What was found
RDU - FL 607 - IMMEDIATELY FOLLOWING ROTATION, DURING GEAR RETRACTION, THE FLIGHT CREW HEARD A LOUD BANG NOISE FOLLOWED BY A VERY LOUD RUSH OF AIR. THE FIRST OFFICER OBSERVED AND OBJECT TO GO PAST THE WINDSCREEEN. CREW ASSUMED IT WAS A BIRDSTRIKE AND RETURNED TO FIELD AT RDU. FLIGHT LANDED WITHOUT FURTHER INCIDENT. NO EMERGENCY WAS DECLARED. MAINTENANCE INSPECTED AIRCRAFT FOR BIRDSTRIKE. NONE NOTED. FOUND LINK ASSEMBLY ON LEFT NOSE GEAR DOOR BROKEN. REPLACED SAME AND ADJUSTED LINKAGE PER MM 32-33-61. GEAR SWING AND OPERATIONAL CHECK GOOD. (M)