Savoia-Marchetti SM.75

SM.75 Marsupiale
Type	Civil airliner & military transport
Manufacturer	Savoia-Marchetti
Maiden flight	1937
Introduced	1938
Status	out of service
Primary users	Italy Hungary
Number built	95

The Savoia-Marchetti SM.75 Marsupiale was an Italian passenger and military transport aircraft of the 1930s and 1940s. The SM.75 first flew in 1937. It was a low-wing, monoplane trimotor of mixed-construction; with a retractable, tailwheel undercarriage.

Development

The SM.75 was designed in response to an enquiry from Ala Littoria who were seeking a replacement for their S.73s. Savoia-Marchetti retained the general configuration of the earlier machine but introduced retractable main landing gear to reduce drag. The airframe consisted of a steel-tube frame with fabric and plywood covering; the control surfaces were plywood covered. The cabin was built to accommodate up to 25 passengers.

Eleven SM.75bis aircraft were fitted with three Alfa Romeo 126 RC.18 radial piston engines.

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

In 1939, a floatplane version known as the SM.87 was created, powered by three 1,000 hp Fiat A.80 engines. It could reach a speed of 365 km/h, had a ceiling of 6,250 m and a range of 2,200 km, a crew of four, and could accommodate 24 passengers. Four were built.

The SM.90 was a version fitted with more powerful 1,044 kW Alfa Romeo 135 R.C.32 engines, and had a longer fuselage, but only one of these aircraft was built.

Operational history

The SM.75 entered commercial service in 1938 and was employed on services both within Europe and to South America as well as the Rome-Addis Ababa route established after the Italian invasion of Abyssinia. It established a number of records for speed-over-distance-with-payload and closed-circuit distance. One SM.75 was prepared to set endurance world-records; succeeding in 1939 when it covered around 12,000 km.

Five aircraft were exported to Hungary.

The Regia Aeronautica showed solid interest in the type 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, forming the basis of the SM.82.

After Italy entered World War II in June 1940, civil SM.75s began to be pressed into military service. However, they continued to operate services to South America until December 1941, when Italy declared war on the United States. For the next three years, the type continued to perform supply operations to the country's dwindling territories.

There were several notable missions flown mainly for propaganda purposes.

The first mission was to drop propaganda pamphlets over territory in East Africa previously occupied by the Italians, and involved an SM.75GA (Grande Autonomia), serial no. MM.60537, which was powered by 860 hp Alfa Romeo 128 engines; and was fitted with auxiliary fuel tanks to boost the range to 7,000 km with a 1,100 kg load, as well as a powerful radio. Paradisi's crew flew from Rome to Benghazi, from where the mission commenced. At 17:30, on 7 May 1942, the aircraft set out on the 2,700 km first leg, flying at 3,000 m; but bad weather conditions were encountered and so the aircraft climbed to 4,000 m. After 10 hours and 20 minutes the aircraft arrived over Asmara and released the pamphlets, but instead of returning as planned to Benghazi, it flew directly to Rome, first at 3,500 m, and then at 5,200 m to optimize fuel consumption. The SM.75 was chosen for this mission in preference to the military SM.82 version because of its superior endurance, albeit at the expense of defensive armament and self-sealing fuel tanks. The entire mission lasted for 28 hours, but the aircraft crashed two days later during a short ferry mission.

The second was a bombing mission, the only one made by an SM.75, intended to destroy American bombers stored at an airbase in Gura, Ethiopia. To reach the objective which was over 3,000 km away; two S.75GAs, I-BUBA and I-TAMO, renominated MM.60539 and MM.60543 for military use; were heavily laden with 11,000 kg (14,000 l) of fuel, and modified by fitting a "Jozza" aiming system, together with a bomb bay capable of carrying 1,200 kg of bombs. The most experienced crews were selected for the mission, led by Villa and Peroli.

The mission started at 06:30 on 23 May 1943 from Rodi, the eastern airbase of the Regia Aereonautica at the time. Each of the two aircraft, weighing 10,200 kg unladen, had a takeoff-weight of 24,000 kg. The engines were optimised for endurance and economy rather than for power, which, in addition to the heavy fuel and bombloads, made the takeoff difficult. Initially flying at low altitude, at 10:00 the modified SM.75GAs climbed to 3,000 m, but having used an excessive amount of fuel, Peroli's aircraft diverted to bomb Port Sudan instead. Villa's aircraft arrived over the Gura airbase at 18:45, which was heavily defended despite being well behind the front-line, and released its bombs, but one remained on-board presenting the threat of an explosion. The mission was successful, and the aircraft returned to Rodi one hour and 15 minutes after Peroli, landing at 06:45 the following morning, having covered 6,600 km over a period of 24 hours and 15 minutes.

A mission to Tokyo was undertaken in May 1942, by SM.75 MM.60539 with a crew led by Antonio Moscatelli, to carry new codes for communications between Japan and her Axis partners, believing the British had broken the existing ones. This task was made difficult to perform by the extreme distance involved and the need to fly thousands of kilometres through forbidden Russian airspace. Taking off from Guidonia on 29 June 1942, the aircraft later landed 2,030 km away at Aporoskje, the most easterly airfield available. At 18:00 the following day, the 2,500 hp aircraft made the difficult and potentially dangerous takeoff from the grassy 700 m runway, weighing 21,500  kg while having 11,000 kg of fuel on board. The aircraft continued unscathed through the night, despite anti-aircraft fire, bad weather conditions, and being pursued by a fighter, to land 6,000 km to the east at 15:30 at Pao Tow Chien before the final 2,700 km leg of the journey to Tokyo. When it was discovered by Japanese technicians that the SM.75GA was incapable of reaching them without overflying the USSR, it was thought prudent for the Italian crew to make the return journey ten days later without any publicity. The aircraft took off at 21:45 from Pao Tow Chien's 1,300 m runway, over 1,000 m above sea level, and after 29 hours and 25 minutes and having covered 6,350 km, it landed at Odessa. 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.

Operators

Military operators

Template:Country data Germany

• Luftwaffe

Template:Country data Hungary

• Hungarian Air Force operated 5 aircraft

Template:Country data Italy

• Regia Aeronautica
• Italian Co-Belligerent Air Force

Civil operators

Template:Country data Italy

• Ala Littoria - 34 in operation by June 1940

Specifications (SM.75)

Data from

General characteristics

• Crew: 4 (+1 gunner in military use)
• Capacity: 18-25 passengers or 25 troops
• Length: 21.6 m (70 ft 10 in)
• Wingspan: 29.68 m (97 ft 4 in)
• Height: 5.1 m (16 ft 9 in)
• Wing area: 118.6 m² (1,276.14 ft²)
• Max takeoff weight: 13,000 kg (28,600 lb)
• Powerplant: 3× Alfa Romeo 126RC.34 radial piston, 559 kW (750 hp) each

Performance

• Maximum speed: 363 km/h (195 knots, 224 mph)
• Range: 1,720 km (928 nm, 1,061 mi)
• Service ceiling: 6,250 m (20,500 ft)

See also

Related development
Savoia-Marchetti SM.82 Comparable aircraft

• Douglas DC-3
• Junkers Ju 52/3m

References

• Lembo, Daniele, gli ultimi voli sull'impero, Aerei nella storia n.23, April-May 2002.
• Pellegrino, Adalberto, Il raid segreto Roma-Tokyo, Storia militare n.45, June 1997