That darn avionics cover

[billsheila]

Question for some 337 long timers...anyone ever have trouble with water entering the avionics cover? I have had the seal replaced, but I think it is coming in via the 1/4 turn screws. I am in hangar mostly, but on a 2 week vaca and its raining! I note Cessna engineers must have been worried about the same thing...they built this little plastic tray with two drains in it that go down to the belly, but it doesn't really work, I think the water finds a path before it ultimately drips and tends to miss the tray. Any experience or ideas, before I damage something. BTW: I have a Bruce's Custom Cover on order, which will work on the ground pretty well I hope...but if I am right and it is the screws (I am almost 100% certain it is) then this would be an issue in flight as well.

Thanks
Bill

[edasmus]

Hi Bill,

Yes, I had a very expensive experience with this years ago at Oshkosh. It rained heavily one evening and bunches-o-water entered those covers and caused all sorts of trouble.

Anyway, replacing the seals is good but if it is the screw holes you are worried about, make sure you have the proper hardware installed. The "screw bases" (not sure exactly what they are called but it would be what the screw screws into attached to the airframe) are cupped. That is to say they are not open ended. There is a service bulletin on this but I cannot recall the number at the moment. They will not allow water to pass through.

All this said, I have very little faith with the entire arrangement so as an added precaution, I completely run a bead of silicon around the entire joint on both covers. It is rather unsightly and I suppose most would not want to deal with the cosmetic, flaw but for me, after spending $5000 plus to repair the water damage, an unsightly bead of silicon seemed like a much better option. Both my maintenance shop and avionics shop do not even bother asking me anymore. They know that if those covers have reason to be removed, they seal them all back up as neatly as they can knowing that I don't mind the appearance. Just keep the water out!!!

Ed

[billsheila]

Ed;
Well I have at least for now headed down exactly this path (ie sealant). I spoke to my mechanic over the phone and while he had previously warned against this, he admitted it was better than nothing, so I put a glob of silicone on each screw before locking it down, and I am hoping that is enough to hold things for now until either a better solution is found or this may end up being the long term solution. As you say, the clean up each time the panel comes off will be the next challenge.

Regarding the cupped screws, interesting idea, but unless the cups are rather large and there is somewhere for the water to go, I agree with you being suspect of this solution.

Wet and worried for now...but thanks again for the help!

Bill

[Gord Tessier]

We use a form of clear duct tape and seal the whole thing from the outside. It's not as cosmetically appealing from the outside but it does the trick.

[DBrugg]

Hi Bill,
Had the same problem and for this reason I purchased a cover from Bruce.

http://www.aircraftcovers.com/

He has an extended option that covers the avionics covers.
Doesn't help your inflight concerns. I did have clear 3M tape, similar to paint chip guard over the seam and fasteners until my cover showed up. Since I'm pressurized I don't have the inflight concern.

Dan
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[Gord Tessier]

I have Bruce's covers as well. They are excellent. Unfortunately, they can't help you inflight when you go through rain.

[Ernie Martin]

I'm on my second 337, I live in Miami, I don't hangar the plane, and I have a two-prong solution that works.

First, I don't use silicone because of what's left behind when you have to remove the cover. Instead I use Vaseline. I put globs of it along the gap and on each screw, and I work it in. Second, I made myself a cover using the neoprene/PVC flexible shower floor liner used below the small mosaic floor tiles (see picture) and keep it secured using 3 bungee cords.

The liner is sold at Home Depot and Lowe's. It's on a roll about 4 feet wide and you cut what you need (about 1.5 feet) to make sure it covers all the way up to the windshield molding.

Here are the positives: it works, it's easy to remove, it's inexpensive. On the negative side, the liner doesn't protect in flight, although that has never been a problem for me, either because the Vaseline is sufficient, the time I spend flying in the rain is generally short, or the airflow keeps much of the rain out.

Ernie

[Skymaster337B]

I suppose Vaseline will work, but I would be afraid of it melting and running. I use clear silione to seal the whole thing...easy to remove and replace too.

[billsheila]

That is what I ended up using for now, but have not yet tried to remove it. You say it is easy. I hope you are right!

[edasmus]

It will come off ok. You may have to work a little, but anything is better then filling up the back of the panel with water. Don't ask me how I know! ;o)

Ed

[sloutitt]

We use a roll of shrink wrap and go once around the plane. In flight we have never noticed any water I think due to the air flow.
Sandy Loutitt,
N81C