Apr. 13, Santa Barbara, Calif. / Boeing 737-300

At 19:15 PDT, a United Airlines Boeing 737-300 experienced an uncommanded roll to the left during level cruise at flight level 310, 25 miles northwest of Santa Barbara. The returned to Los Angeles International Airport. The unexpected roll was described as a rudder kick, a sharp quick uncommanded kick to the left. The autopilot was on during the 20- to 30-degree roll excursion to the left.