BE58 PLT LOSES SITUATIONAL AWARENESS DURING APCH TO BWI.

Narrative

I HAD BEEN CLRED BY APCH TO DSND FROM 9000 FT AND INTERCEPT THE RWY 15 LOC AT BWI. I FLEW THROUGH THE LOC AND MISSED 2 CALLS FROM APCH. THIS RESULTED IN APCH HAVING TO RERTE 2 OTHER ACFT. THE WX IN THE DC/BWI AREA WAS DETERIORATING; WITH CEILINGS LOWERING RAPIDLY; VISIBILITY DROPPING BELOW 2 MI; AND SNOW. I HAD PICKED UP LIGHT/MODERATE ICE DURING THE INITIAL DSCNT FROM 13000 FT AND OBSERVED THAT THE L ALTERNATOR WAS NOT INDICATING THAT IT PICKED UP ANY LOAD. THE 'ALTERNATOR OUT' WARNING LIGHT WAS NOT FLASHING. IN THE PROCESS OF ANALYZING THE ELECTRICAL ISSUE; AND PICKING UP THE ATIS; I LOST TRACK OF HOW FAR PAST THE WESTMINSTER FIX I WAS. AS A RESULT; WHEN APCH CLRED ME TO 3500 FT; AND TO INTERCEPT THE RWY 15 LOC; AND ASKED ME TO PICK UP THE JUST POSTED NEW ATIS; I DID NOT ESTABLISH A RATE OF DSCNT NECESSARY TO COMPLY. FURTHER; IN LISTENING TO NEW ATIS; LOADING THE APCH FOR RWY 15 IN THE GPS; AND CONTINUING TO MONITOR PARTS OF THE ELECTRICAL SYS; I MISSED THE 2 CALLS FROM APCH. (I HAD TURNED THE VOLUME UP ON THE SECOND COM TO BETTER HEAR THE ATIS.) WHEN I PUNCHED THE #2 COM OFF; I HEARD THE CALL FROM APCH ADVISING ME THAT I HAD BEEN OFF THE AIR AND MISSED HIS CALLS. I WAS SURPRISED; AS COM #1 HAD BEEN ACTIVE THE ENTIRE TIME; BUT AT THAT POINT; I ALSO REALIZED THAT I HAD FLOWN THROUGH THE LOC. THEN I KNEW I HAD BEEN SO PREOCCUPIED WITH THE ATIS (GREATLY DETERIORATING CONDITIONS TO 400 FT; 1 MI AND SNOW); AND WATCHING THE ELECTRICAL LOADS; THAT I HAD NOT REALIZED HOW CLOSE I HAD BEEN TO THE EXTENDED LINE OF RWY 15 WHEN INSTRUCTED TO DSND FROM 9000 FT TO 3500 FT. THE APCH TERMINATED IN A LNDG ON RWY 15. WHILE TAXIING TO THE FBO; THE L ALTERNATOR INDICATED THAT IT WAS PICKING UP THE APPROPRIATE SHARE OF LOAD. ON THE RETURN TRIP TO BNA; THE L ALTERNATOR AGAIN SHOWED THAT IT WAS NOT CARRYING LOAD. HOWEVER; DURING GND TESTS ON THE NEXT DAY BY THE FBO; BOTH ALTERNATORS TESTED AS CARRYING LOAD. I HAD FLOWN VERY LITTLE; ABOUT 30 HRS; IN THE PAST 90 DAYS; ALTHOUGH THIS INCLUDED RECURRENT TRAINING IN LATE JANUARY. THE 4 TRIPS HAD BEEN LONG HAUL XCOUNTRY; AND FLOWN UNDER IFR FLT PLANS. IT HAD BEEN 32 DAYS SINCE MY PREVIOUS FLT. I HAD NEVER FLOWN INTO BWI BEFORE AND; THEREFORE; WAS NOT FAMILIAR WITH HOW THE INCREASED SECURITY MEASURES MIGHT AFFECT OPS. I KNEW I WAS A LITTLE RUSTY; AS MY RECENT FLYING HAD ALL BEEN 3- AND 4-HR LEGS TO PLACES I HAD BEEN MANY TIMES AND IN GOOD WX. UNDER THE STRESS OF A POTENTIAL ELECTRICAL PROB; IN CLASS B AIRSPACE; AND NEXT TO THE DC AIR DEFENSE ZONES; WHILE ATTEMPTING TO LISTEN TO 2 RADIOS; PROGRAM THE GPS; DSND; AND INTERCEPT A LOC; WHILE FLYING IN IMC WITH ICE; I FELL INTO THE TRAP OF BECOMING OVERLY FOCUSED ON PARTS OF THE TASK; AND LOST SITUATIONAL AWARENESS. ALL OF THIS SHOULD HAVE BEEN MANAGEABLE; AS EVIDENCED BY THE ULTIMATE OUTCOME OF A STABLE APCH AND LNDG. HOWEVER; WHAT WAS MISSING WAS THE ABILITY TO PROPERLY PRIORITIZE; AND STAY FOCUSED ON JUST FLYING THE APCH. THE ICING WAS NOT A CRITICAL PROB BELOW 9000 FT; AND THE R ALTERNATOR WAS DEFINITELY WORKING. I SHOULD HAVE TOLD APCH THAT I WOULD NOT BE ABLE TO GET THE UPDATED ATIS IN TIME; GIVEN THE VERY SHORT DISTANCE TO THE LOC AND SINGLE PLT OPS; RATHER THAN RISK MISSING COMS. BEING A LITTLE RUSTY JUST ADDED TO MY INEFFICIENCY; SUCH AS NOT DIALING IN THE LOC ON THE #2 NAV SOON ENOUGH OR SWITCHING THE GPS TO VLOC AS SOON AS THE PROC WAS ENTERED. PREVENTION: A MENTAL CHKLIST WHEN WORKING ON A NON ROUTINE FLT ISSUE; SOMETHING ALONG THE LINES OF: 1) FLY THE PLANE. 2) WHAT'S MOST IMPORTANT RIGHT NOW? 3) RELAX. 4) REPEAT STEPS #1-#3 ABOVE.