Incident Narrative
While climbing through 17,000 feet, the captain detected a smell of smoke. Moments later, flames and smoke began emanating from the lower left windshield. The captain suspected the windshield heat unit as the source. The first officer deactivated the windshield heat, causing the flames to cease, though smoke persisted. The captain declared an emergency with air traffic control and returned to Asheville Regional Airport.
Examination Findings
A post-incident examination of the windshield revealed that overheat damage resulted from an improperly installed fastener. This fastener caused arcing between the terminal block lug, the aircraft wiring eyelet, and the fastener and lock washer that secure the components together. Over time, the arcing degraded the solder junction connecting the terminal block to the windshield heating system braid wire. This degradation led to heat damage to the sealant and subsequently produced the flame.
Probable Cause
Improper installation of a fastener, resulting in arcing between electrical components, degradation of the solder junction, and subsequent overheating and fire in the windshield heat system.