Rocket Corrosion/Questions

[Jeff H.]

Under the plane this weekend and noticed two (newish?) corrosion spots on inspections panels.  Under belly, right side, roughly in line with gear.  Any thoughts on why these would corrode (pics attached)?

Very newby owner questions - please forgive me:

1) Is there any concern/risk/difficulty in simply opening these inspection panels up and taking a peek?

2) Noticed that after my last annual there are missing belly pan screws and non-matching screws substituted for originals.  Suggestions for sourcing replacements?

As always, thanks.

[Andy95W]

Looks like something in there is trying to get out.  Remove the inspection panel yourself (totally legal as owner preventative maintenance) and post a picture- and show your mechanic.

[Piloto]

Is the worst zit I have seen on a Mooney. It looks like someone tried to plug the drain hole on the cover for whatever reason. The cover was painted after but the sealing compound caused corrosion and blistered the paint. It is a localized event not to be concerned. Just replace the cover.

José

[Guest]

The four rivets around the corrosion spot suggest some form of patch on the inside of the cover. Get a good #2 Phillips screw driver and remove the panel for further inspection.  You may end up stripping the paint off to treat the corrosion.  Alumiprep, Alodine, primer and paint will be required.

New screws from Aircraft Spruce etc. AN507-832R7 or AN507C832R7 for stainless steel.

Clarence

[jclemens]

I would venture to guess there used to be an antenna of some sort there in the past.

[Yooper Rocketman]

There may be some dissimilar metal corrosion going on.  My Rocket is always trying to develop corrosion on the bottom, any place there is a edge of paint that gets exposed to the exhaust flow.  The lead in the exhaust (as well as probably other corrosive elements) will attack anything it can get at.  I am pretty religious in cleaning the bottom to prevent that from happening.  I've stripped and repainted several panels since I bought it in 2001.  Seems the more frequently I clean, the less I see corrosion trying to start.

Tom

[Guest]

46 minutes ago, Yooper Rocketman said:

There may be some dissimilar metal corrosion going on.  My Rocket is always trying to develop corrosion on the bottom, any place there is a edge of paint that gets exposed to the exhaust flow.  The lead in the exhaust (as well as probably other corrosive elements) will attack anything it can get at.  I am pretty religious in cleaning the bottom to prevent that from happening.  I've stripped and repainted several panels since I bought it in 2001.  Seems the more frequently I clean, the less I see corrosion trying to start.

Tom

That borders on "Plane Porn"

Clarence

[Yetti]

Motorola used to make a rubber plug for plugging antenna holes.  That kind of looks like one.  See if you can find a new inspection panel to replace the current one. 

[aviatoreb]

2 hours ago, Yooper Rocketman said:

There may be some dissimilar metal corrosion going on.  My Rocket is always trying to develop corrosion on the bottom, any place there is a edge of paint that gets exposed to the exhaust flow.  The lead in the exhaust (as well as probably other corrosive elements) will attack anything it can get at.  I am pretty religious in cleaning the bottom to prevent that from happening.  I've stripped and repainted several panels since I bought it in 2001.  Seems the more frequently I clean, the less I see corrosion trying to start.

Tom

Nice...bum.

[Yooper Rocketman]

Ya, well it doesn't look that good now.  That was before the turbo failure.  I cleaned the bottom after that but didn't wax it that time.  I just noticed the last few flights more oil than normal on the bottom (and a slight uptick in consumption).  I start the annual today, so shall see if something on the turbo is leaking or if I developed something else. 

[Steve Dietrich]

 

Looking at it again I am wondering if they riveted a steel washer into the antenna hole and into a backing plate

 

 

Could it be a mismatch of the patch and the cover or the rivits holding it

Edited May 13, 2016 by Steve Dietrich

[Jeff H.]

Thank you very much for all the input.  I was going to apologize for the unclean underside in the original post and forgot.  All y'all were very kind in the comments.

 

[Mark89114]

Well take the thing off and show us what it is or behind it, the suspense is killing me.

[Jeff H.]

14 minutes ago, Mark89114 said:

Well take the thing off and show us what it is or behind it, the suspense is killing me.

LOL.  The weekend is here . . . patience will be rewarded.

[Jeff H.]

On 5/13/2016 at 4:44 PM, Jeff H. said:

LOL.  The weekend is here . . . patience will be rewarded.

Finally got the pictures.  My concern was that the corrosion was coming from the inside.  Not the case. All good and clean on the inside.  Thank you to everyone for your help.

[carusoam]

Nice follow-up, Jeff!

There is a lesson in the photos we all get. Corrosion can be pretty devastating and move at an incredible pace.

Fortunately, it happened in a truely replaceable piece.  Any idea what used to be mounted in that hole? (antenna or OAT sensor?)

best regards,

-a-

[Yooper Rocketman]

Looks like it started from a small spot where the paint was suspect to our lovely lead and other chemicals coming from our exhaust stream.  My IA spent 4 hours inspecting my plane on Friday (and is still not done) and made the comment how little corrosion I have had to deal with on the Rocket over the 16 year ownership.  I reminded him I've had to constantly deal with it on the bottom panels, which I suspected was the exhaust stream.  He concurred saying that was very typical, especially on the bigger bore engine airframes.  I have had to remove, clean and epoxy prime quite a few control rods, as well as the main tubular structure.  Found a few again this year that we will deal with during the engine overhaul when the Lancair is done (next annual).