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
In an aircraft with a pusher configuration (as opposed to a tractor configuration), the propeller(s) are mounted behind their respective engine(s). Since a pusher propeller is mounted behind the engine, the drive shaft is in compression in nor ...
. Development of the SS.4 was abandoned after the prototype crashed on its second flight.
Development
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'' at
Guidonia (a new city focused on aviation). The single-seat SS.2 had a canard wing configuration and fixed undercarriage, and was powered with a two-cylinder Keller engine rated at . The SS.2 first flew in 1935, and one of the two prototypes was converted into a two-seater with a larger CNA II engine built by ''
Compagnia Nazionale Aeronautica __NOTOC__
Compagnia Nazionale Aeronautica was a manufacturer of aircraft and aircraft engines established in Italy in 1920 by Count Giovanni Bonmartini. Together with a group of World War I veteran pilots, he operated a flying school in Rome from a ...
''. This new aircraft first took to the air on 2 October 1937, and was officially revealed in
Milan
Milan ( , , Lombard: ; it, Milano ) is a city in northern Italy, capital of Lombardy, and the second-most populous city proper in Italy after Rome. The city proper has a population of about 1.4 million, while its metropolitan city h ...
at an international air exposition; the small fixed-undercarriage SS.2 was sent to
Passignano sul Trasimeno
Passignano sul Trasimeno is a ''comune'' (municipality) in the Province of Perugia in the Italian region of Umbria, located about 20 km northwest of Perugia.
Passignano was home to a historic Italian airplane factory, the SAI Ambrosini, now ...
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 , and was long, with an overall height of . With a engine, it was capable of a maximum speed of and able to reach an altitude of . Stalling speed was :
A prototype SS.4 was built at the
''Società Aeronautica Italiana - Ambrosini'' factory in
Passignano sul Trasimeno
Passignano sul Trasimeno is a ''comune'' (municipality) in the Province of Perugia in the Italian region of Umbria, located about 20 km northwest of Perugia.
Passignano was home to a historic Italian airplane factory, the SAI Ambrosini, now ...
,
Umbria
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. The first flight took place on 7 March 1939, but in its second flight next day, the aircraft crashed, killing Ambrosini's chief test pilot Ambrogio Colombo. A second prototype was ordered, but development priority was placed on more easily developed wooden aircraft, and the SS.4 design was abandoned in 1942.
Design
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 a 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 roughly 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 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 cannon and one cannon, clustered in the nose.
Operational history
![Colombomemorial](https://upload.wikimedia.org/wikipedia/commons/e/e9/Colombomemorial.jpg)
The prototype SS.4 was built by SAI Ambrosini,
Passignano sul Trasimeno
Passignano sul Trasimeno is a ''comune'' (municipality) in the Province of Perugia in the Italian region of Umbria, located about 20 km northwest of Perugia.
Passignano was home to a historic Italian airplane factory, the SAI Ambrosini, now ...
, and then sent to Eleuteri airport,
Castiglione del Lago
Castiglione del Lago is a town in the province of Perugia of Umbria (central Italy), on the southwest corner of Lake Trasimeno. Orvieto is south, Chiusi is to the south west, Arezzo is to the north west, Cortona is to the north and Perugi ...
, 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 Aviano ( fur, Davian; cim, Pleif) is a town and ''comune'' in the province of Pordenone at the foot of the Dolomites mountain range in Friuli-Venezia Giulia, northern Italy.
Aviano is home to the C.R.O. (Oncological Referral Center), a cancer rese ...
airbase by rail, but Ambrosini's chief test pilot, Ambrogio Colombo, wanted a second test flight. After 45 minutes, an
aileron malfunctioned just from Eleuteri. Colombo attempted to land, but was unable to reach the runway and crashed near
Campagna
Campagna (Italian: ) is a small town and ''comune'' of the province of Salerno, in the Campania region of Southern Italy. Its population is 17,148. Its old Latin name was Civitas Campaniae (City of Campagna). Campagna is located in one of the ...
, 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 Colombo 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 that had failed. The study also pointed out the excessive vibrations transmitted by the engine to the wing.
Specifications (SS.4)
See also
References
{{DEFAULTSORT:Ambrosini Ss.4
SAI Ambrosini aircraft
1930s Italian fighter aircraft
Single-engined pusher aircraft
Aircraft first flown in 1939