HDG TRACK DEV. NMAC.

Narrative

UPON ENTERING CLASS B AIRSPACE; WE WERE AT 6000 FT MSL. WE WERE TOLD TO EXPECT RWY 28R VISUAL FOR LNDG. APCH WAITED UNTIL WE WERE 8 MI FROM THE ARPT BEFORE GIVING US A LOWER ALT (2500 FT MSL). WE TOLD THEM WE WERE UNPRESSURIZED AND THAT WE COULDN'T GET DOWN IN TIME. WE WERE THEN GIVEN A TURN AND TOLD TO EXPECT RWY 32; WHICH WE COULDN'T GET DOWN FOR EITHER. ATC THEN TOLD US TO FLY 120 DEGS. ATC THEN DECIDED TO PUT SOMEONE ELSE IN FRONT OF US. ATC THEN TOLD US TO 'BEND IT AROUND AND EXPECT RWY 28R VISUAL.' WE KEPT TURNING AND WATCHING THE TFC ON TCASII. PAYING ATTN TO THE TCASII AND LOOKING OUTSIDE; WE TURNED PAST 120 DEGS BY THEN TCASII GAVE US AN RA WHICH WE OBEYED. IN THE FUTURE; I THINK ATC SHOULD TAKE INTO CONSIDERATION THAT SOME ACFT ARE NOT PRESSURIZED. ALSO; THAT IN POOR VISIBILITY IN HAZE WE DEPEND ON ILS'S TO BACK UP OUR VISUAL APCHS. WHEN ATC CHANGES RWY ASSIGNMENTS 3 TIMES IN A PERIOD OF 5 MINS IT MAKES IT VERY DIFFICULT TO SET UP RADIOS FOR APCHS. TOO MANY DISTRS! IN THIS INSTANCE TCASII WAS CRUCIAL IN MAINTAINING SEPARATION. IT HAS PROVED MANY TIMES OVER INVALUABLE.