On June 16, 2021, about 0730 central daylight time, an experimental, amateur-built RV-10 airplane, N878TD, was substantially damaged when it was involved in an accident near Fort Worth, Texas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot departed Hicks Airfield (T67), Fort Worth, Texas, about 0700 and headed northwest before returning to T67. The pilot reported that, during the initial climb following a touch-and-go landing, the engine backfired and lost power about 200 ft above ground level (agl). As the airplane descended, it collided with a power line before impact with terrain and a tree. The pilot added that the engine continued to run before the impact but did not develop enough power to maintain altitude. The airplane sustained damage to the landing gear, engine, and substantial damage to the fuselage during the accident. Examination of the airplane revealed that the engine was equipped with an electronic ignition system, (labeled as #1 and #2) and automotive-style sparkplugs. The sparkplugs and valve covers were removed from each cylinder and the engine rotated by hand. Continuity through the valve train to the accessory section was noted. The bottom set of sparkplugs appeared wet and black in color. (See Figure 1.) Figure 1: Bottom set of sparkplugs The ignition system was field tested by passing a magnet over the flywheel ignition sensor; spark was only observed on one bank of the ignition system. The ignition leads and coil labels did not necessarily correspond to the associated cylinder. The ignition firing order was not confirmed. The ignition control boxes were located behind the firewall, and the fuselage was cut open to allow access to the boxes. The output cable on ignition box #1 was found disconnected. (see Figure 2.) Figure 2: Output cable as found on ignition box #1 The pin connectors were fully secured. Additionally, as mounted, access to the boxes were limited and could only be done from under the instrument panel and by reaching above the rudder pedals.