original post by megan
Certainly going to be interesting to see the root origin of the failure.
Reminded of the fan disc failure in a DC-10. Was found the disc had been machined from a piece that came from the near end of a billet, which was found to contain inclusions. Fix, discard the ends of the billet.
In the early 60's worked in a shop manufacturing steam turbines for ships. For the gear cutting shop battery back up was supplied to the cutters/grinders. Once a cut/grind on a tooth was begun it was not permitted to be interrupted, for it introduced a point of future failure.
original post by riff raff
Lots of reports to read regarding this issue. Interesting that AH says one planet gear design has better reliability than the other. Yet they have not established the root cause of the planet gear that failed. If the root cause was a manufacturing problem, all of the planet gears and bearings would likely need to be replaced again.
My thinking too ... the other day I pulled some numbers out of the air .... fleet of 200 machines X 8 planetary gears = 1,600 gears .... changed every couple thousand hours there could be way over 5000 of those gears manufactured and only 1 would have to be off-spec and fail
Hopefully someone more knowledgeable on total-fleet-hours and total-gears-manufactured can improve my numbers .