Narrative:

Flight was a scheduled B747 freighter service by a large international carrier (foreign registered). ATC instructions were to intercept ILS runway 27L at 5000 ft, maintain 5000 ft till 'wavie,' cleared ILS runway 27L, speed 170 KIAS till 'wiltt' (LOM). Captain (PF) was on course, slightly left of centerline. TCASII was still in 'TA/RA' mode. 1 mi from 'wavie' (where GS intercept should occur). TCASII TA sounded. Other aircraft approaching from the north, turning to intercept runway 27R centerline. Aircraft symbol on TCASII displayed -400 ft (4600 ft MSL). Shortly after TA, we received an RA. TCASII commanded 'climb' with approximately a +1500 FPM command. Captain followed TCASII command, and I alerted ATC of 'TCASII climb.' I acquired the other aircraft visually, a major united states carrier, a DC10 airplane. Other aircraft appeared to overshoot the runway 27R localizer beam. I observed it in a right turn, about 1200-2000 ft to our right and 400 ft below. ATC advised us that he was on final runway 27R. Had we been in 'TA' only, as many pubs recommend for closely- spaced parallel approachs, the 'RA' would not have sounded. Potential for collision would have been much higher, as GS intercept occurred as 'RA' sounded. Descent on GS would have reduced vertical separation. Other aircraft did not appear to descend so I suspect the crew had already selected 'TA only.' human factors: it is very difficult to pick out traffic that is below your altitude, at night, over a brightly-lit city. Thorough visual scan is required -- do not allow scan to become lax in TCASII equipped aircraft. ATC: recommend 'staggered' position on parallel approachs. Example: aircraft on left side 1-2 NM ahead of aircraft on right side. Most approachs are flown at a common (ATC-directed) airspeed, so 'staggering' would be maintained. Procedures: recommend TA/RA until FAF/LOM, very little maneuvering will occur inside that point. Equipment: put TCASII in all large aircraft operated under far 121, including freighters. I am now a big supporter of TCASII.

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Original NASA ASRS Text

Title: SIMULTANEOUS ILS APCHS WERE IN PROGRESS AT ORD ON THE RWY 27'S. DC10 OVERSHOT ILS RWY 27R LOC AND SET OFF THE TCASII RA ON A B747 ON LOC RWY 27L. B747 TCASII IN RA MODE, ISSUES CLB COMMAND. RPTR CONCERNED OVER FACT THAT TCASII OPS ORDER SAYS TO USE TA IN THESE TYPE APCHS. IF FOLLOWED, THE TFC SEPARATION WOULD HAVE DECREASED.

Narrative: FLT WAS A SCHEDULED B747 FREIGHTER SVC BY A LARGE INTL CARRIER (FOREIGN REGISTERED). ATC INSTRUCTIONS WERE TO INTERCEPT ILS RWY 27L AT 5000 FT, MAINTAIN 5000 FT TILL 'WAVIE,' CLRED ILS RWY 27L, SPD 170 KIAS TILL 'WILTT' (LOM). CAPT (PF) WAS ON COURSE, SLIGHTLY L OF CTRLINE. TCASII WAS STILL IN 'TA/RA' MODE. 1 MI FROM 'WAVIE' (WHERE GS INTERCEPT SHOULD OCCUR). TCASII TA SOUNDED. OTHER ACFT APCHING FROM THE N, TURNING TO INTERCEPT RWY 27R CTRLINE. ACFT SYMBOL ON TCASII DISPLAYED -400 FT (4600 FT MSL). SHORTLY AFTER TA, WE RECEIVED AN RA. TCASII COMMANDED 'CLB' WITH APPROX A +1500 FPM COMMAND. CAPT FOLLOWED TCASII COMMAND, AND I ALERTED ATC OF 'TCASII CLB.' I ACQUIRED THE OTHER ACFT VISUALLY, A MAJOR UNITED STATES CARRIER, A DC10 AIRPLANE. OTHER ACFT APPEARED TO OVERSHOOT THE RWY 27R LOC BEAM. I OBSERVED IT IN A R TURN, ABOUT 1200-2000 FT TO OUR R AND 400 FT BELOW. ATC ADVISED US THAT HE WAS ON FINAL RWY 27R. HAD WE BEEN IN 'TA' ONLY, AS MANY PUBS RECOMMEND FOR CLOSELY- SPACED PARALLEL APCHS, THE 'RA' WOULD NOT HAVE SOUNDED. POTENTIAL FOR COLLISION WOULD HAVE BEEN MUCH HIGHER, AS GS INTERCEPT OCCURRED AS 'RA' SOUNDED. DSCNT ON GS WOULD HAVE REDUCED VERT SEPARATION. OTHER ACFT DID NOT APPEAR TO DSND SO I SUSPECT THE CREW HAD ALREADY SELECTED 'TA ONLY.' HUMAN FACTORS: IT IS VERY DIFFICULT TO PICK OUT TFC THAT IS BELOW YOUR ALT, AT NIGHT, OVER A BRIGHTLY-LIT CITY. THOROUGH VISUAL SCAN IS REQUIRED -- DO NOT ALLOW SCAN TO BECOME LAX IN TCASII EQUIPPED ACFT. ATC: RECOMMEND 'STAGGERED' POS ON PARALLEL APCHS. EXAMPLE: ACFT ON L SIDE 1-2 NM AHEAD OF ACFT ON R SIDE. MOST APCHS ARE FLOWN AT A COMMON (ATC-DIRECTED) AIRSPD, SO 'STAGGERING' WOULD BE MAINTAINED. PROCS: RECOMMEND TA/RA UNTIL FAF/LOM, VERY LITTLE MANEUVERING WILL OCCUR INSIDE THAT POINT. EQUIP: PUT TCASII IN ALL LARGE ACFT OPERATED UNDER FAR 121, INCLUDING FREIGHTERS. I AM NOW A BIG SUPPORTER OF TCASII.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.