Airworthiness Directives; Bombardier, Inc. Airplanes

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model BD-100-1A10 (Challenger 300) airplanes. This AD was prompted by multiple reports of a short circuit between the heater element and the metal sheath of the pitot-static probe heater. This AD requires replacement of the left and right pitot-static probes with newly redesigned left and right pitot-static probes. We are issuing this AD to prevent degradation of the heating ability of the pitot- static probe heater, resulting in erroneous airspeed indication during flight in icing conditions and consequent reduced controllability of the airplane.