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Air carrier X descent through occupied altitude had less than standard separation from mlt. Evasive action taken. System error.
| Attributes | |
| ACN | 253762 |
| Time | |
| Date | 199310 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : huo |
| State Reference | NY |
| Altitude | msl bound lower : 8000 msl bound upper : 8000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Transport, High Wing, 2 Turboprop Eng |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | enroute : on vectors enroute airway : zbw |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | other |
| Make Model Name | Military Transport |
| 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 non radar : 2 controller radar : 2 |
| ASRS Report | 253762 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 480 flight time total : 5500 flight time type : 3500 |
| ASRS Report | 253923 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : published procedure non adherence : required legal separation |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | controller : issued new clearance flight crew : took evasive action |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 18000 vertical : 400 |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
During a busy session with 20 mi in trail required to ewr the error occurred. I amended air carrier X altitude and thought he had acknowledged the clearance, when he had really said, 'basically blocked.' air carrier X descended to his original altitude and conflicted with mlt. Volume, lack of flow control, and lack of clarity on the frequencys all were factors, I felt. Perhaps if workload had been lessened by better flow control, or the frequencys had been clearer, or if I had had another set of ears listening, the error might not have occurred. Supplemental information from acn 253923: air carrier X left a cruising altitude of 11000 ft down to 7000 ft as assigned. I noticed a military aircraft and turned right to avoid converging flight paths. I slowed descent and at around 8000 ft, the controller told us to climb back to 9000 ft. Supplemental information from acn 254188: air carrier X en route from ith to ewr was given descent clearance to 7000 from 11000. Mlt type approached our course from right. When we realized we were converging, we turned right to avoid. Controller instructed us to climb to 9000 ft simultaneously. When we heard controller's instruction we climbed to 9000 as directed.
Original NASA ASRS Text
Title: ACR X DSCNT THROUGH OCCUPIED ALT HAD LTSS FROM MLT. EVASIVE ACTION TAKEN. SYS ERROR.
Narrative: DURING A BUSY SESSION WITH 20 MI IN TRAIL REQUIRED TO EWR THE ERROR OCCURRED. I AMENDED ACR X ALT AND THOUGHT HE HAD ACKNOWLEDGED THE CLRNC, WHEN HE HAD REALLY SAID, 'BASICALLY BLOCKED.' ACR X DSNDED TO HIS ORIGINAL ALT AND CONFLICTED WITH MLT. VOLUME, LACK OF FLOW CTL, AND LACK OF CLARITY ON THE FREQS ALL WERE FACTORS, I FELT. PERHAPS IF WORKLOAD HAD BEEN LESSENED BY BETTER FLOW CTL, OR THE FREQS HAD BEEN CLEARER, OR IF I HAD HAD ANOTHER SET OF EARS LISTENING, THE ERROR MIGHT NOT HAVE OCCURRED. SUPPLEMENTAL INFO FROM ACN 253923: ACR X LEFT A CRUISING ALT OF 11000 FT DOWN TO 7000 FT AS ASSIGNED. I NOTICED A MIL ACFT AND TURNED R TO AVOID CONVERGING FLT PATHS. I SLOWED DSCNT AND AT AROUND 8000 FT, THE CTLR TOLD US TO CLB BACK TO 9000 FT. SUPPLEMENTAL INFO FROM ACN 254188: ACR X ENRTE FROM ITH TO EWR WAS GIVEN DSCNT CLRNC TO 7000 FROM 11000. MLT TYPE APCHED OUR COURSE FROM R. WHEN WE REALIZED WE WERE CONVERGING, WE TURNED R TO AVOID. CTLR INSTRUCTED US TO CLB TO 9000 FT SIMULTANEOUSLY. WHEN WE HEARD CTLR'S INSTRUCTION WE CLBED TO 9000 AS DIRECTED.
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.