A B737-800 encountered a mountain wave encounter that caused large airspeed and altitude excursions.

Attributes
ACN	1012023
Time
Date	201205
Local Time Of Day	0601-1200
Place
Locale Reference	ZAB.ARTCC
State Reference	NM
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Flying
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

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.

Original NASA ASRS Text

Title: A B737-800 encountered a mountain wave encounter that caused large airspeed and altitude excursions.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 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.