The flight from Taipei to about 300 nmi northwest of San Francisco was uneventful and the airplane was flying at about 41,000 feet mean sea level when the No. 4 engine lost power. During the attempt to recover and restore normal power on the No. 4 engine, the airplane rolled to the right, nosed over, and entered an uncontrollable descent. The captain was unable to restore the airplane to stable flight until it had descended to 9,500 feet. After the captain stabilized the airplane, he elected to divert to San Francisco International Airport, where a safe landing was made. Although the airplane suffered major structural damage during the upset, descent, and subsequent recovery, only two persons among the 274 passengers and crew on board were injured seriously. The maximum vertical acceleration forces recorded during the descent were 4.8Gs and 5.1Gs as the airplane descended through 30,552 feet and 19,083 feet, respectively. PROBABLE CAUSE: “The captain’s preoccupation with an inflight malfunction and his failure to monitor properly the airplane’s flight instruments which resulted in his losing control of the airplane. Contributing to the accident was the captain’s over-reliance on the autopilot after the loss of thrust on the no. 4 engine.”