Primary finding
Probable cause
The windshield failed due to arcing from an inadequate solder connection at the anti-ice power terminal block.
Investigator assessment
Analysis narrative
The arcing/overheating of the braid wire caused the fire event in the cockpit. Removal of the terminal block and sealant revealed an arcing hot spot where the failure occurred at power braid wire position A. There was no visible solder at the connection point of braid wire A, which led to the arcing of the power braid wire and the fire event in the cockpit.
Source record
Factual narrative
The damaged left side windshield (P/N NP139321-17 S/N 18338H6714) from N561NN was removed from the airplane and shipped to PPG Aerospace in Huntsville, Alabama. PPG examined the window in November 2020. The windshield serial number indicated that the windshield was a new unit and was completed in December of 2018. The subject windshield was installed on N561NN and had accumulated 3238.53 flight hours and 2870 flight cycles. PPG Aerospace completed manufacture of the window in December 2018. A teardown of the unit identified the failure origin underneath the power terminal block at the power braid A location. Removal of the terminal block and sealant revealed an arcing hot spot where the failure occurred at power braid wire position A. There was no visible solder at the connection point of braid wire A. The braid wire solder connection point at position B was still intact.