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Reporters write about loss of separation due to improper use of vacated altitude separation rule; leading to a loss of separation.
| Attributes | |
| ACN | 1172034 |
| Time | |
| Date | 201405 |
| Local Time Of Day | 0001-0600 |
| Place | |
| Locale Reference | ZLA.ARTCC |
| State Reference | CA |
| Environment | |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Person 1 | |
| Function | Instructor Enroute |
| Qualification | Air Traffic Control Fully Certified |
| Experience | Air Traffic Control Time Certified In Pos 1 (yrs) 12 |
| Person 2 | |
| Function | Enroute Trainee |
| Qualification | Air Traffic Control Developmental |
| Events | |
| Anomaly | ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Published Material / Policy |
Narrative:
Aircraft X was coming from the north at FL280 southbound. Aircraft Y coming from the east westbound at FL300. The rides were choppy from FL290 through FL330 so we knew in advance that the aircraft Y would be asking for lower. Trainee got control from sector 39 to descend aircraft X in anticipation of this. Descended aircraft X from FL280 to FL240 just then aircraft Y asked for lower for the ride. I saw aircraft X leave FL280 and passing FL278 when trainee issued descent to FL280 to aircraft Y. Trainee has been recommended for certification skills check at this sector and is very competent. I was then distracted from the sector and took my attention away from the scope. I heard the trainee issue the next clearance to FL260 to aircraft Y. I then noticed conflict alert going off and I questioned the trainee. He informed me that he used vacated altitudes and I figured it was all good. After being relieved from the sector we were doing a debriefing on his training from the day and he informed me that he may have messed up on the vacated altitudes. He wasn't sure if he transposed the altitude form FL265 for FL256. That is when I informed him to fill out a report as I would do the same.no recommendation I can think of. I let my guard down as traffic was slow and I have worked with this trainee on numerous occasions. I saw him use vacated altitudes earlier with these two aircraft and did not observe him the second time when he descended aircraft Y to FL260. When I saw the conflict alert go off and I asked him and he replied he used vacated; I assumed he did but I was not 100 percent certain. As traffic was slow I let my attention wander.
Original NASA ASRS Text
Title: Reporters write about loss of separation due to improper use of Vacated Altitude separation rule; leading to a loss of separation.
Narrative: Aircraft X was coming from the north at FL280 southbound. Aircraft Y coming from the east westbound at FL300. The rides were choppy from FL290 through FL330 so we knew in advance that the Aircraft Y would be asking for lower. Trainee got control from Sector 39 to descend Aircraft X in anticipation of this. Descended Aircraft X from FL280 to FL240 just then Aircraft Y asked for lower for the ride. I saw Aircraft X leave FL280 and passing FL278 when trainee issued descent to FL280 to Aircraft Y. Trainee has been recommended for certification skills check at this sector and is very competent. I was then distracted from the sector and took my attention away from the scope. I heard the trainee issue the next clearance to FL260 to Aircraft Y. I then noticed conflict alert going off and I questioned the trainee. He informed me that he used vacated altitudes and I figured it was all good. After being relieved from the sector we were doing a debriefing on his training from the day and he informed me that he may have messed up on the vacated altitudes. He wasn't sure if he transposed the altitude form FL265 for FL256. That is when I informed him to fill out a report as I would do the same.No recommendation I can think of. I let my guard down as traffic was slow and I have worked with this trainee on numerous occasions. I saw him use vacated altitudes earlier with these two aircraft and did not observe him the second time when he descended Aircraft Y to FL260. When I saw the conflict alert go off and I asked him and he replied he used vacated; I assumed he did but I was not 100 percent certain. As traffic was slow I let my attention wander.
Data retrieved from NASA's ASRS site 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.