Created Wednesday, Jun 30th 2021 14:24Z, last updated Saturday, May 28th 2022 19:33Z
A PSA Airlines Canadair CRJ-700, registration N709PS performing flight
AA-5440 from Akron,OH to Philadelphia,PA (USA), was climbing out of Akron's runway 23 when the captain noticed a glow around the right windshield terminal block, which subsequently started to emit sparks and a two-inch flame. The captain shut the windshield heating down which immediately stopped the sparks and flame. The crew declared emergency, stopped the climb at about 3500 feet and returned to Akron for a safe landing on runway 23 about 20 minutes after departure.
On Jun 30th 2021 the NTSB reported an inflight fire causing minor damage occurred. The occurrence was rated an incident and is being investigated by the NTSB.
On May 28th 2022 the NTSB released their final report concluding the probable cause of the incident was:
Moisture ingression thru the window humpseal coming into contact with the terminal block braid wires.
The NTSB analysed:
The outboard glass ply failed due to a fracture along the bottom aft edge of the window caused by an electrical arcing event. The arcing event was caused by moisture ingression that came into contact with the window heating terminal block braid wires.
An evaluation of the fracture pattern indicated that the outboard glass ply failed due to a fracture along the bottom aft edge of the window.
The conductive film interlayer located under the outboard ply reached a high enough temperature during the arcing event that it melted and fractured the outboard glass ply of the window. The arc escaped via the glass fracture, allowing the arc to come into contact with and melt the humpseal sealant. There were no indications of any burning or fire events on the inboard surface of the window (including the power terminal block).
The event was contained to the outboard glass ply. The power terminal block was removed, and no damage was noted to the wiring and solder connections.
There was evidence of moisture ingress and degradation of the interlayer of window was noted in some areas around the periphery of window. Humpseal degradation and improper humpseal repair techniques were noted.
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