Summary
We propose to adopt 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), DC-9-87 (MD-87) airplanes, Model MD-88 airplanes, and Model MD-90- 30 airplanes. This proposed AD was prompted by a report of loss of airspeed indication due to icing. This proposed AD would require modifying the air data heat (ADH) system. We are proposing this AD to address the unsafe condition on these products.