What happened
While performing a domestic IFR cross-country flight, the aircraft experienced a slight vibration as it climbed through FL310 toward an assigned altitude of FL390. During this climb, a passenger seated on the left side of the aircraft noticed portions of the skin on a non-structural wing panel on the left wing peeling off and separating from the wing structure. The passenger alerted a crewmember to the condition.
The flight crew subsequently performed a precautionary landing, which was completed without further incident. No injuries were reported among the occupants.
The investigation
Post-flight examination of the aircraft identified that a section measuring 48 inches wide by 31 inches long had separated from the trailing edge of the fixed trailing edge upper panel on the left wing. Additionally, investigators found that a three-inch portion of the trailing edge on the left fore flap panel had also sustained damage and separated from the airplane.
Maintenance personnel contracted by the operator determined that the delamination of the honeycomb panel was caused by water contamination.