As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DCA - AFTER TAKEOFF, CREW WAS UNABLE TO RETRACT THE LANDING GEAR AS THE LANDING GEAR HANDLE WOULD NOT RAISE. CREW DECLARED AN EMERGENCY AND RETURNED TO THE FIELD AT DCA. FLIGHT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND THE LANDING GEAR LATCH AND PRESSURE WARNING CIRCUIT BREAKER TRIPPED. RESET CIRCUIT BREAKER AND PERFORMED LANDING GEAR LEVER LOCK SYSTEM CHECK PER TSM 32-31-21. OPERATIONAL CHECK GOOD. AIRCRAFT OK FOR SERVICE.