CORP TURBOJET CREW ON APCH TO MDW ACCEPTED A GARBLED XMISSION AS A LNDG CLRNC FOR RWY 31C.

Narrative

WE WERE CLRED FOR THE ILS TO 31C. THE WHOLE STAR WE WERE TOLD; TO KEEP BEST FWD SPEED. ONCE CLRED FOR THE APCH WE WERE GIVEN 170 KIAS TO RUNTS. CALL THE TWR THERE. THE FO HAD A HARD TIME GETTING THE CALL DUE TO FREQ CONGESTION. WE HEARD CLR TO LAND AND THE FO SAID; 'DID HE SAY SOMETHING ABOUT THE RIGHT SIDE?' I TOLD HIM I THINK HE WAS CALLING OUT TFC THAT WAS LNDG ON 31R. WE COMPLETED THE LNDG CHKLIST AND BOTH OBSERVED AIRPLANE LIGHTS XING RWY 31C DOWNFIELD; UPON REACHING THE DH I CALLED OUT AIRPLANE ON THE RWY 'GOING AROUND' THE FO SAW IT TOO. WE TOLD TWR WE WERE GOING AROUND HE GAVE US HEADING AND ALTITUDE AND DEP FREQ. NO ONE ACTED LIKE ANYTHING WAS WRONG. AFTER LNDG I CALLED THE TWR CAB AND ASKED SUPVR WHAT HAPPENED. HE REMARKED WHAT DO YOU MEAN? I TOLD HIM WE ALMOST LANDED ON A 737. HE TOLD ME THAT PLANE WAS CLRED POSITION AND HOLD ON 31C AND WE WERE CLRED TO LAND 31R. HE THEN SAID TELL ME YOU DIDN'T PENETRATE THE VERTICAL PLANE OF RWY. I REPLIED; NO WE DIDN'T. HE SAID GOOD HEADS UP; THANKS FOR CALLING. AFTER REVIEWING THE SIT WITH THE FO; ALL WE BELIEVE THE CTLR ISSUED WAS CLRED TO LAND ON THE RIGHT ONE OR SOMETHING CLOSE TO THIS. BUT NOT SIDE STEP TO THE RIGHT ONE OR CAN YOU TAKE THE RIGHT ONE. AS WE WENT AROUND THE CTLR WAS SNAPPING AT THE 737 TO EITHER BEGIN HIS TKOF OR CLR THE RWY. I ALSO NOTICED HE HAD ONLY HIS ANTI-COLLISION BEACONS ILLUMINATED; NO STROBES; NO LNDG OR TAXI LIGHTS AND HE WAS HOLDING ON THE DISPLACED THRESHOLD; WHICH WAS VERY DARK. THE FO AND MYSELF AGREED TO VERIFY; VERIFY; VERIFY IN THE FUTURE AND WE WERE NOT WEARING HEADSETS AT THE TIME WHICH WE BOTH BELIEVE MADE IT MORE DIFFICULT TO HEAR ATC. SUPPLEMENTAL INFO FROM ACN 530670: WHILE HOLDING SHORT OF RWY 31C SEVERAL ACFT WERE OBSERVED TO BE ON APCH TO 31C. ONE OF THESE ACFT WAS INSTRUCTED TO CHANGE THEIR APCH TO 31R AND CLRED TO LAND ON 31R. SHORTLY THEREAFTER WE WERE CLRED TO POSITION AND HOLD ON RWY 31C. LNDG LIGHTS WERE TURNED ON WHILE IN POSITION. SIMULTANEOUSLY WITH BEING CLRED FOR TKOF I HEARD A LOW FLYING ACFT AT HIGH POWER AND LOOKED UP TO OBSERVE A SMALL JET AT AN ESTIMATED ALTITUDE OF 50-100 FT EXECUTING A GAR DIRECTLY ABOVE OUR ACFT. I BELIEVE THE OTHER ACFT WAS CLRED TO LAND ON 31R AND MISTAKENLY ATTEMPTED TO LAND ON RWY 31C. HAD THE ALTERNATING LANDING LIGHT SYSTEM BEEN OPERATIONAL AND USED WHILE IN POSITION; I BELIEVE IT WOULD HAVE HELPED THE OTHER PLT RECOGNIZE THAT THERE WAS AN ACFT ON THE RWY MUCH EARLIER. SUPPLEMENTAL INFO FROM ACN 530672: I DON'T BELIEVE MDW TWR REALIZED WHAT HAPPENED BY THE CORPORATE JET EXECUTING A GAR TO THE WRONG RWY. THIS WAS A VERY CLOSE CALL AT MDW.