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Air carrier Y descent to occupied altitude had less than standard separation from air carrier X. System error.
| Attributes | |
| ACN | 216121 |
| Time | |
| Date | 199207 |
| Day | Thu |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : ord |
| State Reference | IL |
| Altitude | msl bound lower : 4000 msl bound upper : 4000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : ord artcc : zla |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | enroute : on vectors |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| ASRS Report | 216121 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : published procedure non adherence : required legal separation |
| Independent Detector | other other : unspecified atc |
| Resolutory Action | controller : issued new clearance other |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 12000 vertical : 0 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
I was working runway 27R arrs on simultaneous ILS approachs. It was the beginning of a rush and the operation was very complex due to high volume, a strong northeast tailwind, and numerous similar call signs. Air carrier X was at 4000 on right base for runway 27R at 190 KTS. Air carrier Y was on a 180 degree heading to fall in behind air carrier Y at 190 KTS and 7000. Air carrier Y was then assigned 4000 and turned to 110 degrees to follow air carrier X. Air carrier X was then turned south to maintain divergence with air carrier Y. The supervisor then asked if I had the 2 aircraft ok. I felt I was applying appropriate separation but descended air carrier X to 3000 anyway. I believe the situation occurred because the 110 heading issued to air carrier Y should have been 090 so as not to cut off air carrier X. I could have been more aware of issued headings and perhaps we shouldn't be landing downwind.
Original NASA ASRS Text
Title: ACR Y DSCNT TO OCCUPIED ALT HAD LTSS FROM ACR X. SYS ERROR.
Narrative: I WAS WORKING RWY 27R ARRS ON SIMULTANEOUS ILS APCHS. IT WAS THE BEGINNING OF A RUSH AND THE OP WAS VERY COMPLEX DUE TO HIGH VOLUME, A STRONG NE TAILWIND, AND NUMEROUS SIMILAR CALL SIGNS. ACR X WAS AT 4000 ON R BASE FOR RWY 27R AT 190 KTS. ACR Y WAS ON A 180 DEG HDG TO FALL IN BEHIND ACR Y AT 190 KTS AND 7000. ACR Y WAS THEN ASSIGNED 4000 AND TURNED TO 110 DEGS TO FOLLOW ACR X. ACR X WAS THEN TURNED S TO MAINTAIN DIVERGENCE WITH ACR Y. THE SUPVR THEN ASKED IF I HAD THE 2 ACFT OK. I FELT I WAS APPLYING APPROPRIATE SEPARATION BUT DSNDED ACR X TO 3000 ANYWAY. I BELIEVE THE SITUATION OCCURRED BECAUSE THE 110 HDG ISSUED TO ACR Y SHOULD HAVE BEEN 090 SO AS NOT TO CUT OFF ACR X. I COULD HAVE BEEN MORE AWARE OF ISSUED HDGS AND PERHAPS WE SHOULDN'T BE LNDG DOWNWIND.
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.