An air carrier B757 reports that it got into a mountain wave that lifted the aircraft 300 ft and caused the aircraft to overspeed. WX factors mountain wave, light chop.

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Attributes
ACN	367157
Time
Date	199611
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zzz
State Reference	US
Altitude	msl bound lower : 39000 msl bound upper : 39000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	367157
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance non adherence : published procedure other anomaly
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	other

Narrative:

At FL390, mach .81, with occasional light chop, we encountered moderate to severe mountain wave. Almost instantly and unctlably, the aircraft gained 300 ft and accelerated through the barber pole up to mach .87. We got the overspd warning. Autoplt was disconnected and immediate attempt was made to slow down, but we estimate that we were above redline speed for 15-20 seconds. After consulting with dispatch and maintenance, we continued the flight to miami.

Original NASA ASRS Text

Title: AN ACR B757 RPTS THAT IT GOT INTO A MOUNTAIN WAVE THAT LIFTED THE ACFT 300 FT AND CAUSED THE ACFT TO OVERSPEED. WX FACTORS MOUNTAIN WAVE, LIGHT CHOP.

Narrative: AT FL390, MACH .81, WITH OCCASIONAL LIGHT CHOP, WE ENCOUNTERED MODERATE TO SEVERE MOUNTAIN WAVE. ALMOST INSTANTLY AND UNCTLABLY, THE ACFT GAINED 300 FT AND ACCELERATED THROUGH THE BARBER POLE UP TO MACH .87. WE GOT THE OVERSPD WARNING. AUTOPLT WAS DISCONNECTED AND IMMEDIATE ATTEMPT WAS MADE TO SLOW DOWN, BUT WE ESTIMATE THAT WE WERE ABOVE REDLINE SPD FOR 15-20 SECONDS. AFTER CONSULTING WITH DISPATCH AND MAINT, WE CONTINUED THE FLT TO MIAMI.

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.