What happened
While climbing between 14,000 feet and 16,000 feet in light icing conditions, the flight crew of the aircraft experienced a moderate shudder. This was immediately followed by the autopilot disconnecting and a 15-degree roll to the left. The crew declared an emergency and diverted the flight, which landed without further incident. All occupants were not injured.
The investigation
Post-landing inspections identified that a section of the left wing de-icing boot had delaminated. Testing showed that applying pressure to the system created a bubble; when the pressure was released, the delaminated plies remained stretched beyond their elastic limits, resulting in wrinkles.
Investigators found no evidence of contamination within the plies. The separation was located between the knit fabric and the adhesion coat. While the outer delaminated plies were unusually durable—causing a large bubble to form rather than a typical burst—the manufacturer noted that this failure mode is consistent with an elastomeric construction that had reached the end of its useful life.