The Earthstar Thunder Gull is a family of cantilever high-wing, tricycle gear ultralight aircraft, manufactured by Earthstar Aircraft of Santa Margarita, California as a kit for amateur construction or as a completed aircraft.
Earthstar Thunder Gull
Gull 2000 on skis
Thunder Gull Odyssey
Thunder Gull Odyssey showing the unusual staggered side-by-side seating arrangement
The Rotax 503 is a 37 kW (50 hp), inline 2-cylinder, two-stroke aircraft engine, built by BRP-Rotax GmbH & Co. KG of Austria for use in ultralight aircraft.
Rotax 503
A Rotax 503 mounted on a Flightstar II ultralight
The prototype Blue Yonder Twin Engine EZ Flyer is powered by two 503s in pusher configuration
Air Creation Racer ultralight trike with Rotax 503 mounted up-right. Below the muffler is the smaller after-muffler.