The St Croix Excelsior (English: ever higher) is an American ultralight aircraft that was designed by Chad Wille and Charles Wille, produced by St Croix Aircraft of Corning, Iowa and first flown in 1980.
The aircraft was supplied in the form of plans for amateur construction with some hard-to-make parts available as well as partial kits.
[1][2][3][4] The Excelsior was designed to comply with the US FAR 103 Ultralight Vehicles rules, including the category's maximum empty weight of 254 lb (115 kg).
It features a strut-braced high-wing, a single-seat, open cockpit, tricycle landing gear and a single engine in pusher configuration.
The specified Zenoah G25 20 hp (15 kW) engine is mounted on top of the high wing and drives the tail-mounted propeller through a flexible extension shaft, that is designed to eliminate vibrations.