 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
Small transport Y descent to occupied altitude had less than standard separation from atx X. System error.
| Attributes | |
| ACN | 232171 |
| Time | |
| Date | 199301 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : vis |
| State Reference | CA |
| Altitude | msl bound lower : 14000 msl bound upper : 14000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air taxi |
| Make Model Name | Small Transport, Low Wing, 2 Turboprop Eng |
| Flight Phase | descent other |
| Route In Use | enroute : direct enroute airway : zoa |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | general aviation : personal |
| Make Model Name | Small Transport, Low Wing, 2 Turboprop Eng |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller military : 2 controller non radar : 2 controller radar : 15 |
| ASRS Report | 232171 |
| Person 2 | |
| Affiliation | company : air taxi |
| 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 | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 6000 vertical : 500 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Atx X was inbound from the south on altta arrival to fat at 14000 ft. Small transport Y was on the same route at 15000 ft and 1 mi in trail with a slight overtake. A flight of 2 fgts were also on a recovery to fat from over nlc. The fgt's flight was vectored eastbound, descended and split into 2 single aircraft. Atx X was issued a descent clearance (no reply) and slowed to follow the fgts. The fgts were sequenced in front of both atx X and small transport Y. The altitude readout on atx X was lost (intermittent) for a period of over 35 seconds. The 'data' blocks of the 4 aircraft were close, and the controller thought he observed an altitude of 12700 ft in atx X data block. At this time small transport Y was slightly ahead of atx X. Small transport Y was descended to FL140. Conflict alert activated shortly afterwards and showed atx X at 13900 ft and small transport Y at 14400 ft. Again atx X was told to descend to 11000 ft but not in time to prevent loss of separation. 2 mins prior to error, sector was split (d-side added). This and numerous UHF aircraft on frequency added to distraction on part of controller to monitor mode C on atx X.
Original NASA ASRS Text
Title: SMT Y DSCNT TO OCCUPIED ALT HAD LTSS FROM ATX X. SYS ERROR.
Narrative: ATX X WAS INBOUND FROM THE S ON ALTTA ARR TO FAT AT 14000 FT. SMT Y WAS ON THE SAME RTE AT 15000 FT AND 1 MI IN TRAIL WITH A SLIGHT OVERTAKE. A FLT OF 2 FGTS WERE ALSO ON A RECOVERY TO FAT FROM OVER NLC. THE FGT'S FLT WAS VECTORED EBOUND, DSNDED AND SPLIT INTO 2 SINGLE ACFT. ATX X WAS ISSUED A DSCNT CLRNC (NO REPLY) AND SLOWED TO FOLLOW THE FGTS. THE FGTS WERE SEQUENCED IN FRONT OF BOTH ATX X AND SMT Y. THE ALT READOUT ON ATX X WAS LOST (INTERMITTENT) FOR A PERIOD OF OVER 35 SECONDS. THE 'DATA' BLOCKS OF THE 4 ACFT WERE CLOSE, AND THE CTLR THOUGHT HE OBSERVED AN ALT OF 12700 FT IN ATX X DATA BLOCK. AT THIS TIME SMT Y WAS SLIGHTLY AHEAD OF ATX X. SMT Y WAS DSNDED TO FL140. CONFLICT ALERT ACTIVATED SHORTLY AFTERWARDS AND SHOWED ATX X AT 13900 FT AND SMT Y AT 14400 FT. AGAIN ATX X WAS TOLD TO DSND TO 11000 FT BUT NOT IN TIME TO PREVENT LOSS OF SEPARATION. 2 MINS PRIOR TO ERROR, SECTOR WAS SPLIT (D-SIDE ADDED). THIS AND NUMEROUS UHF ACFT ON FREQ ADDED TO DISTR ON PART OF CTLR TO MONITOR MODE C ON ATX X.
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.