A loss of preload to the crankshaft gear attachment bolt, resulting in rotation of the crankshaft gear and a subsequent total loss of engine power. The root cause for the loss of preload could not be determined during a postaccident examination of the components.

The failure of the pilot-in-command to maintain airspeed following a reported loss of engine power, resulting in a stall/mush, uncontrolled descent, and in-flight collision with terrain. Factors in the accident were the pilot's intentional operation of the airplane with known deficiencies (inoperative No. 3 banner release), and inadequate installation of the banner tow-release hook assembly by company maintenance personnel.