B737-800
Flight Crew Air Transport Pilot (ATP)
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action
Aircraft; Weather
In cruise FL390 we encountered strong wave action over ABQ VOR. Airspeed increased 10 KTS and altitude increased plus 200 FT. The autoflight system corrected with a large thrust reduction. Then our airspeed dropped 30 KTS and altitude dropped 400 FT from our peak. We nosed the aircraft down in an effort to maintain airspeed. I called ATC and advised them of our immediate descent. We encountered moderate turbulence during the descent. We leveled at FL370. No injuries to passengers or crew because they were seated and galleys were secure. No airframe limits were reached. No traffic conflicts were encountered.
The mountain wave had been reported as moderate; but I thought our experience was moderate to severe.
A B737-800 encountered a mountain wave encounter that caused large airspeed and altitude excursions.