737 Rudder Enhancements
Existing Boeing 737 Rudder System
Principal changes affect the Power Control Unit (PCU) located in the airplane's tail; this unit controls the rudder's movement. The current PCU (the lower mechanism in this illustration) uses a single "dual concentric" valve to achieve redundancy -- an aerospace design principle in which duplicate systems are used to prevent overall failure if one part is damaged. It also relies on a single input arm to translate signals from the flight crew.
The 737 is among the world's safest airplanes, with a safety record twice as good as the overall jet fleet. This workhorse twinjet has completed more than 296 million hours of flight with an enviable record of reliability; today, a 737 takes off or lands somewhere in the world every 4.6 seconds.