NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The banner towing airplane was being positioned to another airport. After takeoff, the airplane engine lost power. Unsuitable terrain limited the pilot's options, and he struck a chain link fence during a forced landing. Examination revealed low compression in the engine, with air bypass on all exhaust valves, and evidence of detonation. The airplane had 3 fuel tanks, each of which held 18 gallons, and two of which contained uncontaminated fuel. One tank contained fuel to which Marvel Mystery Oil had been added. The fuel was pink in color and had an oily feel. The FAA reported that they found an empty can of Marvel Mystery Oil in the operator's trash. The recommended ratio for the additive to fuel was 1 part additive to 100 parts fuel. The operator did not have any specific instructions on how or when to add the Marvel Mystery Oil, or what ratio to use. The pilot, chief pilot, and manager all denied adding the substance to the fuel. In addition, the manager reported that he interviewed the maintenance personnel and they denied adding the Marvel Mystery Oil to the fuel.