The pilots of AirAsia Bhd. Flight 8501 cut power to a critical computer system that normally prevents planes from going out of control shortly before it plunged into the Java Sea, two people with knowledge of the investigation said. The action appears to have helped trigger the events of Dec. 28, when the Airbus Group NV A320 climbed so abruptly that it lost lift and it began falling with warnings blaring in the cockpit, the people said. All 162 aboard were killed. The pilots had been attempting to deal with alerts about the flight augmentation computers, which control the A320’s rudder and also automatically prevent it from going too slow. After initial attempts to address the alerts, the flight crew cut power to the entire system, which comprises two separate computers that back up each other, the people said.