What was found
DURING DESCENT INTO SEA ON THE HAWKS ARRIVAL, A/C WENT OVER FMC SPEED BY OVER 20 KTS WHILE IN "VNAV PATH". A/C DID NOT REVERT TO "VNAV SPEED". GROUNDED - YES. REF 737 SYSTEMS HANDBOOK 11.030 PG 29 - UNABLE TO DETERMINE WHY A/C DID NOT REVERT TO VNAV SPEED - NOTE PER SAME HANDBOOK PAGE - VNAV "MAY" RVERT TO VNAV SPEED TO PREVENT OVERSPEED. UNKNOWN ABOVE OR BELOW 10K' AND FMC TARTET SPEED. BITE CHK'D/CURRENT STATUS DFCS'S, ADIRU'S A/T CURRENT STATUS, FMC PERFORMANCE FACTORS VERIFIED, FMC OPERATIONAL TEST PER AMM 34-61-00 GOOD. NO HISTORY.