What was found
CREW REPORTED FLAPPING NOISE COMING FROM SERVICE DOOR AREA ON CLIMBOUT. CREW RETURNED TO FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED AND FOUND A PIECE OF RUBBER DOOR TRIM FROM SERVICE DOOR FLAPPING AGAINST FUSELAGE. MAINTENANCE REMOVED RUBBER TRIM OFF OF INSIDE BOTTOM OF SERVICE DOOR AND TRANSFERRED DISCREPANCY TO DAI (DEFERRED APPEARANCE ITEM) LIST. AIRCRAFT RELEASED FOR SERVICE. MAINTENANCE SUBSEQUENTLY REPLACED SERVICE DOOR LOWER PANEL ASSEMBLY SEAL USING AIRCRAFT MAINTENANCE MANUALS AND CLEARED DAI.