There are two losses of aircraft(United 585 near Colorado Springs (737-200) and USAir 427 near Pittsburgh (737-300)) which have not been fully explained. However most experts believe that both
crashes, which claimed the life of 157 people, as well as the Eastwind and MetroJet incidents were caused by uncommanded rudder troubles due to failures in the PCU and/or yaw dumper system. Apart from that there have been hundreds of incidents where pilots reported uncommanded swings of the rudder in the 737's long carrer. All the early models had no system to limit a possible uncommanded rudder movement. Unfortunately Boeing and the FAA have been very slow and reluctant to act. This is understandable, but not acceptable and could lead to more incidents. Just imagine the millions of pounds it would cost Boeing to acknowledge that the rudder is defective and the associated changes to almost 3000 in-service aircraft. However, Boeing at least introduced some changes to new-build versions of the 737,which of course do not affect all the previous models. Don't get me wrong: I don't think the 737 is an unsafe aircraft (I just flew on one three weeks ago), but in the interest of flight safety it would be better to fully investigate the causes of this rudder phenomenon.