A 320 crew encountered moderate to severe mountain wave activity in ZLC class a airspace.

Attributes
ACN	537831
Time
Date	200202
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : hve.vortac
State Reference	UT
Altitude	msl single value : 37000
Environment
Flight Conditions	VMC
Weather Elements	Turbulence other
Aircraft 1
Controlling Facilities	artcc : zlc.artcc artcc : zjx.artcc
Operator	common carrier : air carrier
Make Model Name	A320
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
Qualification	pilot : atp
ASRS Report	537831
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : turbulence inflight encounter : weather inflight encounter other other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : returned to original clearance none taken : anomaly accepted none taken : detected after the fact
Consequence	other other
Supplementary
Problem Areas	Weather
Primary Problem	Weather

Narrative:

Turbulence reports were intermittent light chop, due to report, mach was reduced from .80 mach to .77 mach when moderate to severe mountain wave occurred. This caused a rapid increase in airspeed. The throttles were reduced to idle and autoplt was disengaged. A slight nose up input was applied to control the airspeed. In spite of the corrective action, a slight overspd occurred (3 KTS, 2 seconds). Also, altitude deviation was +300 ft to 600-700 ft loss. ATC notified. They reported no traffic conflicts and to climb to FL370 when able. Seatbelt sign was on and flight attendants/passenger seated -- no injuries. Dispatch notified and a write-up was made in maintenance logbook.

Original NASA ASRS Text

Title: A 320 CREW ENCOUNTERED MODERATE TO SEVERE MOUNTAIN WAVE ACTIVITY IN ZLC CLASS A AIRSPACE.

Narrative: TURB RPTS WERE INTERMITTENT LIGHT CHOP, DUE TO RPT, MACH WAS REDUCED FROM .80 MACH TO .77 MACH WHEN MODERATE TO SEVERE MOUNTAIN WAVE OCCURRED. THIS CAUSED A RAPID INCREASE IN AIRSPD. THE THROTTLES WERE REDUCED TO IDLE AND AUTOPLT WAS DISENGAGED. A SLIGHT NOSE UP INPUT WAS APPLIED TO CTL THE AIRSPD. IN SPITE OF THE CORRECTIVE ACTION, A SLIGHT OVERSPD OCCURRED (3 KTS, 2 SECONDS). ALSO, ALTDEV WAS +300 FT TO 600-700 FT LOSS. ATC NOTIFIED. THEY RPTED NO TFC CONFLICTS AND TO CLB TO FL370 WHEN ABLE. SEATBELT SIGN WAS ON AND FLT ATTENDANTS/PAX SEATED -- NO INJURIES. DISPATCH NOTIFIED AND A WRITE-UP WAS MADE IN MAINT LOGBOOK.

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.