Narrative:

Flying in the vicinity of laa VOR; we had just climbed to FL350 attempting to clear clouds and find a better ride. We began to encounter moderate mountain wave along with light turbulence and our airspeed was fluctuating +/-25 KTS. While we were below the recommended maximum altitude for our weight; and well within the 1.3 G buffet envelope; we were unable to maintain a safe speed and advised ATC we were unable to maintain altitude and that we were beginning a descent. We began a descent out of FL350 and received a clearance to FL330 while descending through FL344. We started the descent before being issued a clearance because the aircraft had slowed below what we considered to be a safe speed (vls 10/15 KTS) even with maximum continuous thrust being applied. The aircraft was coming down with or without a clearance. There were no targets close by on the TCAS and there was no conflict with other traffic. In 27 yrs of flying jet aircraft; this has never happened to me. We did everything right. We were not trying to fly the aircraft beyond its capabilities. We were well within the proper flight envelope. It's just one of those things that can happen. Mountain wave and turbulence can put you outside the safe envelope in a hurry. Winds aloft were unusually strong. You don't usually encounter waves that strong this late in the season.

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Original NASA ASRS Text

Title: AN A320 ACFT ENCOUNTERED MOUNTAIN WAVE; DECELERATED; AND BEGAN DESCENDING WITH MAX CONTINUOUS THRUST BEFORE ATC DESCENT CLRNC WAS RECEIVED.

Narrative: FLYING IN THE VICINITY OF LAA VOR; WE HAD JUST CLBED TO FL350 ATTEMPTING TO CLR CLOUDS AND FIND A BETTER RIDE. WE BEGAN TO ENCOUNTER MODERATE MOUNTAIN WAVE ALONG WITH LIGHT TURB AND OUR AIRSPD WAS FLUCTUATING +/-25 KTS. WHILE WE WERE BELOW THE RECOMMENDED MAX ALT FOR OUR WT; AND WELL WITHIN THE 1.3 G BUFFET ENVELOPE; WE WERE UNABLE TO MAINTAIN A SAFE SPD AND ADVISED ATC WE WERE UNABLE TO MAINTAIN ALT AND THAT WE WERE BEGINNING A DSCNT. WE BEGAN A DSCNT OUT OF FL350 AND RECEIVED A CLRNC TO FL330 WHILE DSNDING THROUGH FL344. WE STARTED THE DSCNT BEFORE BEING ISSUED A CLRNC BECAUSE THE ACFT HAD SLOWED BELOW WHAT WE CONSIDERED TO BE A SAFE SPD (VLS 10/15 KTS) EVEN WITH MAX CONTINUOUS THRUST BEING APPLIED. THE ACFT WAS COMING DOWN WITH OR WITHOUT A CLRNC. THERE WERE NO TARGETS CLOSE BY ON THE TCAS AND THERE WAS NO CONFLICT WITH OTHER TFC. IN 27 YRS OF FLYING JET ACFT; THIS HAS NEVER HAPPENED TO ME. WE DID EVERYTHING RIGHT. WE WERE NOT TRYING TO FLY THE ACFT BEYOND ITS CAPABILITIES. WE WERE WELL WITHIN THE PROPER FLT ENVELOPE. IT'S JUST ONE OF THOSE THINGS THAT CAN HAPPEN. MOUNTAIN WAVE AND TURB CAN PUT YOU OUTSIDE THE SAFE ENVELOPE IN A HURRY. WINDS ALOFT WERE UNUSUALLY STRONG. YOU DON'T USUALLY ENCOUNTER WAVES THAT STRONG THIS LATE IN THE SEASON.

Data retrieved from NASA's ASRS site as of May 2009 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.