The Savoia-Marchetti SM.79 Sparviero (Italian for sparrowhawk) is a three-engined medium bomber developed and manufactured by the Italian aviation company Savoia-Marchetti. It may be the best-known Italian aeroplane of the Second World War. The SM.79 was easily recognizable due to its fuselage's distinctive dorsal "hump", and was reportedly well liked by its crews. It was nicknamed il gobbo maledetto ("damned hunchback")."Savoia-Marchetti SM.79." Aviation History On-Line Museum. Retrieved: 26 December 2011.
The SM.79 was developed in the early 1930s. It is a cantilever low-wing monoplane of combined wood and metal construction, designed with the intention of producing a swift eight-passenger transport aircraft capable of outperforming the fastest of its contemporaries, but its potential as a combat aircraft quickly attracted the attention of the Italian government. It made its first flight on 28 September 1934 and early examples of the type established 26 separate world records between 1937 and 1939, qualifying it for some time as the fastest medium bomber in the world.Arena et al. 1994, p. 7. As such, the SM.79 quickly came to be regarded as an item of national prestige in Fascist Italy, attracting significant government support and often being deployed as an element of state propaganda. Early on, the aircraft was routinely entered in competitive fly-offs and air races, seeking to capitalise on its advantages, and often emerged victorious in such contests.
The SM.79 first saw combat during the Spanish Civil War. In this theatre it normally operated without fighter escort, relying on its high speed to evade interception. The SM.79's performance during the Spanish deployment was successful and stimulated demand for the type, including a decision to adopt it as the backbone of Italy's bomber units. Both Yugoslavia and Romania opted to procure the type for their own air services, while large numbers were also procured for the Regia Aeronautica. Almost 600 SM.79-I and –II aircraft were in service when Italy entered the Second World War in May 1940; thereafter, they were deployed in every theatre of war in which the Italians fought.
The SM.79 was operated in various capacities during the Second World War, initially being used mainly as a transport aircraft and medium bomber.Angelucci and Matricardi 1978, p. 198. Following pioneering work by the "Special Aerotorpedoes Unit", Italy put the type to work as a torpedo bomber; in this role, the SM.79 achieved notable successes against Allied shipping in the Mediterranean theatre of the war.Arena et al. 1994, p. 9. A specialised drone version of the aircraft flown by remote control was also developed, although the Armistice with Italy was enacted prior to any operational deployment. It was the most numerous Italian bomber of the Second World War, with about 1,300 built. The type would remain in Italian service until 1952.Mondey 1996, p. 236.
Development
Savoia-Marchetti started work on what would become the SM.79 in 1934. The design team was headed by aeronautical engineer Alessandro Marchetti. It was originally conceived of as a fast transport aircraft, capable of accommodating up to eight passengers and also capable of being used in air races (such as the MacRobertson Air Race). The design, which was initially designated as the SM.79P (P stood for passenger), was once intended to be a civil derivative of the Savoia-Marchetti SM.81, a militarised transport/bomber aircraft that was itself based upon the Savoia-Marchetti S.73 airliner.Apostolo 1967, p. 3.
The company quickly set about the construction of a single prototype, being keen to participate in the high-profile MacRobertson race if possible. The SM.79 had a three-engine configuration (two in mid-wing positions and the third mounted on the nose) due to commercial safety concerns rather than for speed.Apostolo 1967, pp. 3, 10. Originally, there were plans to use the Isotta-Fraschini Asso XI Ri ; however, it was decided to revert to the less powerful Piaggio Stella P.IX R.C.40, a derivative of the license-produced version of the British Bristol Jupiter, on which many of Piaggio's engines were based.Sgarlato 2002, p. 4.
The prototype made its maiden flight on 28 September 1934, piloted by Adriano Bacula. Despite the company's ambitions, the prototype (registration I-MAGO) was not completed in time for it to take part in the London-Melbourne race. The prototype quickly demonstrated its speed, making a flight from Milan to Rome in just one hour and 10 minutes, flying at an average speed of . On 20 July 1935 it was given its Certificate of Airworthiness. Soon after, on 2 August 1935, the prototype established a new speed record by flying from Rome to Massaua, in Italian Eritrea, in 12 flying hours (with a refuelling stop at Cairo, Egypt).Sgarlato 2002, p. 5.
Various other world records were established by the prototype. It was determined early on that it was the engines, rather than the airframe itself, which were its limiting factor; accordingly, the prototype was re-engined multiple times. During 1935, the P.IX engines which had been originally installed were replaced by Alfa Romeo 125 RC.35s, a license-produced version of the Bristol Pegasus; during 1936 these were replaced by Alfa Romeo 126 RC.34s. The high performance demonstrated by the prototype attracted the attention of the Italian military, which approached Savoia-Marchetti with a request to investigate the prospects for producing a bomber version of the type.
