As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD/BOS - FLT 6510 - DURING CRUISE AT 2315 HRS ON 7-24-97, MADE AN UNSCHEDULED LANDING DUE TO RT ENGINE RPM FLUCTUATION. AIRCRAFT WENT TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND REMOVED AND REPLACED RPM PROBE. OPS CHECK OK. AIRCRAFT RELEASED AND APPROVED FOR RETURN TO SERVICE. (X)