As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - AIR TURNBACK - 3/26/01 - AFTER TAKEOFF ON LANDING GEAR RETRACTION THE NOSE LANDING GEAR WOULD NOT RETRACT AND THE AIRCRAFT RETURNED TO ORD MAKING AN UNEVENTFUL LANDING. THE AIRCRAFT WAS MAINTENANCE FERRIED TO PHX. MAINTENANCE TROUBLESHOT AND FOUND A NOSE GEAR UP HYDRAULIC LINE CHECK VALVE FAILED. MAINTENANCE REPLACED BOTH NOSE LANDING GEAR UP LINE CHECK VALVES AND GEAR RETRACT TEST WAS NORMAL.