Incident Description
While in cruise flight at an altitude of 17,000 feet, the pilot detected the smell of smoke. Within seconds, flames and smoke began emanating from the lower left windshield. The pilot deactivated the windshield heat system, which extinguished the flames, though smoke persisted. An emergency was declared with air traffic controllers, and the pilot diverted to a nearby airport, landing the airplane without further incident.
Examination Findings
Post-landing inspection of the aircraft revealed scorch marks and soot on the left windshield in the vicinity of the terminal block. The damaged windshield was sent to manufacturer PPG Industries, Inc., for detailed analysis.
Investigation and Corrective Actions
Examination by PPG indicated that the unit exhibited a condition comparable to other windshields that had experienced overheating of the terminal blocks during late 1996 and early 1997. These earlier incidents had prompted a joint investigation by Raytheon Aircraft Company and PPG in 1997. That investigation identified the root cause of the terminal block overheating as related to the manufacturing process. PPG had corrected the manufacturing process in August 1996. In response, Raytheon issued Safety Communiqué No. 134, which outlined the events, affected part numbers, and recommended procedures. These procedures were subsequently incorporated into the FAA-approved airplane operating handbook in June 1997. The windshield involved in this incident was determined to have been manufactured shortly before the manufacturing process correction was implemented.