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Captain of an medium large transport briefly lost control of aircraft due to encounter with mountain wave turbulence resulting in loss of altitude and airspeed.
| Attributes | |
| ACN | 427628 |
| Time | |
| Date | 199902 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : den |
| State Reference | CO |
| Altitude | msl bound lower : 30000 msl bound upper : 32000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute airway : zdv |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : flight engineer pilot : cfi |
| Experience | flight time last 90 days : 200 flight time total : 14000 flight time type : 5000 |
| ASRS Report | 427628 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 120 flight time total : 5000 flight time type : 300 |
| ASRS Report | 427512 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude other anomaly other |
| Independent Detector | other flight crewa |
| Consequence | Other |
| Supplementary | |
| Air Traffic Incident | other |
Narrative:
Climbed to FL310 out of denver. Reports of moderate to severe turbulence above FL350. We had just leveled off at FL310 50 DME west of denver. Was moderate turbulence on climb, smooth at FL310. Started to notice some extreme mountain wave +/-10-15 KTS. Told flight attendants to be seated. Saw +/-1000 ft vertical speed fluctuations. Disconnected autothrottles. Then the severe turbulence hit. Autoplt was engaged. Aircraft was jolted severely, lost 700 ft altitude. Disengaged autoplt to regain control of aircraft. Notified ATC. ATC claimed no traffic conflict. Checked on passenger and crew, no one hurt. Contacted dispatch with severe turbulence report. Wrote up maintenance logbook write-up about encounter. We could not have foreseen this encounter since we were the first aircraft of the morning heading west out of denver. The forecasts were showing the potential but no PIREPS yet.
Original NASA ASRS Text
Title: CAPT OF AN MLG BRIEFLY LOST CTL OF ACFT DUE TO ENCOUNTER WITH MOUNTAIN WAVE TURB RESULTING IN LOSS OF ALT AND AIRSPD.
Narrative: CLBED TO FL310 OUT OF DENVER. RPTS OF MODERATE TO SEVERE TURB ABOVE FL350. WE HAD JUST LEVELED OFF AT FL310 50 DME W OF DENVER. WAS MODERATE TURB ON CLB, SMOOTH AT FL310. STARTED TO NOTICE SOME EXTREME MOUNTAIN WAVE +/-10-15 KTS. TOLD FLT ATTENDANTS TO BE SEATED. SAW +/-1000 FT VERT SPD FLUCTUATIONS. DISCONNECTED AUTOTHROTTLES. THEN THE SEVERE TURB HIT. AUTOPLT WAS ENGAGED. ACFT WAS JOLTED SEVERELY, LOST 700 FT ALT. DISENGAGED AUTOPLT TO REGAIN CTL OF ACFT. NOTIFIED ATC. ATC CLAIMED NO TFC CONFLICT. CHKED ON PAX AND CREW, NO ONE HURT. CONTACTED DISPATCH WITH SEVERE TURB RPT. WROTE UP MAINT LOGBOOK WRITE-UP ABOUT ENCOUNTER. WE COULD NOT HAVE FORESEEN THIS ENCOUNTER SINCE WE WERE THE FIRST ACFT OF THE MORNING HDG W OUT OF DENVER. THE FORECASTS WERE SHOWING THE POTENTIAL BUT NO PIREPS YET.
Data retrieved from NASA's ASRS site as of July 2007 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.