Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 757 airplanes. This proposed AD would require repetitive measurements of the freeplay of each of the three power control units (PCUs) that move the rudder; repetitive lubrication of rudder components; and corrective actions if necessary. This proposed AD results from a report of freeplay-induced vibration of the rudder. We are proposing this AD to prevent excessive vibration of the airframe during flight, which could result in divergent flutter and loss of control of the airplane.