AN ACR MLG HAD AN NMAC; OR LTSS; WITH A VFR SMT.

Narrative

DSNDING THROUGH APPROX 12500 MSL IN IDLE PWR; 300 KIAS; ON THE DUPONT ARR INTO PHL; WE EXPERIENCED A TCASII TA. TA WAS APPROX 5 NM AT 1 O'CLOCK AND 2000 BELOW. I DISCONNECTED THE AUTOPLT AND THE FO AND I VISUALLY SEARCHED FOR TFC WITH NO LUCK. AT APPROX 11500 MSL AND 2 1/2 NM WE GOT AN RA TO CLB. I IMMEDIATELY ADVANCED THE PWR AND INITIATED A 1 1/2 TO 2 G PULL-UP INTO THE GREEN ARC ON THE VVI. AFTER CLBING TO APPROX 12500 MSL; WE GOT THE 'CLR OF CONFLICT' MESSAGE AND I RESUMED THE DSCNT TO 10000 FT MSL AS ASSIGNED; EASILY MEETING ALL RESTRICTIONS. NOT UNTIL WE RECEIVED THE RA AND THE FO RPTED OUR MANEUVER TO ZDC DID WE RECEIVE ANY TFC RPT FROM THE CTLR. NEITHER PLT VISUALLY ACQUIRED THE TFC BUT AT THE BOTTOM OF OUR MANEUVER; THE RA WAS VERY CLOSE TO THE R WINGTIP OF THE AIRPLANE SYMBOL ON THE 5 NM SCREEN; AND I RECALL MINUS 04 ON THE ALT READOUT. AFTER LNDG IN PHL; PAX RPTED THAT; UPON FEELING OUR MANEUVER; HE LOOKED OUT AND SAW A TWIN TURBOPROP WITH A HIGH TAIL PASS CLOSE ENOUGH THAT HE COULD SEE BOTH PLT'S FACES IN THE COCKPIT! THANK YOU TCASII!