What happened
The pilot was conducting a demonstration flight with a potential buyer when the aircraft experienced a significant structural failure. Immediately following takeoff, witnesses at the airport observed the right wing of the aircraft fold rearward. This caused the aircraft to enter an uncontrolled descent.
The investigation
Investigators determined that the forward lift strut on the right wing had separated from its attachment point at the lower fuselage clevis bolt. A metallurgical examination of the threaded barrel of the lift strut revealed significant damage. The bottom 1-1/4 inch of the barrel was missing most of its threaded crowns and was covered in corrosion residues. Additionally, the top 3/4 inch of the threads showed partial deterioration due to corrosion.
Further inspection of the hardware revealed that the entire length of the bolt hole was dry and lacked the linseed oil coating found on other struts, where the threaded holes remained wet. The aircraft had recently undergone a rebuild by A&E and A&I mechanics, and the annual inspection had been signed off just one day prior to the accident.