Private Pilot and Passenger Experience Wing Separation in Low Visibility (N9300A)

Incident Overview

A private pilot and a passenger were departing on a short flight to another airport. Weather conditions at the time included an overcast ceiling of approximately 600 feet and visibility of about half a mile. A witness who was a pilot examiner reported these conditions. Another witness stated that he was using his windshield wipers due to heavy mist.

Witness Observations

Ground witnesses reported hearing unusual sounds coming from an airplane within the overcast. They then observed the airplane spiraling out of the overcast with a wing missing. The pilot was not instrument rated. The incident occurred in a narrow valley, where some areas were reported to be in the clear.

Structural Examination

The left wing outboard panel separated at midspan, showing evidence of a positive or upward load. The left aileron was not located during the initial on-scene investigation but was recovered later. Metallurgical examination of the wing hinge fittings from the separated aileron revealed that there were existing cracks at the inboard lower aileron attachment point at the wing rear spar. The examination further revealed that the fittings had pulled out from the aileron spar during the wing overload.