On April 27, 2006, at 1425 eastern daylight time, a Beech C90A, N90CH, registered to Chartco, LLC, and operated by Carolina Air Charter, Inc., as a 14 CFR Part 91 corporate flight, encountered a windshield deicing mechanism fire in the cockpit while in cruise flight from Concord, North Carolina, to Washington Dulles International Airport, Dulles, Virginia. Instrument meteorological conditions prevailed, and an instrument flight rules flight plan was filed. The pilot and the two passengers reported no injuries, and the airplane received minor damage. The flight originated from the Concord Regional Airport, Concord, North Carolina on April 27, 2006, at 1331. According to the pilot, while in cruise flight at 17,000 feet, he smelled smoke. He stated that, a few seconds later, flames and smoke started shooting out of the lower left windshield. The pilot stated he believed it was the windshield heat unit, so he turned off the windshield heat, and the flames went out, but the smoke persisted. The pilot declared an emergency with air traffic controllers and diverted to Raleigh-Durham International Airport in Raleigh, North Carolina. The airplane landed safely, and the pilot and passengers deplaned on the tarmac. Examination of the airplane found scorch marks and soot on the left windshield near the terminal block. The damaged windshield was shipped to PPG Industries, Inc., for further examination. Examination revealed the unit showed a condition similar to other units that were found to have overheated blocks during late 1996 and early 1997. These blocks were subject to a joint investigation by Raytheon Aircraft Company and PPG during 1997. That investigation identified the root cause of the terminal block overheating, relating to the manufacturing process. The manufacturing process was corrected by PPG in August 1996. Raytheon issued Safety Communiqué No. 134, describing the events, part numbers affected, and procedures to perform in case of such an event. These procedures were added to the FAA-approved airplane operating handbook in June 1997. The damaged windshield from this incident was one of the windshields manufactured just prior to the correction of the manufacturer process.