As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 6548 - IAD-SCE - AIRCRAFT MADE A UNSCHEDULED LANDING AT IAD DUE TO LEFT RPM GAUGE FAILURE. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND REMOVED AND REPLACED TACH GENERATOR. OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)