A court-appointed psychiatrist said that a man charged with trying to hijack an Air Canada plane by holding an ax to the pilot's head is incompetent to stand trial. James Barrett Drake, 37, suffers from "auditory hallucinations" and "self-destructive tendencies" and is a recovering alcoholic, said Dr. Charles Noonan in a report disclosed at a magistrate's hearing. But Assistant U.S. Atty. Charles Burch said the prosecution still plans to seek a trial for Drake. Drake was arrested Nov. 6 after a three-hour standoff at San Francisco International Airport. Authorities said he entered the cockpit of a plane that was about to board 71 passengers for Toronto, grabbed a fire ax, held it to the pilot's head and demanded to be taken to London or another place of safety.