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ZSE controller experienced operational error at FL330 when allowing traffic to descend via pilot's discretion resulting in a loss of separation.
| Attributes | |
| ACN | 690237 |
| Time | |
| Date | 200603 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : imb.vortac |
| State Reference | OR |
| Altitude | msl single value : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zse.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : n/s |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zse.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Series (DC-9-80) Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : n/s |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar controller : military |
| Experience | controller military : 4 controller radar : 22 controller time certified in position1 : 16 |
| ASRS Report | 690237 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | atc equipment : conflict alert other controllera |
| Resolutory Action | controller : issued new clearance controller : issued alert |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 28320 vertical : 700 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
Sequencing air carrier X and air carrier Y inbound to pdx. Both assigned speeds to achieve separation. Air carrier Y at FL340 behind and below air carrier X at FL400 same course. Issued air carrier X pilot's discretion to FL350 with speed reduction. Issued air carrier Y pilot's discretion to FL240 with speed reduction. When air carrier Y started descent; leaving FL329; I issued FL330 to air carrier X. Loss of separation occurred. Issued air carrier Y to increase rate of descent for traffic. Air carrier Y responded. Prevent recurrence: issue air carrier Y descend and maintain FL240 instead of pilot's discretion clearance.
Original NASA ASRS Text
Title: ZSE CTLR EXPERIENCED OPERROR AT FL330 WHEN ALLOWING TFC TO DSND VIA PLT'S DISCRETION RESULTING IN A LOSS OF SEPARATION.
Narrative: SEQUENCING ACR X AND ACR Y INBOUND TO PDX. BOTH ASSIGNED SPDS TO ACHIEVE SEPARATION. ACR Y AT FL340 BEHIND AND BELOW ACR X AT FL400 SAME COURSE. ISSUED ACR X PLT'S DISCRETION TO FL350 WITH SPD REDUCTION. ISSUED ACR Y PLT'S DISCRETION TO FL240 WITH SPD REDUCTION. WHEN ACR Y STARTED DSCNT; LEAVING FL329; I ISSUED FL330 TO ACR X. LOSS OF SEPARATION OCCURRED. ISSUED ACR Y TO INCREASE RATE OF DSCNT FOR TFC. ACR Y RESPONDED. PREVENT RECURRENCE: ISSUE ACR Y DSND AND MAINTAIN FL240 INSTEAD OF PLT'S DISCRETION CLRNC.
Data retrieved from NASA's ASRS site as of January 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.