AD FAA-2011-1229

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model DC-9-10, DC-9-20, DC-9-30, DC-9-40, and DC-9- 50 series airplanes; and Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9- 83 (MD-83), DC-9-87 (MD-87), MD-88, and MD-90-30 airplanes; equipped with center wing fuel tank and Boeing original equipment manufacturer- installed auxiliary fuel tanks. This AD was prompted by fuel system reviews conducted by the manufacturer. This AD requires adding design features to detect electrical faults and to detect a pump running in an empty fuel tank. We are issuing this AD to reduce the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.