Incident Overview
A banner tow operation was in progress when the pilot took off to perform the first tow of the day. After deploying the tow hook—a grappling hook attached to a rope—the tow line became entangled in the rudder control system, interfering with its movement. According to operator personnel, the pilot should have visually inspected the grappling hook line after deployment to ensure it was not fouled on the rudder bell crank. Had he observed such fouling, he should have landed to free the line rather than proceeding to pick up the banner.
Aircraft Equipment and Events
The aircraft was equipped with a hook release mechanism in accordance with Supplemental Type Certificate (STC) SA 1-349. However, evidence indicated that when the banner was captured, the weight of the banner placed tension on the tow hook line. This tension precluded the release of the line and caused a deflected rudder. Subsequently, the aircraft stalled and spun to the ground.
Operator Statements and Regulatory Guidance
Operator personnel reported that the aircraft would have remained controllable even with the line fouled on the rudder bell crank. Federal Aviation Administration Advisory Circular (AC) 43.13-2A states that the system should have been tested to ensure there was no interference with the tailwheel or adjacent structure.