Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Bombardier Model DHC-8-400 airplanes. That AD currently requires revising the Normal and Abnormal sections of the airplane flight manual (AFM) to include procedures that enable the flightcrew to determine if the main landing gear (MLG) is extended before landing, and to take appropriate actions if necessary. This new action would add an airplane to the applicability, and require replacing the existing MLG downlock proximity sensors with new, improved sensors. After the replacement, this action would also require removing from the AFM the revision to the Normal and Abnormal sections require by the existing AD. The actions specified by the proposed AD are intended to prevent failure of the MLG downlock proximity sensors on the same MLG at the same time, which could result in the MLG's failure to extend during landing, and cause injury to flightcrew and passengers.