PLT BECOMES DISTR DURING APCH AND FAILS TO NOTICE AUTOTHROTTLES ARE NOT ENGAGED. ACFT SLOWS BELOW MINIMUM APCH SPD.

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WE WERE W ABEAM THE ARPT AT 6000 FT; 210 KTS AND HDG 190 DEGS. I WAS THE PF. APCH CTL INDICATED THAT WE SHOULD EXPECT A SHORT APCH. WE RECEIVED A DSCNT CLRNC TO 3000 FT. I SELECTED 180 KTS; ACTIVATED THE SPD BRAKES MOMENTARILY AND REQUESTED FLAPS 8 DEGS. SHORTLY THEREAFTER I REQUESTED FLAPS 15 DEGS. I ASKED THE FO TO ADVISE APCH CTL THAT THE RWY WAS IN SIGHT. THE FO COMPLIED. APCH CTL STATED THAT A REGIONAL JET WAS AT OUR 9 O'CLOCK POS. I COULD NOT FIND THE TFC. APCH CTL STATED THAT WE SHOULD EXPECT A L TURN. THIS WAS FOLLOWED ALMOST IMMEDIATELY BY ANOTHER XMISSION DIRECTING US TO TURN L TO 90 DEGS ALONG WITH A VISUAL APCH CLRNC. THE AUTOPLT WAS ENGAGED AS WERE; I BELIEVED; THE AUTO THROTTLES. I TURNED MY ATTN TO THE FLT MODE PANEL AND DIALED A L TURN TO 90 DEGS. AS I SCANNED THE PRIMARY FLT DISPLAY; I SAW A LONG DECREASING AIRSPD TREND LINE. THE INDICATED AIRSPD WAS AT OR SLIGHTLY BELOW VMA. I CORRECTED BY SWIFTLY AND SMOOTHLY ADDING PWR. SAFE AIRSPD WAS ACHIEVED SWIFTLY. I BELIEVE THAT ALPHA MODE PROTECTION HAD ENGAGED. THE REST OF THE FLT CONTINUED SAFELY AND NORMALLY. IN MY OWN REVIEW OF WHAT CAUSED THIS EVENT; SEVERAL FAILURES ON MY BEHALF BECAME EVIDENT. I HAD DISCONNECTED THE AUTOTHROTTLES IN ORDER TO EFFECT A SMOOTH AIRSPD REDUCTION FROM APPROX 300 KTS BACK TO 210 KTS. DURING THE SUBSEQUENT DSCNT TO 3000 FT; I SELECTED THE AUTOTHROTTLES BACK ON BY ARMING THE AUTOTHROTTLES SWITCH ON THE FLT MODE PANEL. I FAILED TO ENSURE THAT THE GREEN SELECT LIGHT UNDER THE INDICATED AIRSPD KNOB WAS ILLUMINATED. BECAUSE OF THIS; I WOULD NOT HAVE BEEN SURE THAT THE SELECT MODE WAS ACTIVE. I WAS NO LONGER FLYING THE ACFT. I FAILED TO ADEQUATELY COMMUNICATE WITH THE FO THAT THE AUTOTHROTTLES WERE OFF WHEN I INTENDED THEM TO BE OFF. LIKEWISE; I DID NOT EFFECTIVELY COMMUNICATE WHEN I INTENDED FOR THEM TO BE BACK ON. I DID NOT SEEK A CONFIRMATION FROM THE FO ON EITHER OCCASION. I ALLOWED MYSELF TO BE DISTRACTED. I FAILED TO SET PRIORITIES. I WAS OVERLY INDULGED IN SPOTTING TFC. THE TFC POSED NO THREAT TO OUR SAFETY. HOWEVER; IN A MISPLACED EFFORT TO GET THE JOB DONE I ALLOWED MY ATTN TO DIGRESS FROM THE REAL JOB OF FLYING THE ACFT. I PLACED AN OVER-RELIANCE ON AUTOMATION. I FAILED TO CONFIRM MODE SELECTION OF THE AUTOTHROTTLES. I FAILED TO KEEP SCANNING. IN ANALYZING THE FAILURES THAT LED TO THIS EVENT; IT HAS GIVEN ME A GREATER AWARENESS OF THE FOLLOWING: 1) PRIORITIZATION OF TASKS. 2) CRM. EFFECTIVE COM IS SPEAKING AND RECEIVING A RESPONSE. 3) AUTOMATION. ALWAYS CONFIRM THAT THE COMMANDED MODE IS ACTIVE. CONTINUE TO SCAN INSTRUMENTATION.