Engine Crack or Mfg Artifact

With 200 hrs total time on the 912 ULSengine and S7 airframe, during my first annual inspection we discovered on the #4 cylinder underside, what may be a crack or casting deformity. There are no indications of exhaust leakage. The two 100-hr engine inspection compression checks were rock solid. Metal appears to “span the gap” in several places.

I sent photos (uploaded w/post) & data to Rotax in a CSIR, and am waiting on a response and guidance. Has anyone else experienced this problem and might offer some guidance on how to proceed?

Any insight is appreciated.

Picture is worth a thousand words......JImChuk

Is that a raw metal surface? it looks as though it could just be a product on the surface. dye penatrant kit is what I would be looking to try at this point. Some of it is inexpensive but I don't know the quality.

To me, it appears that the inside of the crack has the same coating in it as the exterior surface has on it. If that is correct, it left the factory that way.

Agree with Ramos - that did not develop with use - it's "original equipment Mfg Artifact" from Rotax. That stuff does happen with aluminum castings.



I am beginning to come to the unsubstantiated opinion that one of the differences between the 912 uncertified (ULS & UL) as opposed to the certified (A, etc ) may have to do with where Rotax ditches its less than perfect parts. (another person who recently reported a factory installed intake valve with an inadequate margin also comes to mind)



As to if it is a problem or not, that is impossible to determine from a photo. I think you did right contacting Rotax; and, depending on what you hear from them, your next action may be EFWD's suggestion.


Looks like the location is on the lower part of the cylinder barrel - if that is the case, you would not get an exhaust leak if it was cracked through to the inside of the cylinder - more likely the result would be oil drool since the crankcase would be under some internal pressure from normal ring blowby.


Again - just some ideas, a definitive analysis is impossible from a photo.

From a liability point of view, isn't their response going to be automatic? Something along the lines of bring it to a certified tech before going any further?

I really appreciate the feedback. I still have not heard from ROTAX and have contacted one of their local distributors (Lockwood Aviation/KSEF) who commented it did not look like a crack. He also said the aircraft is probably flyable . . . I think not. At least not until I have something more substantial. One other comment he mentioned was ROTAX likely would want the cylinder and parts/labor would be covered by warranty . . . we’ll see.

I did order a dye pen kit and will confirm what I already know in short order. Additionally, I thought I’d do a “dental mold” test to get an impression of the aberration. This is something we used to do on the Space Shuttle cold plates and critical mating surfaces. Beyond these two defining tests, I don’t know what more I can do.

Thanx again!

Robert Fisher/N719Q

Follow up for anyone interested. Dye Pen results look really promising (attached). I performed the test multiple times just to make sure my technique was correct and the results were consistent . . . no evidence of a crack. I guess I cannot believe my lying eyes.

I've had my "second set of eyes", an A&P, perform the test and results are the same. I'm waiting to hear from Rotax.

Thanx everyone for the insights.

Cheers! Fly safe.