Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Model MD-90-30 airplanes. The existing AD currently requires modifying the auxiliary hydraulic power system (including doing all applicable related investigative and corrective actions). This proposed AD would require these same actions, using corrected service information. This proposed AD results from 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 proposing 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 proposing 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.