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Ambrosini SS.4

The SAI-Ambrosini SS.4 was an Italian fighter prototype developed in the late 1930s, featuring a canard-style wing layout and a pusher propeller.

Development of the SS.4 was abandoned after the prototype crashed on its second flight.

The SS.4 was a single-seat fighter of all metal construction with a canard configuration wing with twin fins mounted on the wing trailing edges, retractable tricycle undercarriage and short fuselage with rear-mounted engine driving a pusher propeller.

The pilot was accommodated in an enclosed cockpit in the centre of the fuselage forward of the two fuel tanks and aft of the armament in the nose.

Visibility from the cockpit was excellent to the sides and front, but restricted to the rear by the large main wing, engine and large twin fins positioned at approximately the half span position.

Flying controls consisted of elevators on the trailing edges of the canard fore-plane controlling pitch, rudders on the large fins controlling yaw and ailerons on the main wings to control roll.

Pitch trim was set by adjusting a trim tab on the starboard elevator.

The moderately swept, tapered, high aspect ratio wings had no sweep on the trailing edge and a cut back to give clearance for the propeller, with the large fins with rudders extending past the trailing edge at the ends of the cut-backs, to ensure enough moment to give adequate control and stability.

The delta fore-plane was of low aspect ratio with the elevators sited below the trailing edge similar to the method used by contemporary Junkers aircraft like the Junkers Ju 87.

The engine was a powerful liquid-cooled Isotta-Fraschini Asso XI R.C.40 engine capable of 960 hp (720 kW) driving a three bladed metal propeller.

The engine was cooled by two radiators either side of the fuselage in ducts just behind the cockpit.

Fuel for the engine was housed in two fuel tanks located mid-fuselage along with an oil tank.

Armament was to be two 20 mm (0.787 in) cannon and one 30 mm (1.181 in) cannon, clustered in the nose.





6.74 m (22 ft 1 in)


12.32 m (40 ft 5 in)


2.49 m (8 ft 2 in)

Wing area

17.5 m2 (188 sq ft)

Gross weight

2,449 kg (5,400 lb)


1 × Isotta-Fraschini Asso XI R.C.40, V-12 liquid-cooled piston engine,

720 kW (960 hp)


3-bladed metal pusher propeller


Maximum speed

571 km/h (355 mph, 308 kn)

Stall speed

110 km/h (68 mph, 59 kn)



2 × 20 mm cannon


1 × 30 mm cannon (mounted in nose)


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