Airworthiness Directives; Bombardier Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Model CL-600-2B19 (Regional Jet Series 100 & 440) airplanes, that requires revising the airworthiness limitations section of the Instructions for Continued Airworthiness by incorporating new structural inspection intervals for the vertical beams of the pressure bulkheads at fuselage stations 409+128 and 559; repairing the vertical beams if necessary; and submitting inspection findings to the airplane manufacturer. This action is necessary to detect and correct, in a timely manner, fatigue cracks in the vertical beams of the pressure bulkheads at fuselage stations 409+128 and 559, which could result in the reduced structural integrity of the airplane. This action is intended to address the identified unsafe condition.