MD80 CREW HAD TCASII TA WITH A FORMATION OF SIX JUMP ACFT ON THE BRADFORD 3 STAR INTO ORD.

Narrative

TFC ALERT FROM TCASII. DURING DESCENT ON THE BFD STAR TO ORD AT ABOUT 14000 FT AND DURING INTERMITTENT IMC WE RECEIVED A TA FROM THE TCASII PAINTING A TARGET MINUS 200 FT AND LESS THAN 2 MI. WE HAD DEVIATED FROM THE ARRIVAL TO THE NORTH BY APROX 2 NM AND THE TARGET WAS AT OUR 3 OCLOCK POSITION WHICH PUT IT PRETTY MUCH ON TOP OF THE STARS ARRIVAL COURSE. UPON BREAKING OUT FROM IMC WE VISUALLY ACQUIRED THE TARGET AND DISCOVERED TO OUR DISMAY THAT THEIR WAS NOT ONE ACFT BUT SIX AND THESE ACFT WERE IN MARGINAL VMC. WE IMMEDIATELY ADVISED CHICAGO ARTCC AND THEIR RESPONSE WAS THAT THERE WERE ACFT AND PARACHUTE JUMPERS IN THE AREA. OUR CONCERN WAS THIS: HAD WE BEEN ON COURSE AND RECEIVED AN RA IMMEDIATELY AFTER LEAVING IMC A MID AIR COLLISION WAS PROBABLE BECAUSE ONLY ONE OF THE TARGETS WAS ON THE TCASII. THE ACFT WERE IN A LOOSE FORMATION AND RESPONDING TO A RA WOULD LIKELY HAVE PUT US INTO THE PATH OF ANOTHER ACFT IN THE FORMATION. I HAVE NOTHING AGAINST GA BUT WHY DO PARACHUTE JUMPERS HAVE TO PLY THEIR TRADE ON TOP OF A STAR TO THE BUSIEST ARPT IN THE WORLD.