Cracked main gear found during annual

[Mark942]

Let us know what Savvy has to say.  Photos can be deceiving, and not under a Black Light, but looks to me like a defect in the paint and a bit of rust under the paint crack leaching out.  I've seen a lot of cracks in medical orthopedic devices that are penetrant inspected.  That looks like micro welding inconsistencies to me that have been there since manufacture.  I agree with others that swapping it out for a salvage unit is not value added.  Please keep us posted, and best of luck.

-mark 

[65MooneyPilot]

They should have stripped the paint off before inspecting it. That way you know you are looking at the metal, not cracked paint. If it is really cracked you will be able to see it with the famous 10X magnifying glass. That is not cracked.

[Stubby]

Can they strip the paint and perform an MPI inspection? That seems like the most logical and effective way to diagnose a problem such as this.

[rbmaze]

I'm going to see if the paint can be stripped. How is this typically done? Will the gear need to be removed first?

It looks to me like an abrasive was used and it took off some paint but not all of it, or left a primer.

I've never heard of MPI inspection. 

[47U]

3 minutes ago, rbmaze said:

I've never heard of MPI inspection.

Magnaflux.

The shop did remove some paint, at some level.  It didn’t necessarily look (to me) like bare metal, but overexposure with the closeup flash might have washed out the image, appearing as some coating still remained.  Inconclusive.  

Maybe some paint still does remain, but if the shop is removing paint to support the dye penetrant, then I’d think they’d remove enough to make the inspection viable.  

That’s why I like to see the crack under the black light.  It might be cracked, or it might be a portion of the weld bead did not penetrate the tube, appearing as though it’s cracked.

[Joshua Blackh4t]

Am I the only one who thinks that its a non-issue due to it only being landing gear?

It has 2 potential modes of failure IF it is a crack:

Slowly stress cracking which will be noticeable well before it fully fails

Or being the weakest point and breaking in a significant hard landing. With such minor cracking it would need to be a very hard landing that would hurt other things anyway.

With either failure mode, there is neglegible danger to the people. 

Since it can only fail on the ground, asses it like you would for a car. Sure, an expensive car, but one that only drives 100km a year. 

[Kelpro999]

12 hours ago, Joshua Blackh4t said:

With either failure mode, there is neglegible danger to the people. 

 Exiting the runway at 75 can be catastrophic.

[PT20J]

IA amongst us can comment, but I don't think mine would consider a gear leg with a crack airworthy (if it is a crack, of course).

[EricJ]

9 minutes ago, PT20J said:

IA amongst us can comment, but I don't think mine would consider a gear leg with a crack airworthy (if it is a crack, of course).

Yeah, that weld is there for a reason.   You don't need any floppy elements in the gear leg.    IMHO the question is just whether it is a crack or not.    I haven't seen anything I'd consider reliable evidence of a crack.   That dye pen evidence posted in the pics doesn't seem to show a crack as far as I can tell.

I've recently seen similar posts in various FB pages that seem to indicate at least some shops have forgotten how to use dye penetrant for inspection.   I get the impression that some people just use it as a tool to convince customers that they need repair work done.

[Joshua Blackh4t]

5 hours ago, PT20J said:

IA amongst us can comment, but I don't think mine would consider a gear leg with a crack airworthy (if it is a crack, of course).

I can't talk for the GA world, but in recreational/ultralights, it would not be uncommon that an undercarriage got a tiny crack during a really bad landing, and the owner decided to continue flying and keep an eye on it.

 

Yes, failed undercarriage CAN be catastrophic, but likely wont be. Add in that its also not likely a crack will fail, and its not even likely it IS a crack.

This adds up to a very low risk for continuing to fly and monitoring the suspected crack. 

[Matthew P]

IF it is a crack, reach out to Don Maxwell as he repaired (cutout/rewelded and heat treated) my nose gear....does excellent work and price was reasonable..,

[highflyer77]

Joshua, it´s absolutely up to you how you do your personal risk assesments. If you  consider veering off the runway at high speed due to a failing (main) landing gear with all subsequent possible movements/decellerations/ascellerations is a minor risk, feel free to continue in your personal process of risk assesmant. But keep in mind: our birds have no airbags, no sidebags, no crumple zones etc. like modern cars. Furthermore, keep in mind, there always could be hard obstacles in your way that end in bad collisions causing bad and serious, even deadly injuries. Still no problem to me, if you continue considering this as a small personal risk for you.

But as soon as you decide to take anybody else aboard as your passenger (it might be your spouse, or your child, or both ... or "just" a good personal friend to whom you are doing a favour by giving him a personal ride in your plane to a distant city he needs to go), please do me one favour: please re-evaluate the initial situation for your risk assesment and consider it thoroughly !

Concerning the crack: there´s only one way to be sure: it needs further investigation; either by removing the paint and doing another thorough inspection by using dye-penetrant means again, or maybe by means of some magnet-inductive testing... I would not change the part against a used other one as long as I am not sure if there´s a crack or not.

Just my 2 cents, I am not a A&P etc. ...     

[Joshua Blackh4t]

5 hours ago, highflyer77 said:

Concerning the crack: there´s only one way to be sure: it needs further investigation; either by removing the paint and doing another thorough inspection by using dye-penetrant means again, or maybe by means of some magnet-inductive testing... 

Personal risks aside, please don't ever be SURE of anything on your plane.

Keep monitoring everything from your engine to paint chips to intercom static and make continual judgements on what is safe. If we were ever sure we'd never need to do a pre-flight, or practice forced landings, or have alternates.

Back to the landing gear. You've done the test of "we landed on it for many years and there is only a hint of a possible crack", now you could do "we are still landing on it and nothing is getting worse". Both are very good tests for metal stress cracking. 

 

[rbmaze]

I have an update to share. It turns out the gear really is cracked. I had a magnetic-particle inspection performed last week and it revealed several cracks in the area.

Neither Don Maxwell nor LASAR are able to repair this, so I am moving forward with the salvage gear. I will have an MPI performed on this one before installation to verify it is a good part.

[65MooneyPilot]

Well I am glad that you continued your investigation. Did the inspector strip off the paint to inspect the area? Now you can move forward. Excellent job!