Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Bombardier Model DHC-8-400 series airplanes. This proposal would require two actions--a modification and a replacement--affecting the fuel tanks in the wings. All affected airplanes would require modification of the clearance of the fuel tank vent lines to the left and the right wing fuel tanks. Some affected airplanes would also require replacement of three existing fuel probes from the center fuel tank on the left and right wings with new production fuel probes. This action is prompted by mandatory continuing airworthiness information from a foreign airworthiness authority. This action is necessary to prevent inadequate clearance between the fuel tank vent lines and the adjacent rib structures of the wings or failure of certain temporary, reworked fuel probes in the center fuel tanks in the wings. Either condition could compromise the airplane's lightning protection system, possibly resulting in a fire or explosion if the airplane were hit by lightning. This action is intended to address the identified unsafe condition.