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

We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires modifying the auxiliary hydraulic power system (including doing all applicable related investigative and corrective actions). This new AD requires these same actions, using corrected service information. This AD was prompted by fuel system reviews conducted by the manufacturer, as well as reports of electrically shorted wires in the right wheel well and evidence of arcing on the auxiliary hydraulic pump power cables, which are routed within the tire burst area. We are issuing this AD to prevent electrically shorted wires or arcing at the auxiliary hydraulic pump power cables, which could result in a fire in the wheel well. We are also issuing this AD 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.