Fokker S.IV

The Fokker S.IV was a two‑seat trainer biplane built by the Dutch manufacturer Fokker in the early 1920s. Developed to replace the earlier S.III, the S.IV first flew in 1921 and entered service with the Royal Dutch Air Force (Luchtvaartdienst) the following year. Its wooden frame was covered with fabric, and the aircraft employed a conventional sesquiplane layout with a single‑bay wing structure and staggered wings that gave good visibility for both instructor and pupil. Power was supplied by a 140 hp (104 kW) Le Rhône rotary engine, later replaced in some units by the more reliable 130 hp (97 kW) Hispano‑Suiza 8B. The S.IV featured a simple, open cockpit, fixed tailskid undercarriage, and a trainer‑oriented control system that allowed dual control inputs. Around 80 examples were produced, and the type saw extensive use not only in the Netherlands but also in the newly formed Indonesian Air Force and in several civil flight schools. Its reliability, straightforward handling, and relatively low operating cost made it an important stepping‑stone in pilot training during the interwar period, influencing later European trainer designs. The aircraft remained in service until the early 1930s, when it was gradually replaced by more modern monoplanes.