In the time that aviation industry was rapid developed, there were many special-designed aircraft. This barrel-like aircraft, was designed by Luigi Stipa, an Italian aeronautical engineer.
In the 1920s, Stipa applied his study of hydraulic engineering to develop a theory of how to make aircraft more efficient as they traveled through the air.
According to his theory, Bernoulli's principle could be applied to airflow to make engine more efficient by directing its propeller wash through a Venturi tube in a design he termed an "intubed propeller".
Eventually, he published his ideas in the Italian aviation journal "Rivista Aeronautica", then asked the Air Ministry to build a prototype aircraft to prove his concept.
References: Wikipedia, History.net
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