Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) series airplanes, Model MD-88 airplanes, and Model MD-90-30 series airplanes. This proposal would require installation of a pipe support and clamps on the hydraulic lines in the aft fuselage; replacement of the hydraulic pipe assembly in the aft fuselage with a new pipe assembly; and installation of drain tube assemblies and diverter assemblies in the area of the auxiliary power unit (APU) inlet; as applicable. This proposal is prompted by reports of smoke and odor in the passenger cabin and cockpit due to hydraulic fluid leaking into the APU inlet, and subsequently, into the air conditioning system. The actions specified by the proposed AD are intended to prevent such hydraulic fluid leakage due to fatigue vibration and cracking in the flared radius of a hydraulic pipe in the aft fuselage, which could result in smoke and odors in the passenger cabin or cockpit.