What was found
FLT NR 434, MCO-BOS AIR RETURN TO MCO, AFTER TAKEOFF THE FA INFORMED THERE WAS A STRONG BURNING SMELL IN THE REAR OF THE PLANE. PERFORMED FIM TASK 21-20-00-810-801A, NO BURNING ODOR NOTED, INSP MID AVIONICS BAYS FOR ODOR. NONE DETECTED, RAN BOTH NR 1 AND NR 2 ENG, NO ODOR NOTED BY MX, INBOUND CREW REPORTED SMELL AS NON-ELECTRICAL IN SOURCE, MORE RUBBERY TYPE, COULD NOT DUPLICATE SMELL ON GROUND AT THIS TIME, ACFT OK FOR CONTINUED SVC.