ACFT FAILED TO COMPLY WITH CLRNC TO PROCEED HEADING TO INTERCEPT RADIAL AND AS APCH CONTINUED HAS NMAC WITH SMA.

Narrative

COPLT FLYING FIRST TRIP INTO PHL. HAD BEEN CLRED TO INTERCEPT THE DUPONT 195 DEG R AND DSND TO 11000'. COPLT APPARENTLY DID NOT HEAR THE CLRNC TO INTERCEPT THE RADIAL AND OVERSHOT. CENTER CALLED AND ASKED US TO STOP AT 12000' (WE WERE AT 12500') BECAUSE THERE WAS ANOTHER ACFT AT OUR 2 O'CLOCK AND 2 MI. WE LEVELED AT 12000' UNTIL THE CONFLICT WAS CLRED UP. AT THE TIME OF THE INCIDENT; XN30 LCL TIME; WE HAD BEEN UP SINCE XA30 AM AND HAD FLOWN 5 LEGS. WE HAD ALSO HAD SEVERAL MINOR PROBS DURING THE DAY. AN FAA RAMP INSPECTION WHICH DELAYED US FOR 20 MINS IN MIA AND CAUSED SUBSEQUENT DELAYS FOR THE REST OF THE DAY; AN ENG BLEED MALFUNCTION AND A PACK TRIP (ON THE LGT). IT WAS ALSO THE COPLT'S SECOND MONTH ON THE LINE AND HIS HEADSET WAS NOT THE GREATEST SO HE WAS MISSING A LOT OF RADIO XMISSIONS. ABOUT 5 MINS AFTER THE OVERSHOOT OCCURRED AND WHILE APCHING THE ARPT AT PHL AT 7000' WE OBSERVED AN SMA ON A COLLISION COURSE WITH OUR ACFT. WE HAD TO TAKE EVASIVE ACTION TO AVOID HIM AND MISSED HIM BY ABOUT 100 YDS. THE CTLR DID NOT SEE THE TARGET UNTIL HE WAS AT OUR 5 O'CLOCK AND WE WERE ALREADY BY HIM. ALL IN ALL; NOT A VERY FUN DAY OF AIRLINE FLYING. LONG DAYS ARE BECOMING A SERIOUS PROB WITH AIRLINE CREWS AS MGMNT SEEKS MORE PRODUCTIVITY.