HISTORY OF FLIGHTOn August 5, 2014, about 1020 Pacific daylight time, an experimental, David Thompson, Challenger II, N518DT, collided with terrain during a forced landing following a loss of engine power near Winterhaven, California. The private pilot and one passenger sustained serious injuries; the airplane sustained substantial damage to the fuselage. The owner/pilot was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The cross-country personal flight departed Yuma, Arizona, about 0940, with a planned destination of El Cajon, California. Visual meteorological conditions prevailed, and no flight plan had been filed.

The pilot reported that after refueling at Yuma International Airport (YUM) they departed and climbed to 6,500 feet when the engine suddenly quit. The pilot attempted to restart the engine but was unsuccessful. During the landing and while still 20 ft high, the airplane encountered a wind gust, impacted the ground hard, and nosed over. TESTS AND RESEARCHThe airplane structure was substantially damaged during the accident sequence, but the engine appeared to be undamaged. The airplane electrical system appeared to be intact, however during the prestart sequence, the number two electrical system would not activate properly. The number one system indicated an ignition fault, which investigators were unable to correct.

Several attempts to start the engine were unsuccessful; the engine would stumble, backfire, and stop. Investigators examined the sparkplugs and determined that only one set of the plugs were firing on each cylinder. The engine was flooding out and when the engine would start to run the exhaust was black in color. The Computer Engine Control (CEC) module did not contain nonvolatile memory, and it could not be determined if the CEC was functioning properly.