The SAI SS.4 project was created in 1939 as a result of an attempt to build an airplane according to the "duck" scheme. Work on the aircraft was started by engineer Stafannuti at SAI's Guidonia Experimental Center. The first experimental aircraft designated SS.2, powered by a Keller 16CV engine, was ready in 1936. Tests of the aircraft were successful, and in 1937 one of the two SS.2s was equipped with a more powerful CNA 38 Cv engine, this aircraft received the designation SS.3 and its own name "Anitra" (translated from Italian - "duck").
On the basis of the aerodynamic scheme worked out during the creation of SS.3, a heavier aircraft of the "duck" scheme - SS.4 with an Isotta Fraschini Asso XI Rc-40 engine with a capacity of 960 hp was created. from. According to its purpose, it was a fighter plane with retractable tricycle landing gear and powerful small arms and cannon armament, consisting of one 30-mm cannon and two 20-mm cannons. The plane took off for the first time on March 7, 1939, showing the highest (of the two "ducks") flight performance. After successfully passing through two years of intense testing, it crashed due to engine failure.
The horizontal tail of the aircraft consisted of a fixed stabilizer and traditional elevators. The problem of a small shoulder of the vertical tail and rudders was solved by using a two-fin vertical tail on the aircraft (the keels are located in the middle of the span of each of the small swept wing consoles). A similar aerodynamic layout was subsequently used on some aircraft of the "duck" and "tailless" schemes.
Wartime conditions did not allow for a full cycle of flight design tests, so the second prototype SS.4 was not finally built, and the company focused its efforts on improving aircraft of traditional schemes.
|Wing area, m²
|1 × PE Isotta Fraschini Asso XI Rc-40, power, hp
|Maximum speed, km/h
|Cruising speed, km/h
|Rate of climb, m/min
|Service range, km
|Service ceiling, m
| One 30mm and two 20mm cannons