Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9 series airplanes and C-9 (military) airplanes. This proposal would require either replacement or modification of the hydraulic damper assembly. This proposal is prompted by reports indicating that insufficient damping of the hydraulic shimmy damper in the main landing gear (MLG) can allow high torsional vibration to occur. The actions specified by the proposed AD are intended to prevent such vibration, which can damage the MLG assembly and lead to its collapse.