Airworthiness Directives; Bombardier Model DHC-8-400 Series Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Bombardier Model DHC-8-400 series airplanes. That AD currently requires inspecting the electrical connectors of the fire bottles for the forward and aft baggage compartments and for the auxiliary power unit (APU) and engine nacelles to determine if they are connected correctly, and doing related investigative and corrective actions if necessary. This new AD adds a requirement to install/modify lanyards, mounts, and clamps to the forward and aft baggage compartment, APU, and engine nacelle fire extinguishing systems. This new AD also requires revising the aircraft maintenance manual to incorporate installation and removal procedures for certain fire bottles and fire extinguisher cartridges. This new AD also adds two airplanes to the applicability. This AD results from reports of the electrical connectors for the fire bottles in the forward and aft baggage compartments, APU, and engine nacelle being cross-connected. We are issuing this AD to detect and correct cross- connection of the fire bottles and to prevent cross-connection, which could result in failure of the fire bottles to discharge and consequent inability to extinguish a fire in the affected areas.