I know many of you have your own birds and most probably do some maintainance on your own ships.
My Bi Plane, Marquart Charger, has an IO-320-B1A engine.
That engine and many 320 Lycomings have an AD, 98-02-08, that requires an inspection of inside of the business end of the crankshaft.
Not a bad process in itself but kind of a pain in the tailfeathers.
On mine, since it had only 1000 hrs since rebuild, was due for the first look see.
Pulled the freeze plug, cleaned all of the 1000 hours of sludge out of the bore, cleaned up the bore and inspected for corrosion.
Looked great!!!! (Good oil and regular changes helps to keep the bad stuff burned away, I hope)
With the AD is a form that has to be filled out and sent to the feds.
That form required ser. no. and part no. off the crank.
In the process of trying to find these numbers on the prop flange I noted some interesting marking on the webs between the lightening holes on the rear side of the flange. With a tight feeling in my gut, I commenced to clean up the back and front side of the flange with scotchbrite.
Once all was cleaned up and nicely shiney, the knot in my gut was quite a bit larger.
The marks were CRACKS!
There are six lightening holes, the webs are between the holes.
THREE adjacent webs had cracks hole to hole on the back side!
The center web was cracked to visable on the front side!!!!
My Crank was scrap!
Once I thought it out and figured better found now on the ground that when upside down or with the nose pointed straight up.
NEW Lycoming crank is on the way.
Crankshaft guru at Poplar Grove Airmotive told me that the crank in my engine was a very OLD seris crankshaft and was lighter than the new one will be. I hope the new one has a solid flange!!!!
SOOOO........Next time you have the prop off your bird, take the time to remove all paint and crud from the flange, both front and back, and take a REAL CLOSE LOOK for anything that might be a crack.
My cracks were pretty hard to see, smaller than a human hair.

Hopefully none of you will find anything but remember, that little flange is what keeps the wind blowing in your face and without it and the attached propeller, you might experiance the wind hitting you in the BACK of your head as you plummet rearwards towards the ground to that terrible hard stop at the end.

Take this seriously!
If you pay to have your work and inspections done, INSIST that the flange is inspected!