The pilot reported that during banner towing operations, he was on approach to drop the banner. He pulled the tow release, but the banner did not release. The banner hit the ground, broke away from the airplane, and the airplane nosed over.

The release mechanism has three hooks, but they typically only use the No. 1 hook. A postaccident examination of the hook release mechanism did not reveal any anomalies that would have prevented the banner from being released. The pilot believed that the ground crew mistakenly set-up hook No.3 to pick up and tow the banner instead of No. 1. Therefore, when he went to release the banner from hook No.1, there was nothing to release.

A postaccident examination of the airplane revealed substantial damage to the empennage.

The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.