A&P says (In connection with a Continental O200 top overhaul) the crankshaft has too much rust between engine housing and propeller (outside engine). I'm thinking the crankshaft diameter reduction and strength reduction from rust is less than 1% and irregular distributed over the length and diameter. The design strength of the crankshaft has likely a 50 % safety factor. So there should be no problem. Here are the photos: http://hc-research.com/Continental.html What do you think?
Well ..... Continental service bulletin SB09-14 addresses this subject. Go to Continental Aerospace Technologies, support, service bulletins to read a copy.
Thanks Eric, I have seen the service bulletin.
But I am unhappy taking out engine and crankshaft because the 50% safety factor is now a 49% safety factor.
Where did you come up with the 49% number?Originally Posted by Firefly
I don't know how you figured that.
You asked what do others think.
I think you've got a area corrosion that circumferences the crank shaft and is a excellent point for cracks to begin. I'm guessing you've got the issue cleared up by now.
Care to share how it was handled?
After reading the Service Bulletin, and judging by your pictures, I am in agreement with you A&P. Repair or replacement is in order.
Your A&P is correct. It isn't the reduction in area of the crankshaft that's the problem, but the rust pitting creates stress risers where the crankshaft has a greater likelihood of cracking and eventually failing all together. As a point of comparison, check the Lycoming service bulletin/FAA AD regarding corrosion pitting on the inside of the crankshaft bore on Lycoming engines (Lycoming SB 505). Those cranks get failed for significantly less corrosion than is shown in your photos. Yours can be reground to remove the pitting and returned to service.
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