ANDRIA HALL, CNN ANCHOR: The Federal Aviation Administration may recommend redesigning the rudder control system of the Boeing 737. CNN's Jonathan Aiken reports on tests that found the system could fail in unexpected though improbable ways.</s>JONATHAN AIKEN, CNN CORRESPONDENT (voice-over): A panel of engineers was surprised to discover that ice could build up inside the 737's rudder system, which could cause pilots to lose control of the plane.</s>TIM MCSWEENY, FAA: It is possible that you might get some kind of a moisture buildup. What we showed in the laboratory, we have yet to determine can it actually occur in real-life situations in the air.</s>AIKEN: The rudder system of the 737 is one of the most investigated pieces of machinery ever, ever since the 1991 crash of a United 737 in Colorado that killed 25 people and a US Air Flight in 1994 near Pittsburgh in which 132 people died. Probes of these crashes focused on internal valves in the rudder system that have since been redesigned. And over the years, Boeing has made other modifications in the later models of the 737. This latest study, involving engineers both inside and outside the aviation industry, has been the most thorough yet, and the FAA says it sees nothing to warrant wholesale changes to the jet. The 737 is the work horse of civil aviation with a takeoff somewhere in the world, on average, once every five seconds.</s>MCSWEENY: We've got an airplane that has been studied and studied and studied. And the present study is so thorough, I mean, it's without precedent. And yet the answer is there is nothing in the design of that rudder that would cause us to take any immediate safety action.</s>AIKEN (on camera): FAA officials stress the information coming from this evaluation team is preliminary. The board should wrap its work and submit a report by June. Detailed scientific analysis and specific safety recommendations come much later. Jonathan Aiken for CNN, Washington.
Study Examines Safety of 737 Jet