MDT CREW HAD LESS THAN LEGAL SEPARATION IN C90 CLASS B AIRSPACE.

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BEING VECTORED BY LGA APCH; ON R DOWNWIND TO INTERCEPT LOC RWY 31 APCH. WINDS 340 DEGS AT 20 KTS GUSTING TO 30 KTS. CTLR GAVE US A R TURN TO 220 DEG HDG. ON TCASII IT LOOKED LIKE HE WAS TRYING TO GET US BTWN 2 ACFT ON FINAL 5 MI APART. WE MADE TURN; BUT BY THE TIME THE AUTOPLT SWUNG THE ACFT AROUND AND THE WIND PUSHED US (WINDS AT 2000-3000 FT WERE 40-50 KTS) WE WERE HEADED DIRECTLY FOR THE SECOND ACFT; SAME ALT AS US; 2000 FT MSL. WE GOT A TA ON TCASII. CTLR GAVE US AN IMMEDIATE CLB TO 2600 FT. WE CLBED; THEN VECTORED ACROSS LOC; ANOTHER VECTOR TO R; TO INTERCEPT AGAIN. THE CTLR ASKED US IF WE HAD ACFT IN SIGHT. I SAID WE DID. WE HAD 1.5 MI SEPARATION; THEN HE CLRED US FOR THE VISUAL AND DUMPED US ON TWR. WE CONTACTED TWR. TWR ASKED 'DO YOU HAVE THE ACFT AHEAD IN SIGHT?' I SAID 'YES; BUT I DO NOT KNOW WHAT WE ARE DOING HERE.' THE TWR TOLD US TO GO AROUND AND CLBED US TO 3000 FT. BACK WITH APCH; THEY GAVE US THE SAME 220 DEG HDG AS THEY SWUNG US BACK TO INTERCEPT AGAIN. WE LANDED WITH NO FURTHER CONFLICT. I'M PRETTY SURE THAT FO AND I WERE CORRECT WITH THE HDGS FLOWN. WE QUERIED EACH OTHER AND AGREED 220 DEGS WAS THE ORIGINAL ASSIGNED HDG. THINGS WE COULD HAVE DONE: QUERY A CTLR; EVEN THE NEW YORK GUYS MAKE MISTAKES ALTHOUGH I DO THINK THEY ARE SOME OF THE BEST IN THE BUSINESS.