What happened
During the process of picking up a banner, the tow rope became wrapped around the release hook. As a result, the pilot was unable to release the banner at the conclusion of the flight.
Upon landing, the aircraft encountered a right crosswind while the banner remained attached. As the aircraft slowed, the pilot lost directional control, causing the airplane to depart the runway to the left side and ultimately nose over. There were no injuries reported in the incident.
The investigation
The investigation examined the configuration of the banner attachment point, which consisted of a hook on the end of a rod attached to the main landing gear. This placement was located forward of the aircraft's center of gravity, making directional control extremely difficult or impossible as the plane decelerated.
Interviews with an FAA inspector revealed that rope is more prone to twisting around a release hook compared to metal cables. The investigation also noted that while both rope and cable are common in banner towing, tow hitches mounted on the tailwheel are considered safer than those mounted on the main landing gear.