Plugging holes in the gear

jetguy · Post by **jetguy** » Wed Jul 17, 2013 7:36 pm

Finally removed the chrome "steps" that someone had previously installed on the main gear legs. I've never been a fan of drilling holes in spring gear legs, but nobody else seems to think it's a big deal. Now that the steps are gone the visible bolt holes are quite unattractive, to say the least, and I'd like to plug 'em, but with what? Thoughts range anywhere from pressing in some bronze round-stock to filling with epoxy or plugging with a rivet or....just leaving them alone. Any good ideas?

bagarre · Post by **bagarre** » Wed Jul 17, 2013 9:30 pm

I think you might have a pair of un-airworthy gear legs on your hands as I don't think there is any approved method to drill a hole in a gear leg. Was it done via an STC or some other data?

If it was mine and I chose to fly on them, I'd clean the holes real well, radius the top and bottom and put a thin coat of white paint on it so I could very easily check for cracks.
And make it part of my preflight inspection list.

Wed Jul 17, 2013 11:03 pm

Lots of Cessna spring gear, including the originals found on the '48, have holes drilled into and through them for various reasons. So while David might be technically correct in the strictest sense of legality on a 170, the holes don't necessarily make the gear unsafe.

To plug them my thoughts are to use something that won't draw attention to it like airplane type hardware which is easily accepted when found on an airplane correct or not. So I would use airplane hardware, more specifically a rivet.

c170b53 · Post by **c170b53** » Thu Jul 18, 2013 12:23 am

I'd clean them, 10x them then fill with PRC aerodynamic class sealant. If you really want to remove all doubt them have them mag particle inspected first.

jetguy · Post by **jetguy** » Thu Jul 18, 2013 4:41 am

OK, good suggestions. Did I mention they're 180 gear legs? I imagine the extra beefiness helps somewhat.
George? Anyone seen George? Probably on vacation.....

Post by **GAHorn** » Thu Jul 18, 2013 9:26 am

Hello, Greg!
Yep...I'm on my way to convention, overnight in AR.
As for the gearlegs,....I've never been a fan of the 180/185 gearlegs on a 170 unless one is operating with a heavier engine conversion or operating on "off-airport" sites and need greater ground-clearance, etc..
Bruces observation about 48 model gearlegs being already "drilled" does not address the fact those are part of their pre-annealing process. Subsequent cutting/drilling would stress the spring and require an approval basis.
In any case, I think you will find that Cessna will not approve any drilling of holes in the gearlegs. (In fact, there have been numerous cases of drilling/cutting/welding which have proven disastrous to spring gear legs, and such work is almost always/universally condemned.)
However, if you do keep them in-service, the inspection process suggested by Jim is a good one, and so is radiusing of the holes edges (prior to the inspection). The holes can be a starting-place for cracks and heavy paint, especially epoxy/enamel types, may hide a crack propagating beneath the paint. A rivet will expand to FILL the hole and add stress to it. (For that matter, so does a bolt because as the spring flexes, the rivet or bolt will offer a resistance to "crushing" that will be additional impetus for starting a crack.) The flexible PRC sealant is the better method if you decide to go that route, but unfortunately that will also tend to hide any crack propagation. (I suspect the intent of Jim's solution is to disguise the improper alteration and reduce any notice by critical eyes.....which, if correct, hints that the majority of observers will also feel the gear is not airworthy.)
If a crack does appear, it will be critical to discover it early or it can lead to the loss of the airplane and possible serious injury/etc. to occupants.
Then there is the question of why the holes were drilled for steps to begin-with.... Does your airplane have boarding steps? Or were they removed? Will you have to install steps?
The very BEST action for you in my opinion is to replace those gearlegs with serviceable units.
I believe if a conscientious inspector sees them as they are (or even if they are "filled", etc.) he will condemn them, and you may be stuck wherever that may be.
Sorry not to have a better answer for you.
Kind and sympathetic regards,
George

c170b53 · Post by **c170b53** » Thu Jul 18, 2013 3:01 pm

The holes themselves would not be my worry (depending on location). If a crack has not developed, then likely you'll not have problems in the future but much like sound legs, ongoing condition, usage and care will dictate when replacement will occur. I suggested PRC as its pliable and will expand and contract with the gear to maintain a seal to prevent corrosion. Likely your gear's downfall will be corrosion, which will likely be the initiation cause of a crack to form from those bores.

bagarre · Post by **bagarre** » Thu Jul 18, 2013 3:18 pm

My comments were from an approval point of view, which will probably ground the airplane sooner than the structural concern.

For corrosion, wouldn't a decent prime and paint of the hole serve better than plugging it?
Seems like a plug of any kind (including a rivet) would have the potential to trap moisture.

You could always fill it with a MIG welder and grind it smooth

(Kidding, that would do more damage than the hole itself)

bigrenna · Post by **bigrenna** » Thu Jul 18, 2013 4:02 pm

delete

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