Borescope inspection on a JT8D showed a cracked vane ring, three weeks later the same engine failed on the stand
I pulled the scope out after a rough run in Tulsa back in March and spotted what I thought was minor scoring, but when the teardown crew opened it up last Thursday the whole ring section had let go, so what do you guys use to tell a surface crack from a real structural issue before you sign off on a return to service?
My track record for calling cracks is about as good as my track record for picking winning scratch tickets, so take this with a grain of salt. What's worked for me is dye penetrant on anything that looks iffy, plus comparing both sides of the ring since a real structural crack usually runs deeper and shows up on both. Surface scoring tends to stay put while a bad one keeps growing every time you look at it.