B737-300 CREW ALLOWS SPD TO GET LOW WHEN AUTOTHROTTLE BECOMES DISENGAGED DURING APCH.

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CAT IIIA AUTOLAND VISUAL APCH BRIEFED. ON ARR; ON AN INTERCEPT HDG TO THE LOC; THE SECOND AUTOPLT WAS TURNED ON PER PROC. ATC WAS KEEPING US TIGHT AND ISSUING SPD AND ALT REDUCTIONS AS QUICKLY AS THEY COULD. SLOWING THROUGH 170 KTS; GEAR WAS CALLED FOR AND FLAPS 15 DEGS. ALSO LNDG CHKLIST. ATC REQUESTED 150 KTS; SO I BUGGED IT (REF WAS 151). WHILE BUGGING; VERIFYING CHKLIST ITEMS; MAINTAINING VISUAL SEPARATION WITH TFC TO FOLLOW; I NOTICED THE AUTOTHROTTLE RED ANNUNCIATOR FLASHING. LOOKED UP AT THE AIRSPD AND NOTICED 145 KTS AND SLOWING; AUTOPLT TRIMMING NOSE UP TO MAINTAIN ALT. I IMMEDIATELY THREW THE THRUST LEVERS FULL FORWARD AND PUSHED FORWARD ON THE YOKE WITH ABOUT 20-30 LBS OF PRESSURE (ENTERED CTL WHEEL STEERING). THE ACFT REMAINED ON THE GS AND REF +10 WAS RECOVERED ABOUT 4-5 SECONDS LATER. NO SHAKER OR BUFFET. REQUESTED FLAPS 30 DEGS AND LANDED WITHOUT INCIDENT. SOMEHOW; SOMEWHERE THE AUTOTHROTTLES DISENGAGED AND THE AIRSPD WAS LOST. BOTH THE CAPT AND THE CAPT JUMP SEATER NOTICED NO FAILURE. THE CAPT DID HELP OVERCOME THE PITCH FORCES AFTER I BEGAN THE RECOVERY.