BANNER TOW OPNS WERE BEING CONDUCTED. THE PLT TOOK OFF TO MAKE THE 1ST BANNER TOW OF THE DAY. WHEN THE TOW HOOK (GRAPPLING HOOK ON A ROPE) WAS DEPLOYED, THE TOW LINE BCM ENTANGLED IN THE RUDDER CTL & INTERFERED WITH ITS MOVEMENT. ACCORDING TO OPERATOR PSNL, THE PLT SHOULD HAVE VISUALLY CHECKED THE GRAPPLING HOOK LINE AFTER IT WAS DEPLOYED TO ASSURE THAT IT WAS NOT FOULED ON THE RUDDER BELL CRANK; AND IF IT WAS, HE SHOULD HAVE LNDD TO FREE THE LINE, RATHER THAN PICK UP THE BANNER. THE ACFT WAS EQUIPPED WITH A HOOK RELEASE MECHANISM (IAW STC SA 1-349). HOWEVER, THERE WAS EVIDENCE THAT WHEN THE BANNER WAS CAPTURED, ITS WT PLACED TENSION ON THE TOW HOOK LINE & PRECLUDED ITS RLS AS WELL AS CAUSING A DEFLECTED RUDDER. SUBSEQUENTLY, THE ACFT STALLED & SPUN TO THE GND. OPERATOR PSNL RPRTD THAT THE ACFT WOULD HAVE BEEN CONTROLLABLE WITH THE LINE FOULED ON THE RUDDER BELL CRANK. FAA CIRCULAR (AC 43.13-2A) STATED THAT THE SYS SHOULD HAVE BEEN TESTED TO INSURE THERE WAS NO INTERFERENCE WITH THE TAILWHEEL OR ADJACENT STRUCTURE.