A federal appellate court has reversed one of two counts of which an Army private was convicted after he piloted a light plane over then-President Ronald Reagan's Santa Barbara ranch. A three-judge panel of the U.S. 9th Circuit Court of Appeals ruled that Ralph Myers, 34, was simply guarding against self-incrimination when he lied to Secret Service agents about why he flew over the ranch the night of Aug. 13, 1987. They let stand, however, Myers' conviction for earlier telling precisely the same lie to Federal Aviation Administration officials because the investigation had not yet reached the stage of being an obvious criminal inquiry. Assistant U.S. Atty. George Newhouse said it is unlikely that Myers will be retried on the overturned count. In any event, he said, Myers has finished serving his sentence.