Savoia-Marchetti SM.75

The Savoia-Marchetti SM.75 Marsupiale (Marsupial) was an Italian passenger and military transport aircraft of the 1930s and 1940s. It was a low-wing, trimotor monoplane of mixed metal and wood construction with a retractable tailwheel undercarriage. It was the last of a line of transport aeroplanes that Alessandro Marchetti began building in the early 1930s. The SM.75 was fast, robust, capable of long-range flight and could carry up to 24 passengers for 1,000 miles.

SM.75 and SM.75bis
The SM.75 was designed in response to an enquiry from the Italian airline Ala Littoria, which was seeking a modern, middle-to-long-range airliner and cargo aircraft as a replacement for its Savoia-Marchetti S.M.73 aircraft. In his design of the SM.75, Savoia-Marchetti chief designer Alessandro Marchetti (1884–1966) retained the general configuration of the S.73 but introduced retractable main landing gear to reduce aerodynamic drag. The SM.75's airframe consisted of a steel-tube frame with fabric and plywood covering, and its control surfaces were plywood-covered. The SM.75 had a four-man crew, and its cabin was built to accommodate up to 25 passengers. Its short take-off run of 337 metres (1,105 feet) and shorter landing distance of 280 metres (919 feet) meant that it could operate from short runways on secondary airfields.

The SM.75 was powered by three Alfa Romeo 126 RC.34 radial engines rated at 559 kilowatts (750 horsepower) each at 3,400 meters (11,155 feet). Eleven aircraft fitted with three Alfa Romeo 126 RC.18 14-cylinder engines rated at 641 kilowatts (860 horsepower) at 1,800 metres (5,905 feet) were designated the SM.75bis.

The Regia Aeronautica (Italian Royal Air Force) showed solid interest in the SM.75, resulting in the development of a militarized version. This lacked windows in the passenger cabin but was fitted with a reinforced panel to permit the installation of a dorsal gun turret. It was powered by three Alfa Romeo 128 RC.21 engines and had a greater cargo capacity than the SM.75, and entered military service as the Savoia-Marchetti SM.82.

SM.76
The Italian airline LATI received its first SM.75 in 1939. The aircraft was redesignated as the SM.76 in 1940.

SM.87
In 1939, a floatplane version of the SM.75 appeared. Known as the SM.87, it was powered by three 746 kW (1,000 hp) Fiat A.80 engines. It could reach a speed of 365 km/h (227 mph) and had a ceiling of 6,250 m (20,510 ft), a range of 2,200 km, and a crew of four, and could accommodate 24 passengers. Four were built.

SM.90
The SM.90 was a version of the SM.75 fitted with more powerful 1,044 kW (1,400 hp) Alfa Romeo 135 R.C.32 engines. It had a longer fuselage than the SM.75. Only one was built.

SM.75GA
The SM.75 GA (for Grande Autonomia, meaning "Long Range") was a modofication of the SM.75 powered by three 641 kW (860 hp) Alfa Romeo 128 engines and fitted as well as a powerful radio and auxiliary fuel tanks to boost the aircraft's range to 7,000 kilometers (4,350 statute miles) with a 1,100-kilogram (2,430-pound) load. With a four- or five-man crew and a 200-kilogram (441-pound) load, the SM.75 GA could achieve a range of 8,005 kilometers (4,971 statute miles) at 298 kilometers per hour (185 miles per hour) flying at altitudes between 3,500 and 5,000 meters (11,483 and 16,404 feet).

Italian commercial service
The SM.75 first flew in November 1937 from Novara, in Piedmont. It entered commercial service with Ala Littoria in 1938 and with LATI in 1939, and was employed on services both within Europe and to South America, as well as on the Rome-Addis Ababa route established after the Italian invasion—and later conquest—of Abyssinia in the Second Italo-Abyssinian War. The SM.75 proved easily capable of carrying a crew of four and 17 passengers and their baggage a distance of 1,721 km at 362 km per hour at 4,000 meters (13,123 feet), and it established a number of world records for speed-over-distance-with-payload and closed-circuit distance. One SM.75 was modified to set endurance world records, and succeeded in 1939 when it covered around 12,000 km.

After Italy entered World War II on 10 June 1940, civil SM.75s continued to perform supply operations to Italy' overseas territories, which dwindled as the war progressed, until the Italian armistice with the Allies went into effect on 8 September 1943. They also continued to operate services to South America until December 1941, when Italy declared war on the United States.

