As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 6229 - IAD-PHL - DURING CLIMB, MADE AN UNSCHEDULED LANDING AT IAD DUE TO LEFT RPM INDICATION FAILED. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND REMOVED AND REPLACED TACH GENERATOR. OPS CHECK OK. AIRCRAFT WAS RELEASED AND RETURNED TO SERVICE. (M)