As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 6418 - IAD-BOS - DURING CLIMB-OUT RETURNED TO IAD DUE TO THE LANDING GEAR NOT RETRACTING WHEN SELECTED UP AFTER TAKEOFF. AIRCRAFT RETURNED TO IAD WITH NO FURTHER INCIDENTS. MAINTENANCE REPLACED THE LANDING GEAR CONTROL UNIT. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (W)