Just found this
The white is a penetrant dye, which shows up any exhaust gases better. No gas was coming out, and no light was coming in once the section was removed.
It is being fixed immediately, by specialist “aviation approved” welding. In the meantime I will enquire about the cost from Socata, which in Inconel will be 4 digits for sure 
It was spotted by pure luck, since probably nobody inspects every corner of their exhaust so carefully…
There’s no reason to replace the part. It was welded there originally (the cracks are adjacent to an existing weld as is often the case) and assuming a quality weld repair unaffected by contamination etc, the fix will be invisible and original.
It can be difficult to do routine (preflight) inspections of exhausts. Even ours where the cowling opens up nicely with 4 dzus fasteners, you can’t really preflight inspect the exhaust until it’s so bad you have an actual hole you can feel (or you routinely use an inspection mirror every preflight!)
I was thinking of the 50hr service. Preflight, not possible, although in theory one could do quite a lot with an endoscope, on some types.
Any views on how long that tubing would have lasted? My feeling is “a very long time” otherwise there would be lots of crashes, with fires around the engine, and these cracks are not likely to be found before the next Annual. And, frankly, not even then, in most cases, unless the crack is very obvious.
I have put this pic up before, A36 Bonanza IO55B, at 2000 hours and this happened, preceded by exhaust popping closing the throttle, lucky it didnt burn through the fuel lines
I am no sure I understand the question.
First of all, in general, the risk on an NA (ie low-pressure) exhaust is low. The outflow and temperaure of gasses through a crach won’t be much (unlike TC’d) .
The risk is more of a structural failure like you see in the Bonanza above. But you need a lot of cracking to get there: if you do proper 50h inspections you will never reach that situation unnoticed.
No I would never replace an exhaust component for a crack like that @Peter, especially NA. All it needs is a reweld by someone who knows their stuff. Regular TIG with the proper inconel welding rod will provide excellent result and durability for another 1000hrs. Just make sure the inside is finsiehd properly for good gasflow. For Part 91 A&P sign-off is enough. For EASA NCO there is some debate, but most likely an 66 LMA can sign it off. Ref AC 43.13-1B ch4 sect 5
In my experience improper installation or lack of lubrication or freedom in joints is the major driver for premature exhaust crackingCan you detect that crack with a sound recording?
What I was asking is how long it might take for that crack to propagate to something serious.
That depends on the stresses at the crack (vibrations, how it is fastened etc). The crack doesn’t necessarily need to propagate at all. The exhaust gases will eventually leek through, and that could be serious.
I would certainly replace that. The tube erodes over time leaving the tube wafer thin.
Its maybe worth trying Acorn welding in Canada for a replacement, they produce new sections that are significantly more reasonable than Oem.
