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Air carrier receives TCASII RA on air carrier descending from above and descends into air carrier below. Controller intervened.
| Attributes | |
| ACN | 221358 |
| Time | |
| Date | 199209 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : ord |
| State Reference | IL |
| Altitude | msl bound lower : 23000 msl bound upper : 24000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zau |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | descent other |
| Route In Use | enroute airway : zau |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 13400 flight time type : 3000 |
| ASRS Report | 221358 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 20000 flight time type : 4000 |
| ASRS Report | 221596 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : required legal separation other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa |
| Resolutory Action | controller : issued new clearance |
| Consequence | Other |
| Miss Distance | horizontal : 16800 vertical : 0 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were on a radar vector and I was flying as first officer on flight (air carrier X) from slc to ord. We were on arrival to ord currently level at FL240. Our TCASII system gave a RA because of traffic descending above us (air carrier Y). I informed ZAU that we were descending out of FL240 because of a TCASII warning. As we were approaching FL230, center told us to climb to FL240. (Air carrier Y had leveled off at FL250 and air carrier Z was at FL230 in level flight). Air carrier Z told ZAU that we had come close to them, and the center told them we descended because of a TCASII warning. In my opinion, it would have been better if we had not followed the directions from TCASII. I believe TCASII should be simplified in interpretation and more flexible in its directions (e.g., turns left or right might be more desirable than a 'fly to' indication of 3000 FPM descent). Because of its limitations, I think TCASII should be more advisory and less directive in its use. Supplemental information from acn 221288: an erroneous TCASII resolution put 2 aircraft in immediate danger.
Original NASA ASRS Text
Title: ACR RECEIVES TCASII RA ON ACR DSNDING FROM ABOVE AND DSNDS INTO ACR BELOW. CTLR INTERVENED.
Narrative: WE WERE ON A RADAR VECTOR AND I WAS FLYING AS FO ON FLT (ACR X) FROM SLC TO ORD. WE WERE ON ARR TO ORD CURRENTLY LEVEL AT FL240. OUR TCASII SYS GAVE A RA BECAUSE OF TFC DSNDING ABOVE US (ACR Y). I INFORMED ZAU THAT WE WERE DSNDING OUT OF FL240 BECAUSE OF A TCASII WARNING. AS WE WERE APCHING FL230, CTR TOLD US TO CLB TO FL240. (ACR Y HAD LEVELED OFF AT FL250 AND ACR Z WAS AT FL230 IN LEVEL FLT). ACR Z TOLD ZAU THAT WE HAD COME CLOSE TO THEM, AND THE CTR TOLD THEM WE DSNDED BECAUSE OF A TCASII WARNING. IN MY OPINION, IT WOULD HAVE BEEN BETTER IF WE HAD NOT FOLLOWED THE DIRECTIONS FROM TCASII. I BELIEVE TCASII SHOULD BE SIMPLIFIED IN INTERPRETATION AND MORE FLEXIBLE IN ITS DIRECTIONS (E.G., TURNS L OR R MIGHT BE MORE DESIRABLE THAN A 'FLY TO' INDICATION OF 3000 FPM DSCNT). BECAUSE OF ITS LIMITATIONS, I THINK TCASII SHOULD BE MORE ADVISORY AND LESS DIRECTIVE IN ITS USE. SUPPLEMENTAL INFO FROM ACN 221288: AN ERRONEOUS TCASII RESOLUTION PUT 2 ACFT IN IMMEDIATE DANGER.
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.