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Air carrier responds to TCASII RA and descend into air carrier traffic opposite direction. Air carrier climbed back up before loss of separation occurred.
| Attributes | |
| ACN | 206133 |
| Time | |
| Date | 199203 |
| Day | Fri |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : shv |
| State Reference | LA |
| Altitude | msl bound lower : 26000 msl bound upper : 28000 |
| Environment | |
| Flight Conditions | Marginal |
| Light | Dusk |
| Aircraft 1 | |
| Controlling Facilities | artcc : zfw artcc : zkc |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : corporate |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller military : 6 controller non radar : 6 controller radar : 12 controller supervisory : 2 |
| ASRS Report | 206133 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 16600 flight time type : 7000 |
| ASRS Report | 205811 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Miss Distance | horizontal : 36000 vertical : 700 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Air carrier X at FL270 received a TCASII RA to descend because traffic (cga Y at FL280) was supposedly in conflict. Aircraft were separated by required 1000 vertical separation. Air carrier X executed a descent which immediately put him in conflict with air carrier Z, who was head-on at FL260. Merging target traffic was not issued to either aircraft due to workload at the time. Crew of air carrier X reported a 'TCASII RA' and executed a descent to 26700 before climbing back to FL270. Crew also reported that air carrier Z (FL260) was eventually idented by TCASII. It is the opinion of this controller that this RA could have created a possible midair collision. This incident or similar incidents have occurred before at ft worth ARTCC. It appears TCASII does not identify more than 1 conflict at a time, and the answer is always climb or descend which are usually the last option used by a controller. A turn will usually suffice vs up or down. Air carrier X and air carrier Z were approximately 10 mi apart head on! Supplemental information from acn 205811: received traffic alert on TCASII system display showed 1/2 yellow ball at 12 O'clock position on edge of TCASII display altitude data of intruder was not visible. Intruder symbol moved from 12 O'clock to 10 O'clock on edge of display at which point it then moved directly in toward subject aircraft symbol of display unmasking altitude data which indicated plus 8 (plus 800 ft) and at that instant, a RA 'descend now' sounded at a descent rate of 1800 FPM and appeared on the visual display. Descent was begun at that time and aircraft had descended 200 ft when 'monitor descent' and was sounded. Aircraft leveled out at 26700 ft and started climb back to 27000 ft. Simultaneously as we leveled and started a climb, we were finally able to advise ATC of our deviation (the frequency was quite busy at that time) and that we were returning to our assigned altitude. The controller advised us that we had additional traffic at 12 O'clock at FL260 and as he was transmitting, we received a second traffic alert with an intruder symbol at 12 O'clock and altitude data indicating -7.
Original NASA ASRS Text
Title: ACR RESPONDS TO TCASII RA AND DSND INTO ACR TFC OPPOSITE DIRECTION. ACR CLBED BACK UP BEFORE LOSS OF SEPARATION OCCURRED.
Narrative: ACR X AT FL270 RECEIVED A TCASII RA TO DSND BECAUSE TFC (CGA Y AT FL280) WAS SUPPOSEDLY IN CONFLICT. ACFT WERE SEPARATED BY REQUIRED 1000 VERT SEPARATION. ACR X EXECUTED A DSCNT WHICH IMMEDIATELY PUT HIM IN CONFLICT WITH ACR Z, WHO WAS HEAD-ON AT FL260. MERGING TARGET TFC WAS NOT ISSUED TO EITHER ACFT DUE TO WORKLOAD AT THE TIME. CREW OF ACR X RPTED A 'TCASII RA' AND EXECUTED A DSCNT TO 26700 BEFORE CLBING BACK TO FL270. CREW ALSO RPTED THAT ACR Z (FL260) WAS EVENTUALLY IDENTED BY TCASII. IT IS THE OPINION OF THIS CTLR THAT THIS RA COULD HAVE CREATED A POSSIBLE MIDAIR COLLISION. THIS INCIDENT OR SIMILAR INCIDENTS HAVE OCCURRED BEFORE AT FT WORTH ARTCC. IT APPEARS TCASII DOES NOT IDENT MORE THAN 1 CONFLICT AT A TIME, AND THE ANSWER IS ALWAYS CLB OR DSND WHICH ARE USUALLY THE LAST OPTION USED BY A CTLR. A TURN WILL USUALLY SUFFICE VS UP OR DOWN. ACR X AND ACR Z WERE APPROX 10 MI APART HEAD ON! SUPPLEMENTAL INFO FROM ACN 205811: RECEIVED TFC ALERT ON TCASII SYS DISPLAY SHOWED 1/2 YELLOW BALL AT 12 O'CLOCK POS ON EDGE OF TCASII DISPLAY ALT DATA OF INTRUDER WAS NOT VISIBLE. INTRUDER SYMBOL MOVED FROM 12 O'CLOCK TO 10 O'CLOCK ON EDGE OF DISPLAY AT WHICH POINT IT THEN MOVED DIRECTLY IN TOWARD SUBJECT ACFT SYMBOL OF DISPLAY UNMASKING ALT DATA WHICH INDICATED PLUS 8 (PLUS 800 FT) AND AT THAT INSTANT, A RA 'DSND NOW' SOUNDED AT A DSCNT RATE OF 1800 FPM AND APPEARED ON THE VISUAL DISPLAY. DSCNT WAS BEGUN AT THAT TIME AND ACFT HAD DSNDED 200 FT WHEN 'MONITOR DSCNT' AND WAS SOUNDED. ACFT LEVELED OUT AT 26700 FT AND STARTED CLB BACK TO 27000 FT. SIMULTANEOUSLY AS WE LEVELED AND STARTED A CLB, WE WERE FINALLY ABLE TO ADVISE ATC OF OUR DEV (THE FREQ WAS QUITE BUSY AT THAT TIME) AND THAT WE WERE RETURNING TO OUR ASSIGNED ALT. THE CTLR ADVISED US THAT WE HAD ADDITIONAL TFC AT 12 O'CLOCK AT FL260 AND AS HE WAS XMITTING, WE RECEIVED A SECOND TFC ALERT WITH AN INTRUDER SYMBOL AT 12 O'CLOCK AND ALT DATA INDICATING -7.
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.