AD 2012-06-05 77 FR 16919

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 the inability to open the airstair door while on the ground, because the airstair door seal did not deflate, which prevented the airstair door from opening. This AD requires changing the wiring that controls the pneumatic shut-off valve. We are issuing this AD to prevent the airstair door seal from not deflating, which could result in the airstair door not opening and could impede evacuation in the event of an emergency.