Narrative:

IFR flight from den to stl. Route would encounter numerous thunderstorms and line of cumulo nimbus. We successfully navigated through these lines of cumulo nimbus. ZKC changed our arrival from a trake 5 to an atlas 5 arrival to stl. This was due to cumulo nimbus west of stl, and the atlas would give us a northwest arrival. We were proceeding to irk from the atlas 5 arrival. We could see cumulo nimbus south of us and north of our course on radar. As we approached irk our radar showed several strong echoes over the atlas fix. We informed center and he said he could not see them. We asked for a ride report, and he said he had no aircraft in that area for awhile. Our radar showed a clear area south of our present position toward columbia, mo. The cumulo nimbus west of stl were far enough away to allow us to go to columbia and then proceed east to stl. We asked for and received clearance to go to col and pick up the remainder of the trake 5 arrival. I was flying the aircraft on autoplt. I initiated a right turn to col. We were in the clouds and a relatively smooth flight. As the turn continued we temporarily broke out of the clouds and saw a rapidly developing circuit breaker in front of us. There was no indication of this circuit breaker on radar. We had excellent returns on the radar throughout the flight. The passenger were strapped in their seats for most of flight. The captain had informed the flight attendant's of the circuit breaker threat as we approached stl. When I saw the cloud I immediately disengaged the autoplt and increased the angle of bank to avoid. We penetrated the side of the cloud and experienced severe turbulence for about 4-5 seconds. The aircraft climbed rapidly, even though I applied full forward stick. The aircraft responded to control inputs at about 37800 ft. We quickly returned to 37000 ft. This was a very brief encounter. The captain checked the flight attendant's and received a report that one of the rear cabin flight attendant's hurt her arm. We continued our flight to stl and notified ATC of the encounter and asked to have paramedics to meet aircraft at the gate. Flight continued west/O incident. Flight attendant sustained a possible wrist injury. I have not been able to find out exact injury. This encounter was unavoidable since we were unable to detect it on radar. We had done a very good job of navigation through these WX systems. We were on our third arrival clearance change to get to stl. Our decision to go south to col was a good one since it provided a clear area to stl. The aircraft was written up for severe turbulence encounter, and received an inspection by mechanics at stl. No damage to aircraft. Aircraft and pilot crew continued on duty. Company reports were submitted.

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Original NASA ASRS Text

Title: ACR MLG ENCOUNTERS SEVERE TURBULENCE IN TSTM, RESULTING IN MINOR INJURY TO FLT ATTENDANT.

Narrative: IFR FLT FROM DEN TO STL. RTE WOULD ENCOUNTER NUMEROUS TSTMS AND LINE OF CUMULO NIMBUS. WE SUCCESSFULLY NAVIGATED THROUGH THESE LINES OF CUMULO NIMBUS. ZKC CHANGED OUR ARR FROM A TRAKE 5 TO AN ATLAS 5 ARR TO STL. THIS WAS DUE TO CUMULO NIMBUS W OF STL, AND THE ATLAS WOULD GIVE US A NW ARR. WE WERE PROCEEDING TO IRK FROM THE ATLAS 5 ARR. WE COULD SEE CUMULO NIMBUS S OF US AND N OF OUR COURSE ON RADAR. AS WE APCHED IRK OUR RADAR SHOWED SEVERAL STRONG ECHOES OVER THE ATLAS FIX. WE INFORMED CTR AND HE SAID HE COULD NOT SEE THEM. WE ASKED FOR A RIDE RPT, AND HE SAID HE HAD NO ACFT IN THAT AREA FOR AWHILE. OUR RADAR SHOWED A CLR AREA S OF OUR PRESENT POS TOWARD COLUMBIA, MO. THE CUMULO NIMBUS W OF STL WERE FAR ENOUGH AWAY TO ALLOW US TO GO TO COLUMBIA AND THEN PROCEED E TO STL. WE ASKED FOR AND RECEIVED CLRNC TO GO TO COL AND PICK UP THE REMAINDER OF THE TRAKE 5 ARR. I WAS FLYING THE ACFT ON AUTOPLT. I INITIATED A RIGHT TURN TO COL. WE WERE IN THE CLOUDS AND A RELATIVELY SMOOTH FLT. AS THE TURN CONTINUED WE TEMPORARILY BROKE OUT OF THE CLOUDS AND SAW A RAPIDLY DEVELOPING CB IN FRONT OF US. THERE WAS NO INDICATION OF THIS CB ON RADAR. WE HAD EXCELLENT RETURNS ON THE RADAR THROUGHOUT THE FLT. THE PAX WERE STRAPPED IN THEIR SEATS FOR MOST OF FLT. THE CAPT HAD INFORMED THE FLT ATTENDANT'S OF THE CB THREAT AS WE APCHED STL. WHEN I SAW THE CLOUD I IMMEDIATELY DISENGAGED THE AUTOPLT AND INCREASED THE ANGLE OF BANK TO AVOID. WE PENETRATED THE SIDE OF THE CLOUD AND EXPERIENCED SEVERE TURB FOR ABOUT 4-5 SECS. THE ACFT CLBED RAPIDLY, EVEN THOUGH I APPLIED FULL FORWARD STICK. THE ACFT RESPONDED TO CTL INPUTS AT ABOUT 37800 FT. WE QUICKLY RETURNED TO 37000 FT. THIS WAS A VERY BRIEF ENCOUNTER. THE CAPT CHKED THE FLT ATTENDANT'S AND RECEIVED A RPT THAT ONE OF THE REAR CABIN FLT ATTENDANT'S HURT HER ARM. WE CONTINUED OUR FLT TO STL AND NOTIFIED ATC OF THE ENCOUNTER AND ASKED TO HAVE PARAMEDICS TO MEET ACFT AT THE GATE. FLT CONTINUED W/O INCIDENT. FLT ATTENDANT SUSTAINED A POSSIBLE WRIST INJURY. I HAVE NOT BEEN ABLE TO FIND OUT EXACT INJURY. THIS ENCOUNTER WAS UNAVOIDABLE SINCE WE WERE UNABLE TO DETECT IT ON RADAR. WE HAD DONE A VERY GOOD JOB OF NAV THROUGH THESE WX SYSTEMS. WE WERE ON OUR THIRD ARR CLRNC CHANGE TO GET TO STL. OUR DECISION TO GO S TO COL WAS A GOOD ONE SINCE IT PROVIDED A CLR AREA TO STL. THE ACFT WAS WRITTEN UP FOR SEVERE TURB ENCOUNTER, AND RECEIVED AN INSPECTION BY MECHS AT STL. NO DAMAGE TO ACFT. ACFT AND PLT CREW CONTINUED ON DUTY. COMPANY RPTS WERE SUBMITTED.

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.