Backyard Flyer, 50 HP Hirth F23 engine, legal ultralight aircraft, Valley Engineering.

– Backyard Flyer, 50 HP Hirth F23 engine, part 103 legal ultralight aircraft. Dan Johnson talks to Alaina Lewis and Gene Smith from Culver Props about their 50 HP, Hirth F23 powered legal part 103 ultralight aircraft the Backyard Flyer during the .’s Airventure convention. The Backyard Flyer is usually powered by a four stroke, twin cylinder modified Generac engine. While it is a very fuel efficient and reliable engine it is also heavy. The Hirth F23 on the other