A set of contra-rotating propellers has eight blades (four blades on the front propeller and four blades on the back propeller) that are 50 feet in diameter, which dwarfs the GE90 turbofan, is at least about two and a half times the size of the propellers on the aforementioned turboprop and propfan engines, and is noticeably bigger than the largest marine ship propellers, although it is less than half as wide as the main rotors on the largest helicopters.