Tupolev I-4

The Tupolev I‑4 was a Soviet single‑seat fighter prototype developed in the early 1920s at the Central Aerohydrodynamic Institute (TsAGI) under the direction of Andrei Tupolev. Conceived as a successor to the earlier I‑1 and I‑2 designs, the I‑4 first flew in 1923 and incorporated several aerodynamic advances derived from wind‑tunnel experiments at TsAGI. The aircraft featured a wooden fuselage with a metal‑skinned wing, a conventional biplane layout, and a 300 hp Hispano‑Suiza 8Fb V‑8 engine driving a two‑bladed propeller. Its wings were staggered and of unequal span, giving the machine a relatively high aspect ratio and improved lift‑to‑drag ratio for its era. The I‑4 employed a fully enclosed cockpit canopy, a novelty for Soviet fighters, and was equipped with synchronized forward‑firing machine guns.

Although only a handful of prototypes were built and the type did not enter mass production, the I‑4 proved essential in validating TsAGI’s aerodynamic data and in training Soviet designers in modern construction techniques. Lessons learned from the I‑4 directly influenced later Tupolev fighters such as the TB‑1 bomber and the Polikarpov I‑16, marking the aircraft as a pivotal step in the evolution of Soviet aeronautical engineering.

Central Aerohydrodynamic Institute

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Production & History

Design & Classification