Italian military service
After Italy entered World War II in June 1940, the Regia Aeronautica needed aircraft with which to maintain contact with Italy's imperial possessions -- Abyssinia, Italian Somaliland, and Eritrea -- in East Africa, which were surrounded by British-controlled territories and military forces. Available SM.75s were militarized by the installation of a 12.7-millimeter (0.5-inch) Breda-SAFAT machine gun mounted in a Caproni-Lanciani gun turret and the introduction of a fifth crewman to man it, and new SM.75s were manufactured to a modified design allowing them to carry up to 24 troops over long distances and with the same performance as the airliner version.

Special missions
There were several notable missions flown mainly for propaganda purposes.

Leaflet mission to Asmara
In January 1942, the commander-in-chief of the Regia Aeronautica, General Rino Corso Fougier, began plans for a long-range flight from Rome to Tokyo. He consulting with pilots with recent experience in long-range flights to South America and East Africa, and reached a consensus that the SM.75 was better suited for the mission than either the SM.82 or the Savoia-Marchetti SM.83 because of its superior endurance, albeit at the expense of defensive armament and self-sealing fuel tanks. The SM.75 aircraft selected for the flight, serial no. MM.60537, was modified to become the first long-range SM.75 GA aircraft.

The first mission of the SM.75 GA was to drop propaganda leaflets saying "Italian colonists, Rome is not forgetting you. We shall come back!" over British-held territory in East Africa previously occupied by the Italians. A five-man crew led by Lieutenant Colonel Amadeo Paradisi, who piloted the aircraft, flew from Rome to Benghazi in Libya. The mission began at 17:30 hours on 7 May 1942, when the SM.75 GA set out from Benghazi on the 2,700 km first leg, flying at a planned 3,000 meters (9,842 feet), although bad weather forced Paradisi to climb to 4,000 meters (13,123 feet). After 10 hours and 20 minutes, the SM.75 GA arrived over Asmara in Eritrea and released the leaflets, but instead of returning as planned to Benghazi, Paradisi flew directly to Rome, first at 3,500 meters (11,482 feet), and then at 5,200 meters (17,060 feet) to optimize fuel consumption. The entire mission had lasted 28 hours.

At Rome, mechanics conducted several trials with the plane. On 11 May 1942, two days after it arrived in Rome, the SM.75GA suffered a simultaneous breakdown of all three of its engines during a 50 km ferry flight from Rome to Guidonia Montecilio. Paradisi made an emergency landing in which the aircraft was destroyed and he lost a leg, although the rest of the crew avoided injury.

Rome-to-Tokyo flight
After the loss of the first SM.75 GA, a second SM.75, serial number MM.60539, was modified to SM.75 GA standard for the Rome-to-Tokyo flight. Ready on 9 June 1942, it was designated the SM.75 GA RT (for "Rome-Tokyo"). Its pilot, Lieutenant Colonel Antonio Moscatelli, was placed in charge of the overall operation, which in addition to providing Italy with propaganda about Italian aviation prowess was to carry new codes for communications between Japan and her Axis partners; the Italians believed the British had broken the existing codes. The flight was made difficult to perform by the extreme distance involved and the need to fly thousands of kilometers through the airspace of the Soviet Union, a country with which Italy was at war.

Taking off from Guidonia Montecelio at 05:30 hours on 29 June 1942, the SM.75 GA RT landed later that day 2,030 km away at Zaporozhye in German-occupied Ukraine, the easternmost airfield available to the Axis powers. At 18:00 hours on 30 June 1942, carrying no documents or correspondence that might embarrass the Japanese (who were not at war the with Soviet Union) and with its crew under orders to burn the aircraft and its documents if forced down in enemy-held territory, the overloaded SM.75 GA RT made the difficult and potentially dangerous takeoff from the grassy 700-meter (2,297-foot) runway at Zaporozhye, weighing 21,500 kilograms (47,400 pounds) while having 11,000 kilograms (24,250 pounds) -- 10,340 liters (2,721 gallons) -- of fuel on board. Operating under strict radio silence, the aircraft continued unscathed through the night—despite encountering Soviet anti-aircraft fire, bad weather conditions, and a Soviet fighter, probably a Yakovlev Yak-1 -- flying over the north coast of the Aral Sea, skirting Lake Baikal and the Tarbagatai Mountains and over the Gobi Desert. Maps of Soviet positions proved inaccurate, and Moscatelli had to climb to 5,000 meters (16,404 feet) to avoid detection, causing the aircraft's oxygen supply to run out earlier than planned. A sandstorm over Mongolia also endangered the SM.75 GA RT, but its crew sighted the Yellow River at 22:00 hours on 30 June 1942 and, on the last of its fuel, landed 6,000 km east of Zaporozhye on the 1,300-meter (4,270-foot) runway, at Pao Tow Chien, over 1,000 meters (3,280 feet) above sea level in Japanese-occupied Inner Mongolia, at 15:30 hours on 1 July 1942. The aircraft was painted with Japanese markings so that it would be safe in Japanese airspace, took an interpreter aboard, and then flew the final 2,700 km leg of the journey to Tokyo.

