The Superior Air Parts XP-400 is an aircraft engine, designed and produced by Superior Air Parts of Coppell, Texas, United States for use in homebuilt aircraft.
[1][2] The engine is not type certified and is therefore intended for homebuilt aircraft.
The company made this decision based on detonation problems found in some XP-400 engines that could not be resolved.
[4][5] In February 2020, Superior settled a lawsuit regarding the 2016 fatal crash of a Van's Aircraft RV-8A for US$5M.
In the accident investigation the NTSB determined that the crankshaft failed due to metal fatigue.