Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 777 airplanes. This proposed AD would require repetitive measurements of the freeplay of the right and left elevators, rudder, and rudder tab, and related investigative and corrective actions if necessary. This proposed AD would also require repetitive lubrications of the elevator, rudder, and rudder tab components. This proposed AD results from reports of freeplay-induced vibration of unbalanced control surfaces. Excessive freeplay of control surfaces can cause unacceptable airframe vibration during flight. 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 proposing this AD to prevent flutter, which can cause damage to the control surface structure and consequent loss of control of the airplane.