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B737-700 encounters mountain wave and moderate turbulence at FL380. Mach deteriorates to stick shaker and descent must be made to regain airspeed.
| Attributes | |
| ACN | 682111 |
| Time | |
| Date | 200512 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : abq.airport |
| State Reference | NM |
| Altitude | msl single value : 36000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zab.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| ASRS Report | 682111 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter : turbulence inflight encounter other other anomaly |
| Independent Detector | aircraft equipment other aircraft equipment : stick shaker other flight crewa |
| Resolutory Action | flight crew : exited adverse environment other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Weather Aircraft Chart Or Publication |
| Primary Problem | Weather |
Narrative:
Turbulence reports were being received in the area from ZAB and other aircraft. We asked for and climbed to FL380 (we were at cruise at FL360). The FMC indicated FL380 was below optimum. I looked ahead and saw lenticular clouds just before this incident. I had just seated the flight attendants about 30 seconds before using the PA. Right after seating the attendants; we incurred moderate turbulence and mountain wave at exactly the same time. The indicated airspeed went from about .74 mach to the yellow indication on the masi with associated stick shaker warning in about a second or less. I reacted with emergency thrust and autoplt disengagement. We requested a lower flight level immediately and descended to FL340. During the descent; we were able to increase the airspeed and get out of the mountain wave and turbulence. No emergency was declared and no ATC deviation occurred.
Original NASA ASRS Text
Title: B737-700 ENCOUNTERS MOUNTAIN WAVE AND MODERATE TURB AT FL380. MACH DETERIORATES TO STICK SHAKER AND DSCNT MUST BE MADE TO REGAIN AIRSPD.
Narrative: TURB RPTS WERE BEING RECEIVED IN THE AREA FROM ZAB AND OTHER ACFT. WE ASKED FOR AND CLBED TO FL380 (WE WERE AT CRUISE AT FL360). THE FMC INDICATED FL380 WAS BELOW OPTIMUM. I LOOKED AHEAD AND SAW LENTICULAR CLOUDS JUST BEFORE THIS INCIDENT. I HAD JUST SEATED THE FLT ATTENDANTS ABOUT 30 SECONDS BEFORE USING THE PA. RIGHT AFTER SEATING THE ATTENDANTS; WE INCURRED MODERATE TURB AND MOUNTAIN WAVE AT EXACTLY THE SAME TIME. THE INDICATED AIRSPD WENT FROM ABOUT .74 MACH TO THE YELLOW INDICATION ON THE MASI WITH ASSOCIATED STICK SHAKER WARNING IN ABOUT A SECOND OR LESS. I REACTED WITH EMER THRUST AND AUTOPLT DISENGAGEMENT. WE REQUESTED A LOWER FLT LEVEL IMMEDIATELY AND DSNDED TO FL340. DURING THE DSCNT; WE WERE ABLE TO INCREASE THE AIRSPD AND GET OUT OF THE MOUNTAIN WAVE AND TURB. NO EMER WAS DECLARED AND NO ATC DEV OCCURRED.
Data retrieved from NASA's ASRS site as of January 2009 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.