Narrative:

In cruise at FL330, in smooth, VMC conditions, ATC advised us of moderate mountain wave activity associated with light turbulence ahead and for the next 40 mi. In preparation, the flight attendants were warned over the interphone of possible choppy air and the ignition was placed in continuous. Approximately 3 mins later we encountered light mountain wave activity with no airspeed changes and plus or minus 300 FPM vertical speed changes within 5 seconds this was followed by a rapid and violent updraft (vertical speed at 6000 FPM up) with the airspeed increasing rapidly. The captain notified ATC that we were unable to maintain altitude. I disconnected the autothrottle, in an attempt to arrest the airspeed from increasing, and finally the throttles were placed at idle, airspeed was about 10-15 KTS above barber pole, pitch attitude about 7 degrees nose up and the aircraft was still climbing rapidly. The climb was finally arrested at FL345. The captain made a PA announcement for the passenger and flight attendants to take their seats. The climb was followed by a rapid descent (6000 FPM down) with the airspeed decreasing to 230 KIAS. My concern was not to over stress the aircraft with fast elevator movements. The aircraft was now leveled at FL315 and ATC was advised that we were attempting a climb back to FL330. We encountered no further mountain wave activity or turbulence. The autoplt appeared to have disconnected by itself during the initial updraft. Before we were able to talk again to ATC, ATC made a general announcement that the mountain wave activity was severe. The captain then informed ATC that they should not allow other aircraft to proceed at that altitude over the same area. We were then cleared to descend to FL290. We received a call from the first flight attendant, that there was one flight attendant injured and that there was one passenger using oxygen. Captain directed the flight attendant to locate a doctor to attend to the passenger and flight attendant, and it was so done. The company, dispatch, maintenance were notified and a logbook write-up was made requiring a severe turbulence inspection of the aircraft on arrival which was so done. Paramedics awaited the flight where the 1 passenger was released home and the flight attendant was taken to the hospital for precautionary x-rays, yet no problems were found. I believe that other aircraft involved previous to us should have been more descriptive of the conditions and ATC should have used the word moderate turbulence associated with mountain wave, instead of light.

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Original NASA ASRS Text

Title: AN MLG CAUGHT IN A MOUNTAIN WAVE WIND CONDITION RESULTED IN MINOR INJURIES TO ONE CABIN AND PAX.

Narrative: IN CRUISE AT FL330, IN SMOOTH, VMC CONDITIONS, ATC ADVISED US OF MODERATE MOUNTAIN WAVE ACTIVITY ASSOCIATED WITH LIGHT TURB AHEAD AND FOR THE NEXT 40 MI. IN PREPARATION, THE FLT ATTENDANTS WERE WARNED OVER THE INTERPHONE OF POSSIBLE CHOPPY AIR AND THE IGNITION WAS PLACED IN CONTINUOUS. APPROX 3 MINS LATER WE ENCOUNTERED LIGHT MOUNTAIN WAVE ACTIVITY WITH NO AIRSPD CHANGES AND PLUS OR MINUS 300 FPM VERT SPD CHANGES WITHIN 5 SECONDS THIS WAS FOLLOWED BY A RAPID AND VIOLENT UPDRAFT (VERT SPD AT 6000 FPM UP) WITH THE AIRSPD INCREASING RAPIDLY. THE CAPT NOTIFIED ATC THAT WE WERE UNABLE TO MAINTAIN ALT. I DISCONNECTED THE AUTOTHROTTLE, IN AN ATTEMPT TO ARREST THE AIRSPD FROM INCREASING, AND FINALLY THE THROTTLES WERE PLACED AT IDLE, AIRSPD WAS ABOUT 10-15 KTS ABOVE BARBER POLE, PITCH ATTITUDE ABOUT 7 DEGS NOSE UP AND THE ACFT WAS STILL CLBING RAPIDLY. THE CLB WAS FINALLY ARRESTED AT FL345. THE CAPT MADE A PA ANNOUNCEMENT FOR THE PAX AND FLT ATTENDANTS TO TAKE THEIR SEATS. THE CLB WAS FOLLOWED BY A RAPID DSCNT (6000 FPM DOWN) WITH THE AIRSPD DECREASING TO 230 KIAS. MY CONCERN WAS NOT TO OVER STRESS THE ACFT WITH FAST ELEVATOR MOVEMENTS. THE ACFT WAS NOW LEVELED AT FL315 AND ATC WAS ADVISED THAT WE WERE ATTEMPTING A CLB BACK TO FL330. WE ENCOUNTERED NO FURTHER MOUNTAIN WAVE ACTIVITY OR TURB. THE AUTOPLT APPEARED TO HAVE DISCONNECTED BY ITSELF DURING THE INITIAL UPDRAFT. BEFORE WE WERE ABLE TO TALK AGAIN TO ATC, ATC MADE A GENERAL ANNOUNCEMENT THAT THE MOUNTAIN WAVE ACTIVITY WAS SEVERE. THE CAPT THEN INFORMED ATC THAT THEY SHOULD NOT ALLOW OTHER ACFT TO PROCEED AT THAT ALT OVER THE SAME AREA. WE WERE THEN CLRED TO DSND TO FL290. WE RECEIVED A CALL FROM THE FIRST FLT ATTENDANT, THAT THERE WAS ONE FLT ATTENDANT INJURED AND THAT THERE WAS ONE PAX USING OXYGEN. CAPT DIRECTED THE FLT ATTENDANT TO LOCATE A DOCTOR TO ATTEND TO THE PAX AND FLT ATTENDANT, AND IT WAS SO DONE. THE COMPANY, DISPATCH, MAINT WERE NOTIFIED AND A LOGBOOK WRITE-UP WAS MADE REQUIRING A SEVERE TURB INSPECTION OF THE ACFT ON ARR WHICH WAS SO DONE. PARAMEDICS AWAITED THE FLT WHERE THE 1 PAX WAS RELEASED HOME AND THE FLT ATTENDANT WAS TAKEN TO THE HOSPITAL FOR PRECAUTIONARY X-RAYS, YET NO PROBS WERE FOUND. I BELIEVE THAT OTHER ACFT INVOLVED PREVIOUS TO US SHOULD HAVE BEEN MORE DESCRIPTIVE OF THE CONDITIONS AND ATC SHOULD HAVE USED THE WORD MODERATE TURB ASSOCIATED WITH MOUNTAIN WAVE, INSTEAD OF LIGHT.

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.