New flight-control systems known as "fly-by-wire" in commercial jets can lead to a rare but potentially dangerous type of problem, according to a report released last month by a National Research Council committee that included a UC Davis engineer. The plane may begin to move up and down or roll right or left in a severe wave-like pattern, making it impossible for the pilot to control the aircraft with the precision needed. More targeted aircraft testing and simulation should be conducted to uncover such design problems, and pilots and other personnel involved in aircraft design and operation need more training to prevent and prepare for these situations, the committee recommended. "We'd like to be able to bring together manufacturers and researchers to identify the problems early -- ideally in the simulator before the plane is built, but if not then in the flight testing," says Ron Hess, a UC Davis professor of mechanical and aeronautical engineering who served on the NRC committee. Developed in military planes and now becoming common in commercial jets, fly-by-wire systems replace much of the mechanical devices like pulleys and cables that connect the cockpit controls to the airplane control surfaces like a rudder or wingflap.