As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO SFO DUE TO NR 1 ENGINE FAILURE. *S/D* STAGE 4 BLADE FAILED IN FATIGUE IN ROOT ATTACHMENT AREA, LIBERATING AIRFOIL AND PLATFORM AND CAUSING EXTENSIVE DOWNSTREAM DAMAGE. THE MANUFACTURER HAS ISOLATED THE CAUSE TO A VSV SCHEDULE INTRODUCED WITH EEC SOFTWARE CHANGE NR 11. EEC SOFTWARE WILL BE REVISED TO REVERT TO PREVIOUS VSV SCHEDULE. A SERVICE BULLETIN IS EXPECTED IN APRIL OF 2000.