What was found
BWI - FL 1950 - EN ROUTE, AT FL270, CREW RECEIVED UNSAFE INDICATIONS ON ALL THREE GEAR. ABNORMAL PROCEDURE ACCOMPLISHED, HOWEVER LIGHT REMAINED ILLUMINATED. GEAR WAS VISUALLY CHECKED DOWN AND LOCKED, AND FLIGHT DIVERTED TO BWI. FLIGHT LANDED WITH NO FURTHER INCIDENT. AIRCRAFT WAS FERRIED TO PIT. MAINTENANCE SWUNG THE GEAR. THE PROXIMITY SWITCH WAS REPLACED AS A PRECAUTION. (M)