Heinkel He 64

The Heinkel He 64 was a German sports biplane from the 1930s designed for flying competitions and speed trials. The aircraft was ready in 1932 and successfully participated in the Europa Rundflug, and the following year it took part in the International Touring Contest. It was equipped with a folding wing with a single trapezoidal spar with slots; it was the first wing of its kind. The automated slots allowed the aircraft to fly at steep angles of climb and relatively low landing speeds. Source: Wikipedia