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B737-700 flight crew reported being unable to maintain altitude during an encounter with a severe mountain wave over the rockies.
| Attributes | |
| ACN | 1542186 |
| Time | |
| Date | 201805 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | PUB.Airport |
| State Reference | CO |
| Environment | |
| Flight Conditions | Mixed |
| Light | Night |
| Aircraft 1 | |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Cruise |
| Flight Plan | IFR |
| Person 1 | |
| Function | Captain Pilot Not Flying |
| Qualification | Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument |
| Experience | Flight Crew Last 90 Days 501 |
| Person 2 | |
| Function | First Officer Pilot Flying |
| Qualification | Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 449 |
| Events | |
| Anomaly | Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter Weather / Turbulence |
Narrative:
Starting at 40 miles west of publication; we encountered mountain wave. We were unable to maintain altitude at FL390. The aircraft deviated from FL394 to FL363. We received an initial block altitude from den center from FL400 to FL380. We received a secondary bout of waves and were then descending at 4400 fpm to keep the aircraft from stalling and recovered at the lowest altitude as stated above. Even after recovering altitude; it still took a prolonged period of time to regain our airspeed to .78 mach before attempting to climb back to our altitude of FL390. The entire event lasted for approximately four minutes. There was nothing that could have been done to prevent this in that it was not associated with a specific weather system; was not the fault of ATC; nor was there the means by which we could have anticipated the extent of the turbulence and the effect on our aircraft.
Original NASA ASRS Text
Title: B737-700 flight crew reported being unable to maintain altitude during an encounter with a severe mountain wave over the Rockies.
Narrative: Starting at 40 miles west of PUB; we encountered mountain wave. We were unable to maintain altitude at FL390. The aircraft deviated from FL394 to FL363. We received an initial block altitude from DEN Center from FL400 to FL380. We received a secondary bout of waves and were then descending at 4400 fpm to keep the aircraft from stalling and recovered at the lowest altitude as stated above. Even after recovering altitude; it still took a prolonged period of time to regain our airspeed to .78 Mach before attempting to climb back to our altitude of FL390. The entire event lasted for approximately four minutes. There was nothing that could have been done to prevent this in that it was not associated with a specific weather system; was not the fault of ATC; nor was there the means by which we could have anticipated the extent of the turbulence and the effect on our aircraft.
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.