WDB ON INITIAL CLB HAS NMAC WITH SMA. TCASII RA.

Narrative

A SCHEDULED WDB FLT DEPARTED RWY 9L AT PHL. FLT DEPARTED STRAIGHT OUT. EITHER LCL CTLR OR DEP GAVE US A CLRNC TO FLY RWY HDG TO 3000 FT THEN TURN L TO A NORTHEASTERLY HDG. I WAS PERFORMING THE AFTER TKOF CHKLIST AT THE TIME; BUT I BELIEVE THE HDG WAS 030 DEGS. AT APPROX 2500 FT MSL; THE TCASII WARNING SOUNDED 'TFC; TFC REDUCE CLB; TFC; TFC; REDUCE CLB.' THE RA ALERT HAD ALSO ILLUMINATED THE IVSI AND SHOWED A DSCNT. THE FO WAS FLYING. THE CAPT AND I BOTH LOOKED TO OUR L AND SAW A SMA OFF OUR L WING AND SLIGHTLY ABOVE US. THE RATE OF CLB WAS SIGNIFICANTLY DECREASED AND WE CONTINUED STRAIGHT AHEAD. AT THE TIME WE FIRST SAW THE SMA; IT WAS APPROX 50 FT ABOVE OUR L WINGTIP AND 100-150 FT TO OUR L. I COULD SEE THE OCCUPANTS IN THE ACFT. THE CAPT NOTIFIED ATC THAT WE WERE GOING TO LEVEL OFF UNTIL WE WERE CLR OF THE TFC AT WHICH TIME WE CONTINUED OUR CLB AND EVENTUALLY TURNED TO THE ASSIGNED HDG. THE PHL ATC SAID THAT THEY DID NOT HAVE THE SMA ON RADAR AND THEY MAY NOT HAVE HAD A TARGET; BUT THE TCASII WORKED AS ADVERTISED AND MAY HAVE PREVENTED A MIDAIR COLLISION. IN ANY CASE; IT WAS MUCH TOO CLOSE.