Airworthiness Directives; McDonnell Douglas Model MD-90-30 Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain McDonnell Douglas Model MD-90-30 airplanes. This AD requires modifying the auxiliary hydraulic power system (including doing all applicable related investigative and corrective actions). This AD results from fuel system reviews conducted by the manufacturer, as well as reports of shorted wires in the right wheel well and evidence of arcing on the power cables of the auxiliary hydraulic pump. We are issuing this AD to prevent shorted wires or electrical arcing at the auxiliary hydraulic pump, which could result in a fire in the wheel well; and to reduce the potential of an ignition source adjacent to the fuel tanks, which, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.