A lightweight single seat fighter by Societa Aeronautica Italiana (Ambrosini), the Type 403 Dardo (Arrow) appeared in late 1942, developed from the S.A.I.207. The 403 differed by having a later series of 750 hp Isotta Fraschini Delta inverted V 12 aircooled engine, and constant speed Piaggio propeller. The airframe was of similar all-¬wood form but had a new wing profile, greater area, redesigned tail surfaces – the incidence of the tailplane being variable in flight – a redesigned rear fuselage, a fully-retractable tailwheel, provision for wing guns and a more robust structure.

The Stefanutti-designed S.403 flew for the first time in January 1943, powered by an Isotta-Fraschini R.C.21/60 engine of 750hp which provided a maximum speed of 403 m.p.h. In the final two years of the programme all that happened was the first few items of production tooling, but no Dardos.

The armament was two 20 mm (0.79 in) Mauser MG 151 cannon in the wings and two 12.7 mm (0.5in) Breda SAFAT heavy machine guns above the engine. The Dardo¬-C was to be a long range version with increased internal fuel and two drop tanks. An order for 3000 was placed with S.A.I. (800), Savoia Marchetti (1,200) and Caproni (1,000), but only the prototype flew as the Armistice ended all further work.

S.A.I.403
Engine: Isotta-Fraschini Delta HG 21/60, 559-kW (750-hp).
Take-off weight: 2640 kg / 5820 lb
Empty weight: 1983 kg / 4372 lb
Wingspan: 9.80 m / 32 ft 2 in
Length: 8.20 m / 26 ft 11 in
Height: 2.90 m / 9 ft 6 in
Wing area: 14.46 sq.m / 155.65 sq ft
Max. speed: 648 km/h / 403 mph
Range: 937 km / 582 miles
Ceiling: 10000 m
Crew: 1
Armament: two 20 mm (0.79 in) Mauser MG 151 cannon and two 12.7 mm (0.5in) Breda SAFAT machine guns

Developed from the S.107 lightweight single-seat fighter and featuring a similar wooden structure with monocoque fuselage, the S.207 was essentially a more powerful, productionised version of the basic design.
The first of two prototypes of the S.207 was flown in 1940, and was powered by an Isotta-Fraschini Delta R.C.35 12-cylinder inverted-Vee air-cooled engine rated at 705hp.

The second prototype was powered by the R.C.40 version of the engine rated at 750hp at 4000m. In dives the S.A.I.207 attained an indicated air speed of 466 m.p.h. at 10,000 ft. (representing a true air speed of 596 m.p.h., or Mach 0.86), and maximum level speed was 357 m.p.h., with the 750 h.p.

Armament was two synchronised 12.7mm machine guns, and a pre-series of 12 S.207s was built during March-July 1943, several of these being assigned to the 83a Squadriglia (18° Gruppo, 3° Stormo) for evaluation, and six being assigned in August 1943 to the 162a and 163a squadriglie (161° Gruppo).
The Ministero dell’Aeronautica placed orders for 2,000 of the S.A.I.207 production version, but only 13 pre-production aircraft were completed, the order then being switched to the improved S.A.I.403 Dardo (Dart).

One pre-series S.207 was fitted with an armament of two 20mm cannon.

Prototype
Engine: Isotta-Fraschini Delta R.C.35, 705hp

S.A.I.207
Engine: 1 x Isotta-Fraschini Delta HG 40, 559kW (750 hp).
Wingspan: 9m (29 ft 6.3 in)
Length: 8.02 m / 26 ft 4 in
Height: .40 m / 7 ft 10 in
Wing area: 13.90 sq.m / 149.62 sq ft
Empty weight: 1750 kg / 3858 lb
Max T/O weight: 2415 kg (5,324 lb).
Max speed: 398 mph at 14,765 ft
Operational range: 590 miles
Ceiling: 12000 m
Climb to 6000 m: 7 min 34 sec
Armament: 2 12,7 mm machine-guns
Max Dive speed: 960 km/h
Armament: 2 x 12.7-mm (0.5-in) mg.

