LOSS OF ACFT CTL OCCURS WHEN A B747-400 RUNS INTO SEVERE TURB AT FL310; 250 KTS; 60 NM NW OF DVV; CO.

Narrative

AT FL350; 20 MINS E OF ROCKIES; INBOUND TO FQF VOR; CTR RPTED POCKETS OF MODERATE TURB. ADVISED HEAD FLT ATTENDANT TO SECURE GALLEYS AND CARTS AND STRAP IN AND MADE PA TO CABIN ANTICIPATING TURB FOR EVERYONE TO REMAIN SEATED WITH SEATBELT FASTENED; CABIN SVC WAS DISCONTINUED AND FLT ATTENDANTS WOULD ALSO BE SEATED. QUERIED CTR FOR RIDE RPTS LOWER AND THEN ASKED FOR FL310 BETTER RIDE AND 4000 FT BELOW OPTIMUM ALT. CTR TURNED US N 30 DEGS FOR DSCNT. UPON REACHING FL310; CLRED US DIRECT TO MEEKER AND TOLD US TO SLOW TO 250 KTS. JUST AFTER SLOWING TO 250 KTS; WE HEARD ANOTHER ACR RPT NEAR SEVERE TURB. CTR CAME BACK WITH A WARNING THAT IT WAS RIGHT AHEAD OF US. IN JUST A FEW SECONDS WE ENCOUNTERED IT AND AIRSPD IMMEDIATELY DECAYED TO 230 KTS. I FIREWALLED THE PWR AND HAD MY FO TELL HIM WE WERE ACCELERATING TO 290 KTS (TURB PENETRATION SPD). ACFT ROLLED 15 DEGS AND WE WERE AT TIMES LIGHT IN OUR SEATS. FO TURNED ON CONTINUOUS IGNITION. TURB LASTED ABOUT 45 SECONDS. WE GOT OUT OF IT AND I MADE A PA TO THE CABIN THAT I THOUGHT WE WERE OUT OF IT; BUT TO STAY SEATED. CTR SAID RIDE AHEAD SMOOTH AND IT WAS. UNTIL TECHNOLOGY IMPROVES FOR FORECASTING; LITTLE CAN BE DONE. WHAT TO DO IS WRITTEN IN OUR HANDBOOKS AND WE TRAIN FOR IT IN THE SIMULATOR. NO FURTHER RECOMMENDATIONS. SUPPLEMENTAL INFO FROM ACN 540114: THE CAPT WENT FIREWALL PWR AS I BUGGED 290 KIAS AND TURNED ON CONTINUOUS IGNITION.