NMAC BTWN AN MLG ON SHORT FINAL AND AN LTT DEPARTING FROM AN INTERSECTING RWY.

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I WAS THE CAPT OF AN FK100 APCHING PHL. WE WERE CLRED TO SIDESTEP TO LAND ON RWY 27L PER TWR REQUEST. KNOWING THEY WERE USING RWY 17 ALSO; AT ABOUT 400 FT AGL AS WE WERE ABOUT TO CROSS RWY 17 CTRLINE; I DECIDED TO LOOK R SPECIFICALLY FOR RWY 17 TFC. MY EXPERIENCE WITH CONFLICTS DURING PHL'S 'INTERSECTING RWY OPS' TOLD ME TO LOOK R. OUT THE FO'S SIDE WINDOW I SUDDENLY SAW THE FRONT END OF A WHITE LOW-WING TWIN TURBO PROP (300-400 FT AT ABOUT 2:30 O'CLOCK POS; SLIGHTLY HIGH) COMMUTER TYPE ACFT; BEFORE I COULD REACT THEY FLEW OVER US AND I HEARD THEIR ENG/PROP NOISE AS THEY PASSED OVER US. WE WERE ON GS TO ILS 27L. I TOLD TWR THEN AND THEY CLAIMED IT WAS ALL UNDER CTL. I DISAGREE. THE TWR SUPVR LATER TOLD ME WE SHOULD HAVE BEEN TOLD THAT THE OTHER ACFT WAS THERE; NO KIDDING. I FEEL THAT THIS IS AN UNSAFE OP AT PHL; NO MATTER WHAT PARAMETERS ARE PUT ON IT. THESE 2 ACFT CAME CLOSE TO A MID AIR COLLISION! WITH THE ARPT LIGHTING; THERE WAS NO WAY FOR US TO EVEN SEE AN ACFT TO OUR R EVEN IF THEY HAD TOLD US ABOUT THEM. THIS TFC SEQUENCING PROC SHOULD BE CHANGED -- IT IS UNSAFE!