Despite highly enthusiastic flight test reports, the need for increased production of combat aircraft necessitated the shelving of the S.A.I.7 trainer, but the aerodynamic qualities of the basic design were such that Stefanutti contemplated its adaptation as a lightweight interceptor fighter. The initial single-seat model, the S.A.I.I07, was built for research purposes and, powered by a 540-h.p. Isotta-Fraschini Gamma, was flown early in 1942

Working at the Societa Aeronautica Italiana of Ing Angelo Ambrosini, Sergio Stefanutti developed the S.107 lightweight fighter from the S.7 tandem two-seat aerobatic trainer and competition aircraft. Flown for the first time early in 1940, the S.107 was powered by a 515hp Isotta-Fraschini Gamma R.C.35-I 12-cylinder inverted-Vee air-cooled engine and armament was one 7.7mm machine gun. As initially flown, the S.107 was fitted with a long, faired windscreen extending over the engine in an attempt to reduce aerodynamic drag. This was found to impair vision from the cockpit, and it was replaced by a stepped windscreen. Performance was demonstrated at Guidonia, and progressive development of the basic design led to the S.207, the sole example of the S.107 being lost in an accident on 18 July 1941.

Engine: Isotta-Fraschini Gamma RC.35-I, 515 hp
Take-off weight: 1600 kg / 3527 lb
Empty weight: 1280 kg / 2822 lb
Wingspan: 9.00 m / 29 ft 6 in
Length: 8.00 m / 26 ft 3 in
Height: 2.40 m / 7 ft 10 in
Wing area: 13.10 sq.m / 141.01 sq ft
Max. speed: 500 km/h / 311 mph
Range: 800 km / 497 miles

Designed between October 1938 and April 1939 by Sergio Stefanutti as a two-seat high-speed tourer monoplane, the Ambrosini S.A.I.7 was a low-wing cantilever monoplane of wooden construction with fully retractable landing gear.
The first two aircraft were specifically intended to take part in the IV Avio Raduno del Littorio contest for touring aircraft, and they flew within days of each other, only shortly before the competition opened at Rimini aerodrome on 15 July 1939. Both aircraft had an additional streamlined glazed section added between the nose and the normal cabin enclosure for the contest. The S.A.I.7s did not win the contest, but one machine captured an international speed record over the 100km closed circuit on 27 August 1939. The F.A.I. Category I aircraft with a speed of 244 m.p.h
Ten of the S.A.I.7 militarised two-seat fighter trainer version appeared during 1943, and the experimental S.A.I.107, S.A.I.207 and S.A.I.403 light fighters were developed from it.
In 1949 S.A.I. Ambrosini placed the S.A.I.7 in full-scale production. The post-war version replaced the 209kW Hirth HM.508D engine of the record-breakers and the 209kW Isotta-Fraschini Beta RC.10 of the wartime version with an Alfa Romeo engine, but apart from improved constructional detail there were few major changes.
Most of the 145 post-war Ambrosini S.7s, some of them completed in single-seat configuration, formed the equipment of various flight training centres attached to the Aeronautica Militare zone headquarters. The military service was terminated in 1956
The S.7 participated in numerous competitions and Leonardo Bonzi established international records over the 100km and 1000km distances on 21 December 1951, with average speeds of 367.36km/h and 358.63km/h respectively.

Engine: Hirth HM.508D, 209kW (280-hp)

Engine: Isotta-Fraschini Beta RC.10, 209kW (280-hp)

Engine: 1 x Alfa Romeo 115ter, 168kW
Take-off weight: 1317 kg / 2904 lb
Empty weight: 1105 kg / 2436 lb
Wingspan: 8.79 m / 28 ft 10 in
Length: 8.17 m / 26 ft 10 in
Height: 2.8 m / 9 ft 2 in
Wing area: 12.8 sq.m / 137.78 sq ft
Max. speed: 358 km/h / 222 mph
Cruise speed: 264 km/h / 164 mph
Ceiling: 5250 m / 17200 ft
Range: 1000 km / 621 miles