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Enroute controller described a loss of separation event when an aircraft was unable to maintain assigned altitude due to weather.
| Attributes | |
| ACN | 960331 |
| Time | |
| Date | 201107 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.ARTCC |
| State Reference | US |
| Aircraft 1 | |
| Make Model Name | Baron 58/58TC |
| Operating Under FAR Part | Part 91 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Person 1 | |
| Function | Enroute |
| Qualification | Air Traffic Control Developmental |
| Person 2 | |
| Function | Pilot Flying Single Pilot |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine Flight Crew Flight Instructor |
| Experience | Flight Crew Last 90 Days 25 Flight Crew Total 4000 Flight Crew Type 2500 |
| Events | |
| Anomaly | ATC Issue All Types Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter Weather / Turbulence |
Narrative:
There was weather in the sector about 15 miles in diameter and no aircraft were going through it. All westbound aircraft entered the sector deviating left. Midway arrivals; which usually go though another sector; were being rerouted through our sector because of this line of weather; they were entering the sector at 17;000 ft; 250 KTS; and also deviating to the left when able direct to the next fix. Aircraft X entered the sector at 16;000 ft; westbound deviating to the left; aircraft Y entered the sector at 17;000 ft and was deviating left. Aircraft X began turning just south of aircraft Y. Once they were within 5 miles of aircraft Y; aircraft 1 showed 3;000 ft above the assigned altitude. The r-side controller caught this right away and stated to aircraft X they were showing 3;000 above altitude and to confirm they were level at 16;000 ft. Aircraft X did not respond to the controller. Then the aircraft showed at 16;500 ft. At that point; the radar controller restated to the aircraft they were now showing 500 ft above altitude and to confirm they were level at 16;000 ft. Aircraft X finally responded and stated they were descending back to 16;000 ft. At this point the aircraft were about 3 miles apart; aircraft X headed northwest bound and aircraft Y still deviating left of course; westbound. After about a minute; aircraft X reported they were in a bad cloud with hail and the conditions that got really bad. The radar controller then told the aircraft next time they had to tell the controller if they were not able to hold altitude and that an aircraft was right above them at 17;000 ft. The only recommendation would be that the radar controller should have called traffic for the two aircraft. But they were not traffic until aircraft X turned. I do not believe the radar controller realized the aircraft began to turn back and the aircraft X did not state this to the controller.
Original NASA ASRS Text
Title: Enroute Controller described a loss of separation event when an aircraft was unable to maintain assigned altitude due to weather.
Narrative: There was weather in the sector about 15 miles in diameter and no aircraft were going through it. All westbound aircraft entered the sector deviating left. Midway arrivals; which usually go though another sector; were being rerouted through our sector because of this line of weather; they were entering the sector at 17;000 FT; 250 KTS; and also deviating to the left when able direct to the next fix. Aircraft X entered the sector at 16;000 FT; westbound deviating to the left; Aircraft Y entered the sector at 17;000 FT and was deviating left. Aircraft X began turning just south of Aircraft Y. Once they were within 5 miles of Aircraft Y; aircraft 1 showed 3;000 FT above the assigned altitude. The R-Side Controller caught this right away and stated to Aircraft X they were showing 3;000 above altitude and to confirm they were level at 16;000 FT. Aircraft X did not respond to the Controller. Then the aircraft showed at 16;500 FT. At that point; the RADAR Controller restated to the aircraft they were now showing 500 FT above altitude and to confirm they were level at 16;000 FT. Aircraft X finally responded and stated they were descending back to 16;000 FT. At this point the aircraft were about 3 miles apart; Aircraft X headed northwest bound and Aircraft Y still deviating left of course; westbound. After about a minute; Aircraft X reported they were in a bad cloud with hail and the conditions that got really bad. The RADAR Controller then told the aircraft next time they had to tell the Controller if they were not able to hold altitude and that an aircraft was right above them at 17;000 FT. The only recommendation would be that the RADAR Controller should have called traffic for the two aircraft. But they were not traffic until Aircraft X turned. I do not believe the RADAR Controller realized the aircraft began to turn back and the Aircraft X did not state this to the Controller.
Data retrieved from NASA's ASRS site as of April 2012 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.