Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for all Model 747SP series airplanes. This AD was prompted by a report of a rudder hard-over event on a Model 747-400 series airplane, caused by a rudder power control module (PCM) manifold cracking and separating in the area of the yaw damper cavity end-cap. This condition could result in a hard-over of the rudder surface leading to an increase in pilot workload and a possible high-speed runway excursion upon landing, in the event of failure of the lower or upper rudder PCM manifold. This AD requires replacing or modifying the upper and lower rudder PCMs. We are issuing this AD to correct the unsafe condition on these products.