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 testing of the spoiler electronic control unit (SECU) software for an upgrade, which revealed a timing error between the command and monitor channels. This AD requires revising the maintenance or inspection program to incorporate repetitive operational tests of the aileron disconnect system, and corrective action if necessary. This AD also requires modification and reidentification of the SECU, which would terminate the repetitive operational tests. We are issuing this AD to prevent a timing error in the SECU software, which, in combination with failure of the roll disconnect switch, could result in complete loss of spoiler functionality and consequent reduced controllability of the airplane.