Incident Description
The flight crew reported that as the airplane was climbing between 14,000 and 16,000 feet in light icing conditions, they experienced a moderate shudder. The autopilot disconnected, and the airplane immediately rolled 15 degrees to the left. The crew declared an emergency and diverted the flight. No further incidents occurred during the diversion.
Examination Findings
After landing, examination of the aircraft revealed that a section of the left wing de-icing boot had delaminated. When pressure was applied to the de-icing system, a bubble formed at the delaminated area. When pressure was released, the delaminated plies were stretched beyond their elastic limits and did not return to their normal shape, resulting in wrinkles. Analysis of the plies found no evidence of contamination. The separation occurred between the adhesion coat and the knit fabric.
Manufacturer's Report
The manufacturer of the de-icing boot reported that this mode of failure was consistent with an elastomeric construction that had reached the end of its useful life. The outer delaminated plies were found to be unusually durable, which led to the formation of a large bubble instead of the normally expected burst of the outer plies.