspect and sign off. Working "under supervision" is the best of both worlds. Get prior approval by your A&P/
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thats what I did, it turned out beutiful and I’ve had many compliments. I’ve been told multiple times that it would have never came out that nice had I hired it done or paid a ton- as you can put love into it most hired hands won’t. I’m not slamming others work- I’m saying something like this can be done better by owner / pilot- “under supervision” of course...
 
I would concur on slits, and then some rtv...

To do mine to perfection took me about 12 hours on a simple Cessna 140... it’s simple work but highly meticulous if you want perfection- and frankly to work properly requires perfection. material-wise what improvement could you do that is good for your engine life that’s less expensive than this? So if you can provide the labor do it.
 
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Thanks, everybody. I will use straight slits and RTV and see how I can make it work out. I have been trying to get an answer to this for a while now, and really appreciate the help.
 
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