AD FAA-2008-0413

We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. This AD requires replacing the pushrods for the left and right elevator tab control mechanisms with new, improved pushrods. This AD results from a report of a rod end fracture on a rudder power control unit (PCU) control rod, which is similar to the ones used for the elevator tab pushrods. Analysis revealed that the fractured rod end had an incorrect hardness, which had probably occurred during the manufacture of the control rod. We are issuing this AD to prevent fracture of the elevator tab pushrod ends, which could result in excessive in-flight vibrations of the elevator tab, possible loss of the elevator tab, and consequent loss of controllability of the airplane.