AD FAA-2011-1089

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model BD-100-1A10 (Challenger 300) airplanes. This AD was prompted by reports of deformation found at the neck of the pressure regulator body on the oxygen cylinder and regulator assembly (CRA). This AD requires an inspection to determine if a certain oxygen CRA is installed and the replacement of affected oxygen CRAs. We are issuing this AD to prevent elongation of the pressure regulator neck, which could result in rupture of the oxygen cylinder, and, in the case of cabin depressurization, oxygen not being available when required.