Airworthiness Directives; Dornier Model 328-300 Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to all AvCraft Dornier Model 328-300 airplanes. That AD currently requires modifying the electrical wiring of the fuel pumps; installing insulation at the flow control and shut-off valves, and other components of the environmental control system; installing markings at fuel wiring harnesses; replacing the wiring harness of the auxiliary fuel system with a new wiring harness; and installing insulated couplings in the fuel system; as applicable. The existing AD also requires revising the Airworthiness Limitations section of the Instructions for Continued Airworthiness to incorporate new inspections of the fuel tank system. This new AD replaces the flight-hour-based threshold for conducting certain initial inspections, with a calendar- based threshold. This AD results from fuel system reviews conducted by the manufacturer. 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.