HD 40

The Heinkel HD 40 was a special-purpose cargo aircraft developed in Germany in the 1920s to distribute the Berlin newspaper B.Z.. The success of Heinkel's previous design for the publisher, the HD 39, led to the order of a similar aircraft with greater capacity, and Heinkel responded with a machine of similar layout, but considerably enlarged. Like the HD 39, it was a conventional single-bay biplane with staggered wings of unequal span, and a fuselage that nearly filled the interplane gap. The pilot sat in an open cockpit, and the undercarriage was of fixed, tailskid type with divided main units. The wings were of wooden construction, while the fuselage was built from welded steel tube skinned in plywood.