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ZKC controller reported an MD11 descended unexpectedly; possibly due to weather phenomena; without alerting ATC.
| Attributes | |
| ACN | 1542516 |
| Time | |
| Date | 201805 |
| Local Time Of Day | 1801-2400 |
| Place | |
| Locale Reference | ZKC.ARTCC |
| State Reference | KS |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | MD-11 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Route In Use | Direct |
| Flight Plan | IFR |
| Person 1 | |
| Function | Enroute |
| Qualification | Air Traffic Control Fully Certified |
| Experience | Air Traffic Control Time Certified In Pos 1 (yrs) 4 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter Weather / Turbulence |
Narrative:
Airplane X descended unexpectedly from FL370 to FL359 before [advising] for a 'stall warning indication;' and then requested lower. I was able to give a pd (profile descent) clearance to FL300 and fortunately there was not a loss of separation. The aircraft was routed direct due to [weather]; and was assigned mach .80 for sequencing. There were areas of mod-extreme precipitation to the aircraft's 1 to 2 o'clock and additional areas at 10 to 11 o'clock. The aircraft was given the specific route to fly; which would take the aircraft through a gap in the [weather] as were other aircraft I was sequencing. After watching the replay; I noticed the aircraft's ground speed diminish from 492 KTS to around 370 KTS in the span of about 7 minutes before the aircraft began descending. At no point did the aircraft advise they were experiencing any turbulence; or that they would need to slow down. However; given the proximity to the convective activity; it is possible that a strong wind shift/shear existed that was not previously made aware to me.I do not have any recommendations other than a [timelier] advisory by the pilot that they either needed to slow down; were encountering turbulence; or encountering wind shear and could not maintain altitude. Though; I understand that flying the plane is most important and communicating is a second priority.
Original NASA ASRS Text
Title: ZKC controller reported an MD11 descended unexpectedly; possibly due to weather phenomena; without alerting ATC.
Narrative: Airplane X descended unexpectedly from FL370 to FL359 before [advising] for a 'stall warning indication;' and then requested lower. I was able to give a PD (Profile Descent) clearance to FL300 and fortunately there was not a loss of separation. The aircraft was routed direct due to [weather]; and was assigned MACH .80 for sequencing. There were areas of MOD-EXTREME precipitation to the aircraft's 1 to 2 o'clock and additional areas at 10 to 11 o'clock. The aircraft was given the specific route to fly; which would take the aircraft through a gap in the [weather] as were other aircraft I was sequencing. After watching the replay; I noticed the aircraft's ground speed diminish from 492 KTS to around 370 KTS in the span of about 7 minutes before the aircraft began descending. At no point did the aircraft advise they were experiencing any turbulence; or that they would need to slow down. However; given the proximity to the convective activity; it is possible that a strong wind shift/shear existed that was not previously made aware to me.I do not have any recommendations other than a [timelier] advisory by the pilot that they either needed to slow down; were encountering turbulence; or encountering wind shear and could not maintain altitude. Though; I understand that flying the plane is most important and communicating is a second priority.
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.