Airworthiness Directives; McDonnell Douglas Model DC-9, DC-9-80, and C-9 (Military) Series Airplanes, and Model MD-88 Airplanes

This amendment supersedes an existing airworthiness directive (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 requires an inspection to detect chafing on the FIREX pipe assembly of the number one engine; and either repair of chafed pipe assemblies or replacement of the chafed pipe assemblies with new pipe assemblies; and modification of the FIREX and the pneumatic sense pipe assembly clamp marriage. This amendment revises the applicability of the existing AD to include additional airplanes and remove others. This amendment is prompted by reports of incidents in which the pneumatic sense pipe chafed against the FIREX supply pipe of the number one engine. The actions specified by this AD are intended to prevent chafing of the FIREX supply pipe, which could result in a hole in the pipe and consequently prevent the proper distribution of the fire extinguishing agent within the nacelle in the event of a fire.