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Los angeles center controller reported of a loss of separation between two aircraft under his control. Pilot thought there were to descend for a crossing restriction; but was told by ATC to maintain a specific altitude.
| Attributes | |
| ACN | 1383050 |
| Time | |
| Date | 201608 |
| Local Time Of Day | 0001-0600 |
| Place | |
| Locale Reference | ZLA.ARTCC |
| State Reference | CA |
| Aircraft 1 | |
| Make Model Name | B737-800 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | A319 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Climb |
| Flight Plan | IFR |
| Person 1 | |
| Function | Enroute |
| Qualification | Air Traffic Control Fully Certified |
| Experience | Air Traffic Control Time Certified In Pos 1 (mon) 2 Air Traffic Control Time Certified In Pos 1 (yrs) 1 |
| Events | |
| Anomaly | ATC Issue All Types Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance |
Narrative:
This is a pilot deviation. I had instructed aircraft X; 'aircraft X; descend to FL350; then cross 10 miles north of pmd at and maintain FL240.' he read back a correct read back. After rescanning the situation and finding a conflict; I decided to change my course of action. At this point; aircraft X depicted that it was descending out of FL353. I then instructed aircraft X; 'aircraft X; amend altitude; descend and maintain FL350.' the pilot read back; 'ok; we're leveling at FL350.' 20 miles later; aircraft X was passing aircraft Y at FL340; waiting to climb to their requested final altitude of FL380. Conflict alert then started to go off between both aircraft; and I immediately asked aircraft X to verify the assigned altitude of FL350. The pilot said he was descending to comply with the crossing restriction. I immediately then called the traffic for aircraft Y; by then; aircraft Y responded that they were responding to an RA and descending. Aircraft X then stated they were responding to an RA and climbing. There was a loss of standard separation. Once they were more than 5 miles apart horizontally; I climbed aircraft Y; and descended aircraft X for the crossing restriction.the pilots need to understand standard phraseology. During a busy situation; controllers don't have time to double check the pilots understand standard phraseology.
Original NASA ASRS Text
Title: Los Angeles Center Controller reported of a loss of separation between two aircraft under his control. Pilot thought there were to descend for a crossing restriction; but was told by ATC to maintain a specific altitude.
Narrative: This is a pilot deviation. I had instructed Aircraft X; 'Aircraft X; Descend to FL350; then cross 10 miles north of PMD at and maintain FL240.' He read back a correct read back. After rescanning the situation and finding a conflict; I decided to change my course of action. At this point; Aircraft X depicted that it was descending out of FL353. I then instructed Aircraft X; 'Aircraft X; Amend altitude; descend and maintain FL350.' The pilot read back; 'Ok; we're leveling at FL350.' 20 miles later; Aircraft X was passing Aircraft Y at FL340; waiting to climb to their requested final altitude of FL380. Conflict alert then started to go off between both aircraft; and I immediately asked Aircraft X to verify the assigned altitude of FL350. The pilot said he was descending to comply with the crossing restriction. I immediately then called the traffic for Aircraft Y; by then; Aircraft Y responded that they were responding to an RA and descending. Aircraft X then stated they were responding to an RA and climbing. There was a loss of standard separation. Once they were more than 5 miles apart horizontally; I climbed Aircraft Y; and descended Aircraft X for the crossing restriction.The pilots need to understand standard phraseology. During a busy situation; controllers don't have time to double check the pilots understand standard phraseology.
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.