Airworthiness Directives; Bombardier, Inc. Airplanes

We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400 series airplanes. This AD was prompted by a report of a translating door handle jamming during opening of an aft door. This AD requires replacing the handle shaft with a new single-piece machined handle shaft on the aft entry and service doors, and requires revising the maintenance program by incorporating a new airworthiness limitation task. We are issuing this AD to prevent a migrated pin from jamming a translating door handle, which could prevent opening of the door and impede an emergency evacuation.