The most successful of all SET designs was undoutably the SET 7. It started to take shape on the drawing boards in early 1930, as a two-seat biplane with a fixed undercarriage. Early models were built entirely of wood and covered with fabric, but later version had a metal fuselage. The first order came in December 1930, when 30 SET 7's were bought by the ARR for advanced training and liaison duties. By early 1932, the SET 7's had proven to be so useful that a second batch of 20 planes was ordered. All these airplanes were powered by a British Armstrong-Siddeley "Jaguar" IIIA radial engine rated at 365 HP.

In January 1934, the ARR requested that 20 improved observation and training aircraft, designated as SET 7K, be built. A more powerful engine was considered to be the plane's greatest need, so SET engineers chose the new IAR K7 as the new powerplant. This engine was the upgraded Romanian version of the French Gnome & Rhône 7Ksd radial engine, and it could produce 420 HP. Also, these planes were to be armed with a fixed forward-firing Vickers 7.7 mm machine gun and a twin rear-facing Lewis machine gun. Three more versions followed : SET 7KB, SET 7KD and the SET 7H.