Flight Sequence
The pilot was making a second attempt to pick up a banner. The aircraft approached the two banner poles and catch rope at a low altitude. Prior to flying between the poles, engine sounds were heard to increase. When the aircraft flew over the catch rope, another increase in engine sounds was heard, and the aircraft flew upward. After the last increase in engine sounds, the engine sounds decreased, followed by two surges of the engine. The aircraft then descended to the ground in an approximate 45-degree nose-down attitude and struck the ground. Prior to contacting the ground, one last surge of the engine was heard.
Post-Accident Examination
Examination of the wreckage revealed that the altimeter, tachometer, and vertical speed indicators were not connected to their respective hoses and cables. The knurled fitting that attached the tachometer cable to the tachometer was found unscrewed, and the threads were undamaged. Examination of the engine revealed no mechanical deficiencies. The fuel tanks contained fuel that was absent of debris, and no obstructions were found in the fuel system.
Conditions
The carburetor heat handle was found in the off position. An icing probability chart indicated that the conditions were conducive for serious icing in cruise flight.