The BDP S-1 (Boyevoi Desantnyi Planer – troops assault glider) was a military glider of the Soviet Union. It was produced by the Bureau of Special Construction (Osoboe Konstruktorskoe Buro) in 1941 as a glider infantry troop transport. It accommodated 20 troops plus one pilot, and had gun ports for defense. Of wooden construction, the glider featured a high aspect ratio, high-cantilever wing and trailing flaps, utilizing a wheeled-carriage for takeoff and landing on plywood runners [1][2] Due to the advance of German forces, only seven were built until the factory was moved, and production was shifted to powered aircraft.[3]