The SM.75 GA RT departed Tokyo on its return journey on 16 July 1942. Arriving at Pao Tow Chien, its Japanese markings were removed and replaced with Italian ones. It took off at 21:45 hours on 18 July 1942 from Pao Tow Chien, retraced its route, and, after 29 hours and 25 minutes in the air and having covered 6,350 km, it landed at Odessa in the Ukraine. Moscatelli then completed the operation by flying the aircraft on to Guidonia Montecelio. The Italians publicised this event on 2 August 1942 despite the Japanese government's reluctance for diplomatic reasons, which cooled relations between the two countries; the Italians made no attempt to repeat the flight.

Bombing mission to Abyssinia
In 1943, two SM.75 GA aircraft undertook a bombing mission, the only one made by an SM.75, intended to destroy American bombers stored at an airbase in Gura in Abyssinia. To reach the objective, which was over 3,000 km away, the two S.75 GAs—with civil registration I-BUBA and I-TAMO, but renominated with serial numbers MM.60539 and MM.60543, respectively. for military use—were laden heavily with 11,000 kilograms (24,250 pounds) of fuel, and modified by fitting a "Jozza" bomb-aiming system and a bomb bay capable of carrying 1,200 kilograms (2,650 pounds) of bombs. The most experienced crews were selected for the mission, led by officers named Villa and Peroli.

The mission started at 06:30 hours on 23 May 1943 from Rhodes, the easternmost Regia Aeronautica base at the time. Each of the two aircraft, weighing 10,200 kilograms (22,490 pounds) empty, had a takeoff-weight of 24,000 kilograms (52,910 pounds). The SM.75 GA's engines were optimized for endurance and economy rather than for power, which made the takeoff difficult with the heavy load of fuel and bombs. Initially flying at low altitude, at 10:00 hours the modified SM.75 GAs climbed to 3,000 meters (9,842 feet). Having used an excessive amount of fuel, Peroli diverted to bomb Port Sudan instead; he returned safely to Rhodes at 05:30 hours on 24 May 1943 after 23 hours in the air. Villa, meanwhile, pressed on alone and arrived over the Gura airbase—which was heavily defended despite being well behind the front line—at 18:45 hours and released his bombs. Although one bomb failed to drop and remained on board, presenting the threat of an explosion, Villa's mission was successful, and his aircraft returned to Rhodes safely one hour and 15 minutes after Peroli, landing at 06:45 hours on 24 May 1943, having covered 6,600 km over a period of 24 hours and 15 minutes.

Italian Co-Belligerent Air Force
After Italy surrendered to the Allies in September 1943, some SM.75s entered service with the Italian Co-Belligerent Air Force, which fought on the Allied side for the remainder of the World War II.

Only few aircraft survived the war and actually remained in service until 1949.

Hungary
Italy exported five SM.75 aircraft to Hungary for service with the Hungarian airline MALERT. After Hungary entered World War II, these aircraft were pressed into service with the Magyar Királyi Honvéd Légierő (MKHL), Hungarian Air Force. During the short conflict against Yugoslavia, in the afternoon of 12 April 1941, four SM.75s, loaded with paratroopers, took off from Veszprém. Unfortunately, the leading aircraft, code E-101, crashed immediately afterwards. Twenty three Hungarians lost their lives, including 19 paratroopers. It was the heaviest loss in the war against Yugoslavia. On 6 May 1941, the Hungarian Air Force had at its disposal four S.M.75, as paratroop transport.

Germany
After Italy surrendered to the Allies in September 1943, Germany seized some SM.75s which entered service with the Luftwaffe.

Variants

 * SM.75
 * Civilian airliner and cargo aircraft; some later militarized for Regia Aeronatica use as cargo aircraft and troop transports


 * SM.75bis
 * Up-engined version of SM.75 civilian airliner


 * SM.75 GA
 * Long-range version of SM.75


 * SM.76
 * 1940 redesignation of aircraft delivered to the Italian LATI airline


 * SM.87
 * Floatplane version of SM.75


 * SM.90
 * Re-engined version of SM.75 with longer fuselage

Military operators

 * 🇩🇪 Germany
 * Luftwaffe
 * 🇭🇺 Hungary
 * Royal Hungarian Air Force operated 5 aircraft
 * 🇮🇹 Italy
 * Regia Aeronautica
 * Italian Co-Belligerent Air Force

Civil operators

 * 🇮🇹 Italy
 * Ala Littoria - 34 in operation by June 1940
 * 🇭🇺 Hungary
 * MALERT