A319 encounters severe mountain wave in ZDV airspace.

Attributes
ACN	423783
Time
Date	199812
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : dbl
State Reference	CO
Altitude	msl bound lower : 37500 msl bound upper : 39000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 100 flight time total : 11000 flight time type : 100
ASRS Report	423783
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude
Independent Detector	other flight crewa
Resolutory Action	flight crew : exited adverse environment
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

At FL390 approximately 50 NM east of dbl VOR, we encountered extremely strong mountain wave (no turbulence) activity. The airspeed rapidly dropped into the V minimum selectable range. I (captain) pushed the throttles to the toga position. The airspeed continued to decrease, and as the airspeed approached the alpha protection zone, I disengaged the autoplt and began a descent of 1000 FPM, still with toga (maximum) thrust. The speed briefly dropped into the alpha protection zone, but did not activate the alpha protection features. At approximately FL370 the airspeed began to increase, and we accelerated out of the V minimum selectable zone. Before leaving FL390, we attempted to advise ATC of our problem, but radio congestion did not allow us to report the deviation until we were at approximately FL375 to FL370. The first officer did check for traffic visually and with the TCASII display. ATC was advised and then cleared us to FL350. There were no ATC reports of mountain wave to that point.

Original NASA ASRS Text

Title: A319 ENCOUNTERS SEVERE MOUNTAIN WAVE IN ZDV AIRSPACE.

Narrative: AT FL390 APPROX 50 NM E OF DBL VOR, WE ENCOUNTERED EXTREMELY STRONG MOUNTAIN WAVE (NO TURB) ACTIVITY. THE AIRSPD RAPIDLY DROPPED INTO THE V MINIMUM SELECTABLE RANGE. I (CAPT) PUSHED THE THROTTLES TO THE TOGA POS. THE AIRSPD CONTINUED TO DECREASE, AND AS THE AIRSPD APCHED THE ALPHA PROTECTION ZONE, I DISENGAGED THE AUTOPLT AND BEGAN A DSCNT OF 1000 FPM, STILL WITH TOGA (MAX) THRUST. THE SPD BRIEFLY DROPPED INTO THE ALPHA PROTECTION ZONE, BUT DID NOT ACTIVATE THE ALPHA PROTECTION FEATURES. AT APPROX FL370 THE AIRSPD BEGAN TO INCREASE, AND WE ACCELERATED OUT OF THE V MINIMUM SELECTABLE ZONE. BEFORE LEAVING FL390, WE ATTEMPTED TO ADVISE ATC OF OUR PROB, BUT RADIO CONGESTION DID NOT ALLOW US TO RPT THE DEV UNTIL WE WERE AT APPROX FL375 TO FL370. THE FO DID CHK FOR TFC VISUALLY AND WITH THE TCASII DISPLAY. ATC WAS ADVISED AND THEN CLRED US TO FL350. THERE WERE NO ATC RPTS OF MOUNTAIN WAVE TO THAT POINT.

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.