AD NUMBER: 2006-07-23
SUBJECT: Airworthiness Directive 2006-07-23
FAA is adopting a new airworthiness directive (AD) for all Boeing
Model 757 airplanes. This AD requires repetitive measurements of
the free play of each of the three power control units (PCUs) that
move the rudder; repetitive lubrication of rudder components; and
corrective actions if necessary. This AD results from a report of
free play-induced vibration of the rudder. The potential for
vibration of the control surface should be avoided because the
point of transition from vibration to divergent flutter is unknown.
We are issuing this AD to prevent excessive vibration of the
airframe during flight, which could result in divergent flutter and
loss of control of the airplane.