How To Keep Your Mooney Rust Free

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By Richard Zephro


Our fleet of aircraft is not getting any younger! While a Mooney for instance can last several lifetimes; indefinitely really;  nothing can last and last without proper maintenance including ourselves.

A recent reminder of that came with removing the interior panels for refinish on Mike Dugger’s recently acquired 1980 Mooney 231 Turbo. This is a relatively young (time-wise) airframe and had just received a thorough annual inspection by Dugosh in Kerrville.

They had inspected the tubes in the “normal” places and pronounced the airframe as “healthy”. We agree as it was obvious that someone along the line of ownership cared about the tubes and had them inspected and coated with an epoxy finish. Cool! But what was not checked by Dugosh and obviously every other inspector since this Turbo Mooney was new? The UPPER TUBES!

Those of us close to “MOONEYDOM” are used to inspecting the lower tubular structure because that is where the rust usually begins which was the reason and need for Mooney to have come out with the 208 A&B Service Bulletins years ago in order to preclude the advent of RUST on and in the tubular structure of each Mooney ever manufactured.
OUT OF SIGHT, OUT OF MIND…..

Okay; removing the ceiling panel of a Mooney (especially the later models that have air vent tubes run along the ceiling) can be anywhere from a bitch to a nightmare to R&R. However when we do an interior refinish including the ABS interior panels, we are one of the few who ever have to remove those ceiling panels. Doing so exposes the upper “roll cage” tube structure. Those upper tubes do more than protect the occupants from a roll-over type accident, the center most tube actually supports the weight of the engine! Cut that tube or allow it to rust away can lead to losing your engine (and I don’t mean a power loss!) I’m talking LOSE YOUR ENTIRE ENGINE! To be fair, there has never been such an accident in Mooney aircraft due to rusted upper tubes, but will you want to be the first one to try that?

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What caused this RUST on an otherwise non-corroded airplane? CONDENSATION! Years of changing ambient temperatures causes condensation (moisture) that has affected the upper tubes above and rust has set in for years that has gone unnoticed.

I placed a call into Ronnie Kramer at Dugosh and told him about what I had discovered and to Dugosh’s credit, Ronnie was over to my airport in a flash to take a look. Fortunately the rust was only in a state of surface and once cleaned and re-zinc chromated, the tubes were unharmed and the fix was easy. Had the rust have penetrated the upper thin tubes, then major alteration by cutting and re-welding new tubes in the affected area would have become necessary.

While water cannot get into the upper tubes via a leak somewhere, condensation is enough to have the need to check those upper tubes now and at least every 5-10 years subsequently.
The JOB!

It wasn’t until 1979 with the advent of the Mooney M20K-231 that the factory began to use the way nicer NACA scoop fresh air vent system. If memory serves, that system also became standard on the Mooney 201 in 1981 or 1982. If you have the NACA type vent system, expect the work to be “labored” at best. There are wires, speakers, vent controls, lighting, etc. within those ceiling panels in addition to the cumbersome vent tubes that run along the ceiling. It was all put together by the Mooney Factory as if no one would ever have to remove that 2 piece ceiling panel. You need to be a midget octopus in order to get everything back in place in order to re-install the ceiling panel, but if I can do it; so can you (or your mechanic).
On earlier Mooneys, the job was not all that difficult because less was attached to the ceiling on those models, but it is still an exercise in twisting gymnastics to re-install.

To remove the ceiling panel you must first remove the ABS window frame panels. Armed with your small Philips screw driver and some pliers and Allen wrenches, you can at least drop the ceiling if not removing it completely in order to check for rust at the upper tubes. Of course if you find any rust forming on those tubes, then you will have to completely remove the ceiling panel.

Emory cloth or Scotch Bright are useful in removing the rust. Once the surface rust is cleaned off of the tubes you can then inspect them for any areas the rust may have actually penetrated the steel ceiling tubes. If even slight pitting is evident, you should then turn the job over to a professional in order to determine if the tubes in that area will need to be cut out and new tubes (or tube sleeves) are called for.

There is so much that you as an aircraft owner can do in order to keep your airframe young by Preventative Maintenance Practices. Flying is more than a simple hobby, but making ownership YOUR HOBBY may re-direct your daily efforts to the more worthwhile or deserving hobby by making your personal airplane as safe an endeavor as it can be. Remember; you take your family and friends with you up, up, and away, and it is YOUR RESPONSIBILITY to know what’s going on between the paneled walls of your airplane. We recently did an interior in what appeared to be a clean and “well maintained” Cessna 172. Those wall panels had never been removed and I was aghast to discover the rusted cable and pulley that operates the Cessna’s ailerons! I showed the owner and he was shocked having just purchased the bird and seeing it through an “extensive” pre-purchase inspection. GET TO KNOW YOUR AIRPLANE INTIMATELY!

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