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ZFW controller described TCAS RA event when air carrier level at FL250 responded to a TCAS alert; descent to FL240; reporter citing only traffic at FL210 with inoperative mode C equipment.
| Attributes | |
| ACN | 813815 |
| Time | |
| Date | 200811 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : zfw.airport |
| State Reference | TX |
| Altitude | msl single value : 25000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zfw.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport Low Wing 2 Turbojet Eng |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zfw.artcc |
| Operator | other |
| Make Model Name | Military Transport |
| Operating Under FAR Part | Part 91 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : military controller : radar controller : non radar |
| Experience | controller limited radar : 2 controller military : 5 controller non radar : 4 controller radar : 9 controller supervisory : 5 controller time certified in position1 : 3 |
| ASRS Report | 813815 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe |
| Independent Detector | aircraft equipment : tcas other controllera |
| Resolutory Action | controller : issued new clearance flight crew : took evasive action |
| Miss Distance | horizontal : 3000 vertical : 0 |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
The aircraft X was in level flight at FL250 when the pilot reported responding to a TCAS RA and began a descent. I observed no other traffic within the vicinity of the MD80 except for an aircraft Y with mode C inoperative level at FL210 on a converging course. I advised the MD80 of this traffic and the pilot of the aircraft X chose to level at FL240; which I responded and told him to maintain. I believe TCAS could have caused a collision in this situation had I not been there to advise the aircraft X pilot of the converging aircraft Y. Again; there was no other traffic near the aircraft X to cause a TCAS RA.
Original NASA ASRS Text
Title: ZFW CONTROLLER DESCRIBED TCAS RA EVENT WHEN AIR CARRIER LEVEL AT FL250 RESPONDED TO A TCAS ALERT; DESCENT TO FL240; REPORTER CITING ONLY TRAFFIC AT FL210 WITH INOPERATIVE MODE C EQUIPMENT.
Narrative: THE ACFT X WAS IN LEVEL FLT AT FL250 WHEN THE PLT RPTED RESPONDING TO A TCAS RA AND BEGAN A DSCNT. I OBSERVED NO OTHER TFC WITHIN THE VICINITY OF THE MD80 EXCEPT FOR AN ACFT Y WITH MODE C INOP LEVEL AT FL210 ON A CONVERGING COURSE. I ADVISED THE MD80 OF THIS TFC AND THE PLT OF THE ACFT X CHOSE TO LEVEL AT FL240; WHICH I RESPONDED AND TOLD HIM TO MAINTAIN. I BELIEVE TCAS COULD HAVE CAUSED A COLLISION IN THIS SITUATION HAD I NOT BEEN THERE TO ADVISE THE ACFT X PLT OF THE CONVERGING ACFT Y. AGAIN; THERE WAS NO OTHER TFC NEAR THE ACFT X TO CAUSE A TCAS RA.
Data retrieved from NASA's ASRS site as of May 2009 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.