As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GENERAL ELECTRIC STARTER GENERATOR (PN 2CM308C3) WAS INSTALLED ON OUR APU ON 10/30/01 WITH A NEW SPLINE SHAFT SHEARED AT THE BASE OF THE INTERNAL SPLINE AFTER ABOUT 50 START CYCLES. IT IS OUR OPINION THAT THE HOLE, WHICH IS DRILLED AND TAPED TO ACCEPT THE RETAINING SCREW IS BEING DRILLED TO DEEP AND IS THE CAUSE OF THE SHAFT FAILURES.