Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all McDonnell Douglas Model DC-9- 32 series airplanes modified per Supplemental Type Certificate SA4371NM. This proposal would require an inspection to determine if certain ground wires on the water heater of each lavatory are installed, and corrective action, if necessary. This action is necessary to detect improper grounding of a water heater, which, coupled with an internal short in the water heater, could result in heat or smoke damage or a fire on the airplane. This action is intended to address the identified unsafe condition.