What was found
FLT#981, BOS-TPA. 'DESCENDING THROUGH 4,000 FEET, FA #4 REPORTED A VERY BRIEF DIRTY SOCK SMELL THAT DISSIPATED QUICKLY; BRIEFED FLT CREW AND INFLIGHT CREW. EXAMINED MX-270 AND DETERMINED ODOR LEVEL 1 TRANSCEINT DUE TO ENVIRONMENTAL SYSTEM ODORS. APU ALREADY DEFERRED UNDER MDDR# 506972 TO CORRECT THE CAUSE OF ODORS IN THE PAST. ODOR WAS NOT PRESENT. "COMPLIED WITH INFORMATION NOTICE 2017-T015 SECTION A ISOLATED TUPE 10,(A),1C PER TSM 05-50-00-810-085/B/TSM 05-50-00-800-085-D. THE AIRCRAFT IS OK FOR SERVICE.