AD FAA-2017-0805

We are adopting a new airworthiness directive (AD) for all The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), and DC-9-87 (MD-87) airplanes, Model MD-88 airplanes, and Model MD-90- 30 airplanes. This AD was prompted by a report of loss of airspeed indication due to icing. This AD requires modifying the air data heat (ADH) system. We are issuing this AD to address the unsafe condition on these products.