Unknown

The 'Unknown' was a pioneering experimental aircraft designed and built in 1912 by the German aviation enthusiast Oskar Ursinus, often called the “Father of the German Glider Movement.” Though only a single prototype was completed, the machine embodied Ursinus’s vision of a lightweight, high‑aspect‑ratio monoplane capable of both powered flight and unpowered soaring. Constructed with a wooden frame and covered in doped fabric, the wings spanned 13.5 metres and featured a patented flexible rib system that allowed the surface to twist subtly under load, reducing drag and improving lift‑to‑drag ratio. Power was supplied by a 60‑hp four‑stroke inline engine driving a two‑bladed propeller in a tractor configuration, while the cockpit was enclosed in a streamlined nacelle with removable side panels for glider training. The aircraft’s first flight on 23 June 1912 demonstrated a maximum speed of 115 km/h, a climb to 1,500 metres in six minutes, and a record‑setting glide ratio of 1:12, unmatched among contemporary designs. Though the program was halted by the outbreak of World War I, the ‘Unknown’ influenced later German high‑performance gliders and laid the groundwork for the post‑war sailplane renaissance, cementing Ursinus’s legacy as a catalyst for modern aeronautical engineering.

Oskar Ursinus

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Design & Classification