Akaflieg Berlin A.B.4

The Akaflieg Berlin A.B.4, designed and built in the early 1930s by the student group of the Technische Universität Berlin under the direction of Martin Schrenk, represents a pivotal step in German sport‑glider development. Initiated in 1932 as a response to the rapidly evolving aeronautical curricula, the A.B.4 combined academic research with practical construction, embodying the collaborative spirit of the Akaflieg movement. Its all‑wood monocoque fuselage featured smooth plywood skin and a cantilever high‑wing layout, while an innovative single‑spar wing employed a combination of spruce ribs and fabric covering to achieve a low drag coefficient. The aircraft’s 12‑meter wingspan and modest glide ratio of 22:1 made it competitive in contemporary contests, and its lightweight design enabled pilots to explore thermalling techniques that would later influence powered aircraft performance. Though only a handful were produced before the outbreak of World War II curtailed civilian projects, the A.B.4’s emphasis on structural efficiency and pilot feedback contributed to subsequent German glider designs such as the DFS Rhönlerche. Today, the A.B.4 is remembered as a testament to university‑driven innovation and the formative role of Martin Schrenk in advancing pre‑war aviation engineering.

Martin Schrenk

Akaflieg Berlin A.B.4

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Design & Classification