Caudron R.4

The Caudron R.4 was a French two‑seat biplane reconnaissance and fighter aircraft developed during the final year of World War I. Designed by the Caudron brothers, it first flew in March 1916 and entered service with the Aéronautique Militaire in 1917. The R.4 was built in large numbers—over 1,000 airframes were produced at the company's Le Bœuf plant—making it one of the most numerous French types of the conflict.

The aircraft featured a conventional unequal‑span biplane wing arrangement with a wooden frame, fabric covering, and a fixed tailskid undercarriage. Power came from a 220 hp Renault 12F V‑12 engine, delivering a top speed of roughly 190 km/h and a service ceiling of 5,800 m. Its dual‑seat layout allowed a pilot and an observer/gunner, the latter operating a flexible Lewis gun mounted on a ring. Some R.4s were fitted with a forward‑firing Vickers gun, enabling limited air‑to‑air combat.

Although originally intended for observation, the R.4’s robust construction and relatively high performance led to its adaptation as a light fighter and trainer in the post‑war years. Its widespread use helped standardise French aerial tactics and contributed to the development of later Caudron designs such as the C.460 series, cementing its place in early aviation history.