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A center radar controller descended a cga CL60 aircraft to an occupied altitude resulting in loss of separation. The controller states that traffic saturation contributed to the error.
| Attributes | |
| ACN | 398345 |
| Time | |
| Date | 199804 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : lvt |
| State Reference | TN |
| Altitude | msl bound lower : 24000 msl bound upper : 24000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zid artcc : zau |
| Operator | common carrier : air carrier |
| Make Model Name | B727 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other |
| Route In Use | enroute other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : corporate |
| Make Model Name | Challenger CL600 |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Route In Use | arrival star : star |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller military : 4 controller radar : 17 |
| ASRS Report | 398345 |
| Person 2 | |
| Affiliation | government : faa |
| Function | controller : handoff position |
| Qualification | controller : radar |
| Experience | controller non radar : 3 controller radar : 10 flight time total : 350 |
| ASRS Report | 398088 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation non adherence : published procedure other anomaly other |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | controller : issued new clearance flight crew : took evasive action |
| Consequence | faa : reviewed incident with flight crew faa : investigated |
| Miss Distance | horizontal : 6000 vertical : 100 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
| Situations | |
| ATC Facility | procedure or policy : unspecified |
Narrative:
Air carrier X northbound to ord on J89 at FL240. Cga Y swbound on GUITR1 to bna at FL250. Cga Y was at FL250 due to an sdf arrival at FL240. When the sdf arrival cleared FL240, I then descended cga Y to FL240 overlooking additional traffic which was air carrier X. There were 30 data blocks at the sector. Approximately 20-25 aircraft on frequency. The sector staffing was at a maximum, non radar controller (D side), myself on radar and a handoff controller (tracker). Traffic was peaking from XP02-XP25 to bring the sector to a (red) by the flow control asd process. During this time period, frequency congestion became a major problem. Between XP09 and XP18Z there were 12 blocks resulting in having to repeat clrncs and utilizing precious time. After clearing cga Y to FL240 I observed the conflict with air carrier X approximately 6 mi apart (conflict alert had not activated yet). I issued a 270 degree heading to air carrier X and then cleared cga Y to FL200 with an expeditious descent through FL230. Air carrier X then responded to his TCASII and descended as well which resulted in a continuing loss of separation. Supplemental information from acn 398088: the sector I was working is a sequencing sector for cvg arrs. The way the airspace is flowed and arrival/departure rtes are mandated gives very little room for error. The reason aircraft X and Y got together was too many airplanes in a confined, inflexible sector. Aircraft X and aircraft Y were overlooked. My concern is that this sector's oversaturation is a daily occurrence. Supplemental information from acn 398417: TCASII TA for aircraft 800 ft above, descending approximately 2 O'clock, 10 NM. Then TCASII descend RA for aircraft 600 ft above, descending approximately 3 O'clock, 8 NM. Captain disconnected autoplt and initiated 1800 FPM descent in 1500-2000 FPM ivsi green TCASII arc. TCASII increase descent RA followed and was complied with. Copilot estimates .25 NM separation between aircraft as other aircraft descended through our altitude behind us. During this time ATC got acknowledgement by other aircraft of visual contact with our aircraft -- ATC did not advise us of other aircraft. Lowest altitude during maneuver was FL228.
Original NASA ASRS Text
Title: A CTR RADAR CTLR DSNDED A CGA CL60 ACFT TO AN OCCUPIED ALT RESULTING IN LOSS OF SEPARATION. THE CTLR STATES THAT TFC SATURATION CONTRIBUTED TO THE ERROR.
Narrative: ACR X NBOUND TO ORD ON J89 AT FL240. CGA Y SWBOUND ON GUITR1 TO BNA AT FL250. CGA Y WAS AT FL250 DUE TO AN SDF ARR AT FL240. WHEN THE SDF ARR CLRED FL240, I THEN DSNDED CGA Y TO FL240 OVERLOOKING ADDITIONAL TFC WHICH WAS ACR X. THERE WERE 30 DATA BLOCKS AT THE SECTOR. APPROX 20-25 ACFT ON FREQ. THE SECTOR STAFFING WAS AT A MAX, NON RADAR CTLR (D SIDE), MYSELF ON RADAR AND A HDOF CTLR (TRACKER). TFC WAS PEAKING FROM XP02-XP25 TO BRING THE SECTOR TO A (RED) BY THE FLOW CTL ASD PROCESS. DURING THIS TIME PERIOD, FREQ CONGESTION BECAME A MAJOR PROB. BTWN XP09 AND XP18Z THERE WERE 12 BLOCKS RESULTING IN HAVING TO REPEAT CLRNCS AND UTILIZING PRECIOUS TIME. AFTER CLRING CGA Y TO FL240 I OBSERVED THE CONFLICT WITH ACR X APPROX 6 MI APART (CONFLICT ALERT HAD NOT ACTIVATED YET). I ISSUED A 270 DEG HDG TO ACR X AND THEN CLRED CGA Y TO FL200 WITH AN EXPEDITIOUS DSCNT THROUGH FL230. ACR X THEN RESPONDED TO HIS TCASII AND DSNDED AS WELL WHICH RESULTED IN A CONTINUING LOSS OF SEPARATION. SUPPLEMENTAL INFO FROM ACN 398088: THE SECTOR I WAS WORKING IS A SEQUENCING SECTOR FOR CVG ARRS. THE WAY THE AIRSPACE IS FLOWED AND ARR/DEP RTES ARE MANDATED GIVES VERY LITTLE ROOM FOR ERROR. THE REASON ACFT X AND Y GOT TOGETHER WAS TOO MANY AIRPLANES IN A CONFINED, INFLEXIBLE SECTOR. ACFT X AND ACFT Y WERE OVERLOOKED. MY CONCERN IS THAT THIS SECTOR'S OVERSATURATION IS A DAILY OCCURRENCE. SUPPLEMENTAL INFO FROM ACN 398417: TCASII TA FOR ACFT 800 FT ABOVE, DSNDING APPROX 2 O'CLOCK, 10 NM. THEN TCASII DSND RA FOR ACFT 600 FT ABOVE, DSNDING APPROX 3 O'CLOCK, 8 NM. CAPT DISCONNECTED AUTOPLT AND INITIATED 1800 FPM DSCNT IN 1500-2000 FPM IVSI GREEN TCASII ARC. TCASII INCREASE DSCNT RA FOLLOWED AND WAS COMPLIED WITH. COPLT ESTIMATES .25 NM SEPARATION BTWN ACFT AS OTHER ACFT DSNDED THROUGH OUR ALT BEHIND US. DURING THIS TIME ATC GOT ACKNOWLEDGEMENT BY OTHER ACFT OF VISUAL CONTACT WITH OUR ACFT -- ATC DID NOT ADVISE US OF OTHER ACFT. LOWEST ALT DURING MANEUVER WAS FL228.
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.