Summary
This document proposes the supersedure of two existing airworthiness directives (AD), applicable to certain McDonnell Douglas Model DC-9, DC-9-80, and C-9 (military) series airplanes, and Model MD- 88 airplanes, that currently require installation of hydraulic line restrictors in the main landing gear (MLG), and modification or replacement of the left and right MLG hydraulic damper assemblies. This action would require an additional modification of the MLG hydraulic damper assemblies, or replacement of the MLG hydraulic damper assemblies with modified and reidentified hydraulic damper assemblies. This proposal is prompted by reports indicating that MLG hydraulic damper assemblies removed for overhaul had failed or damaged spring retainers, due to insufficient material thickness of the spring retainers. The actions specified by the proposed AD are intended to prevent failure of the hydraulic damper assemblies of the MLG, which could result in vibration damage and collapse of the MLG.