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.

Ambrosini SS.4
Class Aircraft
Type Fighter
Manufacturer SAI Ambrosini
Production Period 1939 - 1939
Origin Italy
Country Name Origin Year
Italy 1939
ManufacturerName Production From Production To Quantity
SAI Ambrosini 1939 1939 1 View

Sergio Stefanutti had already experimented with canard aircraft with the S.C.A. SS.2 and S.C.A. SS.3 Anitra ("Duck"), light aircraft built by Stabilimento Costruzioni Aeronautiche (SCA) at Guidonia (a new city focused on aviation). The single-seat SS.2 had a canard wing configuration, fixed undercarriage and was powered with a 2-cylinder Keller engine rated at 16 hp (11.93 kW). The SS.2 first flew in 1935, and one of the two prototypes was converted into a two-seater with a larger 38 hp (28.34 kW) CNA II engine built by Compagnia Nazionale Aeronautica. This new aircraft first took to the air on 2 October 1937 and was officially revealed in Milan at an international air exposition and the small fixed-undercarriage SS.2 was sent to Passignano for evaluation. Experience with this machine and the study of its aerodynamics led Stefanutti to design a canard style interceptor and air superiority fighter, designated SS.4, very similar in layout to the SS.2 and SS.3.

The SS.3 had a span of 12.77 m (41.9 ft) and was 6.00 m (19.7 ft) long with an overall height of 2.01 m (6.6 ft). With a 16 hp (12 kW) engine it was capable of a maximum speed of 87 mph (140 km/h) and able to reach an altitude of 13,120 ft (4,000 m) altitude. Stalling speed was 34 mph (55 km/h):

A prototype SS.4 was built at the Società Aeronautica Italiana - Ambrosini factory in Passignano sul Trasimeno, Umbria. Relatively little flying was carried out as development of the SS.4 was abandoned after the prototype crashed, killing the test pilot. The design barely compared favourably to contemporary fighters, and the Regia Aeronautica decided not to pursue the design, despite having already ordered a second aircraft which was cancelled.

The prototype SS.4 was built by SAI Ambrosini, Passignano sul Trasimeno, and then sent to Eleuteri airport, Castiglione del Lago, also in the Trasimeno area. There, the aircraft was successfully flown for the first time on 7 March 1939. The next day the SS.4 prototype was scheduled to be transported to Aviano airbase by rail, but Ambrosini's chief test pilot Ambrogio Colombo wanted a second test flight. After 45 minutes, an aileron malfunctioned just 2 km (1.2 mi) from Eleuteri. Colombo attempted to land but was unable to reach the runway and crashed near Campagna, hitting a tree. Colombo was killed when the engine pushed through the rear bulkhead and crushed him against the front of the cockpit. A memorial to him was erected near the site of the crash. The investigation into the crash concluded that the accident was due to imperfect construction which led to a faulty installation of the aileron which had failed. The study also pointed out the excessive vibrations transmitted by the engine to the wing.

Role Fighter
Manufacturer SAI-Ambrosini
Designer Sergio Stefanutti
First flight 7 March 1939
Number built 1

General characteristics

  • Crew: 1
  • Length: 6.74 m (22 ft 1 in)
  • Wingspan: 12.32 m (40 ft 5 in)
  • Height: 2.49 m (8 ft 2 in)
  • Wing area: 17.5 m2 (188 sq ft)
  • Gross weight: 2,449 kg (5,400 lb)
  • Powerplant: 1 × Isotta-Fraschini Asso XI R.C.40 V-12 liquid-cooled piston engine, 720 kW (960 hp)
  • Propellers: 3-bladed metal pusher propeller


  • Maximum speed: 571 km/h; 308 kn (355 mph)
  • Stall speed: 110 km/h (68 mph; 59 kn)

End notes