Accident Overview
A training flight for banner towing operations ended with the airplane coming to rest inverted after a hard landing. The pilot-in-command (PIC) was seated in the rear seat, providing instruction to the front seat pilot who was being trained on banner towing procedures.
Sequence of Events
The flight conducted tow training, after which the banner was dropped. The pilots entered the traffic pattern for landing. On final approach, the front seat pilot was manipulating the controls with the flaps fully extended. The flight encountered gusty wind conditions. After touchdown, a gust of wind caused the airplane to become airborne again. The front seat pilot reported applying only partial power, and the airplane subsequently landed hard.
Examination and Findings
The hard landing resulted in the separation of the right main landing gear wheel/axle assembly. The airplane then nosed over and came to rest in an inverted position. Examination of the threads on all four axle attach nuts revealed that they were stripped.