Philippines President Corazon Aquino tripped on a wooden plank after stepping off her helicopter during a visit to the northern farming town of Cabiao Thursday, spraining her left ankle, a spokesman said. Her chief security officer prevented her from falling to the ground on her arrival, said press secretary Tomas Gomez. After her speech, Aquino's foot was bandaged aboard the helicopter and her schedule for the rest of the day was scrapped after her foot was X-rayed at the presidential palace clinic.