An evaluation of the suitability of the SM.79 for military use concluded that the installation of either two or three defensive machine guns would produce a highly effective defense against contemporary fighter aircraft. In response to the military interest, the company decided to construct a militarised second prototype. While it did not differ in structure from the first civil-orientated prototype, it had a faired ventral nacelle for a bomb-aimer, a forward-firing machine gun above the pilot's cabin, and another machine gun located on the underside of the tail. A third machine gun could be installed at an open position aft of the dorsal fairing .Apostolo 1967, pp. 3–4.
During October 1936, production of the SM.79 started. Initially, priority was given to producing civil aircraft while military variants continued to be developed; as such, there were a pair of principal commercial variants produced as well, these being the speed-focused SM.79C (C standing for race) and the long-range SM.79T (T for Transatlantic).Apostolo 1967, pp. 4–5. Aircraft amongst these variants participated in various early record-setting attempts during 1937 and 1938.Apostolo 1967, pp. 5–7. In light of opinions amongst prospective export customers regarding the desirability of a nose-mounted gun position (impossible due to the nose-mounted third engine), Savoia-Marchetti started work on the design of a two-engined model of the type, known as the SM.79B. This had a redesigned nose section which incorporated the bomb-aimer's position and an elevated position for the pilot, along with a single movable machine gun, and was first flown during 1936.Apostolo 1967, p. 10.
In addition to those manufactured by Savoia-Marchetti, in order to meet demand Aeronautica Umbra, based in Foligno, also produced the type. Manufacture continued until June 1943, during which time a total of 1,217 aircraft were completed, many of which were completed to bomber, torpedo-bomber, and transport configurations.Matricardi, Paolo. Aerei Militari: Bombardieri e Transporti. Milano: Mondadori Electa Editori, 2006. The SM.79 has been described as being by far the most important Italian offensive warplane of the Second World War, and one of the very few Italian aircraft to be produced in substantial quantities.Gunston 1980, p. 22.
Design Overview
The SM.79 was a cantilever low-wing monoplane trimotor, with a retractable taildragger undercarriage.Apostolo 1967, p. 5. The fuselage had a welded tubular steel framework covered with duralumin on the forward section, a mixture of duralumin and plywood across the upper fuselage surface, and fabric for all of the other exterior surfaces.Mondey 1996, p. 236. The wings were of all-wood construction, with trailing edge flaps and leading edge slats (Handley Page style) to offset their relatively small size. The structure consisted of three spruce and plywood spars, linked with plywood ribs, with a skin of plywood.Air International July 1984, p. 27. The wing had a dihedral of 2° 15'. The ailerons were capable of rotating through +13/-26°, and were used together with the flaps in low-speed flight and in takeoff. The aircraft's capabilities were significantly greater than its predecessor, the SM.75, with over available and a high wing loading that gave it characteristics not dissimilar to a large fighter.
The engines fitted to the main bomber version were three Alfa Romeo 126 RC.34 radials, driving variable-pitch, all-metal three-bladed propellers.Apostolo 1967, pp. 4–5. Speeds attained were around at , with a relatively low practical ceiling of . Cruise speed was at , but the best cruise speed was (60% power). The landing was characterized by a final approach with the slats extended, slowing to with extension of flaps, and finally the run over the field with only needed to land (2,050 rpm, 644 Hg pressure).
The SM.79 was typically operated by a crew of five (or a crew of six upon the bomber version). The cockpit was designed for the accommodation of two pilots seated in a side-by-side configuration. Instrumentation in the central panel included oil and fuel gauges, altimeters for low () and high altitude (), clock, airspeed and vertical speed indicator, gyroscope, compass, artificial horizon, turn and bank indicator, rev counters and throttles.Sgarlato 2002, p. 21.
Performance
The SM.79's performance was considered fairly strong.Gunston 1980, p. 183. Its rate of climb was fairly high, it was fairly fast for its time, and was both rugged and responsive enough to allow it to be looped (with care). Its wooden structure was light enough to allow it to stay afloat for up to half an hour in case of water landing, giving the crew ample time to escape, and the front engine offered some protection from anti aircraft fire. With full power available and flaps set for takeoff, the SM.79 could be airborne within before quickly climbing to an altitude of within the space of 3 minutes, in 6 minutes 30 seconds, in 9 minutes 34 seconds, in 13 minutes 2 seconds, and in 17 minutes 43 seconds.Sgarlato 2002, p. 45.
The bomber version had 10 separate fuel tanks that had a maximum combined capacity of .Apostolo 1967, p. 4. Endurance when flown at full load was reportedly around 4 hours 30 minutes at an average speed of . The maximum ferry range, when flown at its optimal cruise speed, was unconfirmed; in order to reach Addis Ababa with non-stop flights from Libya, SM.79s were frequently modified in order to carry more fuel, and were able to fly over . The range (not endurance) with payload was around .