NMAC BTWN A B727 CLBING OUT AFTER TKOF AND A BEECHCRAFT BE200 ON A CONVERGING COURSE. THE B727 TOOK EVASIVE ACTION BY CLBING IN RESPONSE TO TCASII RA AND VISUAL SIGHTING OF THE OTHER ACFT.

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WE DEPARTED ORD RWY 22L. INITIAL CLRED ALT WAS 5000 FT AND ASSIGNED HDG 110 DEGS. WE SWITCHED TO DEP AND WERE GIVEN HDG 040 DEGS AND CLB TO 13000 FT; 'TIGHTEN YOUR TURN UP AS MUCH AS POSSIBLE.' WHILE TURNING THROUGH 100 DEGS; I ACQUIRED AN AIRPLANE SLIGHTLY HIGHER THAN OUR CURRENT ALT AND ON WHAT APPEARED TO BE A CONVERGING HDG. THE FO WAS THE PF. I COMMUNICATED THE TFC TO THE CREW. IN MY MIND; I FIGURED THAT THE TFC IN QUESTION MUST BE FURTHER AWAY THAN IT APPEARED OR THAT ORD WOULD DSND IT SOON. WHEN ITS RELATIVE POS STAYED FIXED IN MY #2 WINDOW FOR A FEW MORE SECONDS; I BEGAN TO DOUBT OUR CONTINUED SEPARATION. I MAY HAVE GIVEN THE FO SOME GUIDANCE COMMANDS. THEN THE TCASII ANNOUNCED 'TFC.' THEN I BELIEVE WE GOT A 'CLB' RA; THEN A 'MONITOR VERT SPD' RA THEN A 'DSND' RA. (NOTE: MY RECOLLECTION OF THE RA'S AND THEIR SEQUENCE MAY BE FLAWED AS 95 PERCENT OF MY ATTN WAS OUTSIDE THE AIRPLANE AND CONCENTRATED ON THE TFC.) WHEN THE 'DSND' OR 'DSND NOW' RA WAS GIVEN AND THE FO BEGAN TO FOLLOW THE TCASII IVSI COMMAND FOR THE DSCNT; I FELT THAT THE AIRPLANE WAS IN JEOPARDY OF A COLLISION. I TOOK CTL OF THE AIRPLANE AND FIREWALLED THE THRUST LEVERS; AND SMARTLY PITCHED THE NOSE UP. THE ACFT WAS INDUCED INTO AN ACCELERATED PRESTALL BUFFET AND POSSIBLY A TAIL STALL. IN MY ESTIMATION THE ACFT IN QUESTION PASSED UNDER US WITHIN 500 FT. THE ENGS RAN AT FIREWALL THRUST FOR LESS THAN 30 SECONDS AND THE BUFFETING LASTED LESS THAN 10 SECONDS. AREA MGR OF ORD APCH WAS CONTACTED AND SAID THE INCIDENT WAS UNDER INVESTIGATION AND THAT THEY WERE REVIEWING THE TAPES. I TOLD HER ON A SECOND CALL THAT I WOULD BE FILING THIS NMAC RPT AFTER CONSULTING OUR DIRECTOR OF FLT SAFETY. THE ABOVE ENG AND AIRFRAME OBSERVATIONS WERE WRITTEN IN THE AIRPLANE LOGBOOK. WE WERE CLBING NEAR VZF AND THE SPD AT WHICH I PERFORMED THE ABRUPT MANEUVER WAS UNDER 250 KTS. WE HAD A CAPT JUMPSEATER IN THE FIRST OBSERVER SEAT. THE OTHER AIRPLANE WAS A BEECH 200.