Airworthiness Directives; Bombardier, Inc. Airplanes

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc., Model DHC-8-102, -103, and -106 airplanes; and DHC-8- 200 and DHC-8-300 series airplanes. This AD was prompted by a report of a beta warning horn (BWH) system failing to activate when the beta mode was triggered. This AD requires modifying the BWH microswitch installation. We are issuing this AD to prevent the inadvertent activation of ground beta mode during flight, which could lead to engine overspeed, engine damage or failure, and consequent reduced controllability of the airplane.