Pretty bad. Definitely not airworthy in the Certified world. That is the thrust surface for a tractor configured engine, the prop is always pulling the crank against that surface. Having said that I have seen guys run pitted cranks like that in experimental’s. Likely hood of failure is very low in my opinion but it’s not what I would recommend. You can do some minimal grinding in this area depending on your thrust clearance. Wouldn’t hurt to have AEA out of Dallas take a look and see what they can do for you.
i wonder how many of us are flying around with similar crankshaft pitting, not knowing there is any.
besides splitting the crankcase... how to detect that? could surface pitting be seen as debis in the filter?
i wonder how many of us are flying around with similar crankshaft pitting, not knowing there is any.
besides splitting the crankcase... how to detect that? could surface pitting be seen as debis in the filter?
to answer the OP's question...
remembering the metallurgy lectures i got when i looked 25 years younger and 25 kg lighter...
i am not the designer of the crankshaft but i believe that our crankshafts are made of soft and flexible steel alloy, surrounded by a hardened surface. to harden a steel surface you implement carbon atoms into the crystalstructure of the metal. these carbon atoms usually don't go very deep into the alloy, so corrosion and pitting could easaly eat in deeper then the hardened surface actually is. that could (most likely) affect everything including strength, fatique life and corrosion resistance. all these parameters, carefully engineered by the manufacturer, are kinda important when it comes to crankshafts of aircraft engines.
grinding/sanding away these spots will most likely not improve anything.
another thing with pitting is that it will never get better. if you reuse the crankshaft it could become much worse in a matter of minutes/hours.
long story short: this crankshaft has to see some really knowledgable expert on the topic before any further use. your local AP will usually not be sufficient enough to make a solid judgement.
but that's all my very personal opinion only.
Internet opinions are interesting, but the most complete answer will come from a place like Aircraft Specialties (http://www.aircraftspecialties.aero/), the folks in Tulsa that overhaul and certify cranks. I’m guessing that with that picture, they can give you a definitive answer pretty quickly.
Paul