Amateur-built CASSUTT M 11 N55XJ accident near Castroville, California

Probable cause

A failure of the outboard trailing edge rib in the left wing, which resulted in a separation of the left aileron and a loss of control.

NTSB analysis

The pilot was performing an aileron roll when the airplane suddenly entered an uncommanded high-g maneuver, and he lost control of the airplane. He was able to release his seat belt and parachute to the ground. The left wing and aileron separated from the airplane before impacting a muddy field.

The mostly intact left aileron, attached torque tube, and both trailing edge ribs separated from the wing and the torque tube fractured from the bellcrank in the fuselage. The forward halves of the upper and lower flanges and the forward flange of the outboard trailing edge rib were separated cleanly from the wing consistent with an adhesive type failure at the interface between the carbon and adhesive. The aft halves of the upper and lower flanges of the outboard trailing edge rib were separated from the trailing edge skins with a cohesive type failure through the adhesive. The lower flange also had evidence of foam core material in the bond line.

The available evidence suggests that the outboard trailing edge rib failed along the bond lines between the rib, rear spar, and trailing edge skins, which resulted in a loss of control when the left aileron separated from the wing and the left wing separated from the airplane.

Text from the NTSB. Open the NTSB docket for WPR23LA128 for the full record.