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SAI-Ambrosini SS.4 - Kingdom of Italy, 1939

Detailing the development and operational history of the SAI-Ambrosini SS.4 Canard-Configured Pusher Fighter Aircraft Prototype.

 Entry last updated on 5/31/2017; Authored by Staff Writer; Content ¬©

  SAI-Ambrosini SS.4  
Picture of SAI-Ambrosini SS.4
Picture of SAI-Ambrosini SS.4

SAI-Ambrosini produced the short-lived SS.4 canard fighter - the sole example lost in a crash on its second flight and claiming its pilot in the process.

Even before the American Curtiss XP-55 "Ascender" and the Japanese Kyushu J7W "Shinden" came into being as "canard" configuration fighter proposals of World War 2 (1939-1945), it was the Italian firm of SAI-Ambrosini that was making headway with their SS.4 development of 1939. Indeed the type became credited as being the first such aircraft to sport the "tail-first" arrangement and even the first to feature a retractable nose-wheel undercarriage. Designed around the concept of a single-seat, single-engine fighter, the SS.4 came to nothing when the program's sole prototype was lost in a crash.

The aircraft was the brainchild of Sergio Stefanutti who championed the canard form in previous aircraft of his own design. The new aircraft featured its wing mainplanes set aft of midships which repositioned the tailplanes forward along the sides of the nose - hence the "tail-first" descriptor used. The cockpit was situated slightly ahead of midships. As no true tail unit was used, the vertical tail fins were placed at the midway span of each wing mainplane, reaching beyond the trailing edges. A wholly retractable, wheeled undercarriage was featured and all-metal construction was used throughout the build of the SS.4.

Propulsion came from an Isotta-Fraschini Asso XI R.C.40 series V12 liquid-cooled inline piston engine developing 960 horsepower. The unique arrangement of the aircraft included the engine being set in the rear of the fuselage, aft of the cockpit, and thus a "pusher" arrangement was used in which the engine "pushed" instead of "pulled" the aircraft through the sky. The powerplant was mated to a variable pitch, three-bladed propeller unit. One recorded performance specification for the aircraft was a maximum speed of 355 miles per hour (another source states 335 miles per hour).

As a fighter development, proposed armament was 1 x 30mm cannon and 2 x 20mm cannons - all mounted in the nose as a lack of a forward-mounted engine allowed for the gun collection to be concentrated forward of the cockpit (as in the American Lockheed P-38 "Lightning" fighter) - giving unobstructed views when facing a target (and this no synchronizing gear was needed to fire through a spinning propeller blade).

First flight of the finalized prototype was on March 7th, 1939 - months before World War 2 would officially overtake the shaky peace in Europe. The aircraft was constructed by the workers at SAI-Ambrosini ("Societa Aeronautica Italiana Ing A Ambrosini"). A second flight followed the very next day but it was during this time aloft that the prototype and its pilot were claimed in a crash. The starboard aileron detached from the aircraft which produced an uncontrollable oscillation of that wing mainplane and forced the aircraft into an irrecoverable dive, leading to the crash of the prototype and the loss of the pilot's life (Ambrogio Colombo being at the controls). The crash occurred near the city of Campagna with the cause blamed on poor craftsmanship.

After this, no other work was had on the SS.4 or any similar product by the company. Its short time in the air and its origins in prewar Italy undoubtedly have led to this aircraft being consistently overlooked in terms of canard fighter aircraft developments of the war.

SAI-Ambrosini SS.4 Specifications

Service Year: 1939
Type: Canard-Configured Pusher Fighter Aircraft Prototype
National Origin: Kingdom of Italy
Manufacturer(s): Societa Aeronautica Italiana Ing A Ambrosini (SAI-Ambrosini) - Italy
Total Production: 1

Structural (Crew, Dimensions, Weights)

Operating Crew (Typical): 1
Overall Length: 22.15 feet (6.75 meters)
Overall Width: 40.42 feet (12.32 meters)
Overall Height: 8.20 feet (2.50 meters)

Weight (Empty): 3,968 lb (1,800 kg)
Weight (MTOW): 11,905 lb (5,400 kg)

Power / Performance (Engine Type, Top Speed)

Engine: 1 x Isotta-Fraschini Asso XI R.C.40 V12 liquid-cooled inline piston engine developing 960 horsepower.

Maximum Speed: 308 knots (354 mph; 570 kph)
Service Ceiling: 16,404 feet (5,000 meters; 3.11 miles)

Armament / Mission Payload

PROPOSED (never fitted)
1 x 30mm cannon in nose
2 x 30mm cannons in nose

Global Operators (Customers, Users)

Kingdom of Italy

Model Variants

SS.4 - Base Series Designation; sole prototype constructed.

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