Airworthiness Directives; McDonnell Douglas Model DC-9-14, DC-9-15, DC-9-15F, DC-9-31, DC-9-32, DC-9-32 (VC-9C), DC-9-32F, DC-9-32F (C-9A, C-9B), DC-9-33F, DC-9-34, and DC-9-34F Airplanes; and Model DC-9-21, DC-9-41, and DC-9-51 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-9 series airplanes, that currently requires replacing the transformer ballast assembly in the pilot's console with a new, improved ballast assembly. This amendment expands the applicability of the existing AD to include additional airplanes and provides an optional method for accomplishing the requirements of the existing AD. The actions specified by this AD are intended to prevent overheating of the ballast transformers due to aging fluorescent tubes that cause a higher power demand on the ballast transformers, which could result in smoke in the cockpit. This action is intended to address the identified unsafe condition.