FLC EXCEEDS SPD RESTR.

Narrative

TRAKE 8 ARR STL UNDER STL APCH CTL. THERE IS A SPD RESTR AND ALT RESTR AT KAYLA LNDG ON RWY 12L/R AT STL WHICH IS 250 KTS; 11000 FT. OFTEN CLRED DIRECT FTZ; CROSS THE KAYLA ARC AT 250 KTS; 11000 FT. IN OUR CASE; CLRED DIRECT FTZ WITH RESTRS (RESTRS NOT RESTATED). FO ENTERED WAYPOINT ABEAM KAYLA FIX WITH 250 KTS; 11000 FT. WHILE IN DSCNT PHASE WITH ZKC; 2 EXPEDITED DSCNTS WERE GIVEN. ACFT WAS BEING OPERATED IN VNAV BUT FLT LEVEL CHANGE WAS EXERCISED FOR 'EXPEDITED' DSCNT. AFTER FIRST DSCNT VNAV WAS RE-ENTERED AND ENGAGED. SAME INTENT FOR SECOND 'EXPEDITED' DSCNT BUT VNAV WAS NOT RE-ENGAGED. ACFT ENTERED ALT HOLD AT 11000 FT AND 320 KTS. CAPT; WHO WAS FLYING; SUBCONSCIOUSLY BELIEVED ACFT WAS IN VNAV. 1.5 NM PAST KAYLA ABEAM POINT REALIZED ACFT HAD EXCEEDED 250 KT RESTR. THROTTLES PULLED TO IDLE AND SPD BRAKES DEPLOYED. 250 KTS OBTAINED AT 3.2 NM PAST KAYLA ABEAM FIX. CONTRIBUTING FACTOR #1: AUTOMATION. 2 METHODS OF AUTOMATIC FLYING -- VNAV AND FLT LEVEL CHANGE WITH DIFFERENT RESULTS IF SITUATIONAL AWARENESS NOT MAINTAINED. CONTRIBUTING FACTOR #2: HEATED DISCUSSION ENRTE STL ABOUT COCKPIT PREFLT RESPONSIBILITIES. VERY DISTRACTING. FO MADE APOLOGIES IN DSCNT TO 11000 FT. CONVERSATION AND EMOTIONAL RESPONSE CONTRIBUTED SIGNIFICANTLY TO DISTR!