As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE TOWER NOTIFIED CREW THAT SPARKS WERE COMING FROM THE NR 2 ENGINE WHILE ON APPROACH TO BOS. THE AIRCRAFT LANDED WITHOUT INCIDENT. THE NR 2 ENGINE WAS REMOVED AND REPLACED. INVESTIGATION REVEALED THAT THE PRIMARY CAUSE OF ENGINE FAILURE WAS DUE TO A BROKEN C-7 BLADE.