Narrative:

In clear air at FL330, above a layer (in some mountain wave activity) mostly smooth air, we elected to keep seat belt sign illuminated and made a PA to advise passenger that we wished them to remain seated with seat belts on. In mostly smooth air we felt a small smooth aircraft attitude change followed almost immediately by a sharp jolt or 2 which caused the aircraft to roll left and right approximately 20 degrees and to pitch up and down rapidly, followed just as quickly by continued smooth air as we had experienced prior to the clear air turbulence. During the event, the autoplt disconnected and the captain had his hands on the yoke kept the deviations of attitude to those described. After the incident the aircraft flew normally and the autoplt was reconnected without further incident. We reported to ATC our experience and subsequently other aircraft in that approximately place also reported some turbulence of significance. There had been a fairly significant WX system moving through the area. We were cruising at FL330, speed .76 mach. One flight attendant and 2 passenger were hurt when they hit the ceiling. The 2 passenger were not wearing seat belts at the time. One had been in the bathroom and another had been in her seat. At smf paramedics removed the passenger for observation in the local hospital. Aircraft was inspected for damage and returned to service.

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Original NASA ASRS Text

Title: CLR AIR TURB SEAT BELT ON. NO PREVIOUS RPTS.

Narrative: IN CLR AIR AT FL330, ABOVE A LAYER (IN SOME MOUNTAIN WAVE ACTIVITY) MOSTLY SMOOTH AIR, WE ELECTED TO KEEP SEAT BELT SIGN ILLUMINATED AND MADE A PA TO ADVISE PAX THAT WE WISHED THEM TO REMAIN SEATED WITH SEAT BELTS ON. IN MOSTLY SMOOTH AIR WE FELT A SMALL SMOOTH ACFT ATTITUDE CHANGE FOLLOWED ALMOST IMMEDIATELY BY A SHARP JOLT OR 2 WHICH CAUSED THE ACFT TO ROLL L AND R APPROX 20 DEGS AND TO PITCH UP AND DOWN RAPIDLY, FOLLOWED JUST AS QUICKLY BY CONTINUED SMOOTH AIR AS WE HAD EXPERIENCED PRIOR TO THE CLR AIR TURB. DURING THE EVENT, THE AUTOPLT DISCONNECTED AND THE CAPT HAD HIS HANDS ON THE YOKE KEPT THE DEVS OF ATTITUDE TO THOSE DESCRIBED. AFTER THE INCIDENT THE ACFT FLEW NORMALLY AND THE AUTOPLT WAS RECONNECTED WITHOUT FURTHER INCIDENT. WE RPTED TO ATC OUR EXPERIENCE AND SUBSEQUENTLY OTHER ACFT IN THAT APPROX PLACE ALSO RPTED SOME TURB OF SIGNIFICANCE. THERE HAD BEEN A FAIRLY SIGNIFICANT WX SYS MOVING THROUGH THE AREA. WE WERE CRUISING AT FL330, SPD .76 MACH. ONE FLT ATTENDANT AND 2 PAX WERE HURT WHEN THEY HIT THE CEILING. THE 2 PAX WERE NOT WEARING SEAT BELTS AT THE TIME. ONE HAD BEEN IN THE BATHROOM AND ANOTHER HAD BEEN IN HER SEAT. AT SMF PARAMEDICS REMOVED THE PAX FOR OBSERVATION IN THE LCL HOSPITAL. ACFT WAS INSPECTED FOR DAMAGE AND RETURNED TO SVC.

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.