Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all McDonnell Douglas Model DC-9- 10, -20, -30, and -40, and C-9 (military) series airplanes. This proposal would require modifying the piping of the potable water system. This proposal is prompted by reports of ice forming on the control cables in the wheel well of the left main landing gear due to the freezing and rupturing of undrained potable water pipes. The actions specified by the proposed AD are intended to prevent such ice formation, which could render the slat, aileron, and spoiler flight controls inoperative, and consequently could result in reduced controllability of the airplane.