Airworthiness Directives; McDonnell Douglas Model DC-8 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Model DC-8 series airplanes, that requires, among other things, repetitive leak tests of the lavatory drain systems and repair, if necessary; installation of a lever lock cap, vacuum breaker check valve, or flush/fill line ball valve on the flush/fill line; periodic seal changes; and replacement of "donut" type waste drain valves installed in the waste drain system. This amendment is prompted by continuing reports of damage to engines, airframes, and property on the ground, caused by "blue ice" that forms from leaking lavatory drain systems on transport category airplanes and subsequently dislodges from the airplane fuselage. The actions specified by this AD are intended to prevent such damage associated with the problems of "blue ice."