Savoia-Marchetti SM.81 Pipistrello
The Savoia-Marchetti SM.81 Pipistrello was an Italian three-engined bomber and transport aircraft designed by Alessandro Marchetti as a military derivative of the S.73 airliner, first flown in 1934 and in service from 1935. It fought in Ethiopia and in the Spanish Civil War before the Second World War, then, too slow for daylight bombing, served the Regia Aeronautica chiefly as a night bomber and transport until 1943, with a few aircraft flying on to 1944. Published production accountings range from 530 to more than 570 aircraft and do not reconcile. The last examples were retired by 1950.
Why It Mattered
The SM.81 was the first three-engined bomber-transport to serve with the Regia Aeronautica, a military derivative of the S.73 airliner shaped by Italo Balbo's wish for an aircraft able to serve Italy's African colonies. English Wikipedia describes it as fast, well armed and long-ranged when it appeared in 1935, and Italian Wikipedia calls it one of the most modern bombers in the world at its entry into service. It fought in Ethiopia and Spain before the Second World War began, and the aircraft sent to Spain were among the first the fascist powers sent to Franco's aid. Slow by 1940, it stayed in service because its roomy fuselage and sturdy build suited transport work, and English Wikipedia judges it one of the most flexible, reliable and important aircraft the Regia Aeronautica operated between 1935 and 1944.
Design Notes
Alessandro Marchetti designed the SM.81 in parallel with the S.73 airliner, keeping that aircraft's cantilever wing but giving the military type a simpler fuselage and a fixed tailwheel undercarriage. Construction was mixed: a steel-tube fuselage framework, metal-covered aft and wood-and-fabric elsewhere, with an all-wood three-spar wing. Six crew flew it, the pilots side by side in an enclosed cockpit and the bombardier in a glazed, semi-retractable gondola beneath them. Its six 7.7 mm machine guns, two of them in powered retractable turrets, were heavy defensive armament for 1935, and its two-part bomb bay took up to 2,000 kg of bombs over short ranges. Production aircraft flew with a wide range of radial engines from Alfa Romeo, Piaggio and Gnome-Rhône, and a single twin-engined prototype, the SM.81B, performed worse and was not taken further. No armour was fitted beyond self-sealing fuel tanks. A VIP version was also built in some numbers; Mussolini flew one personally, and its slowness earned it the nickname "Turtle". Italian Wikipedia ties the Pipistrello, or bat, nickname to the type's later night missions.
Operational History
The prototype flew from Vergiate on 8 February 1934 with test pilot Adriano Bacula at the controls, and deliveries began in April 1935 to the 7º Stormo. The first production series was 100 aircraft, and production was spread across SIAI and seven other Italian firms so numbers could be built up quickly. In Ethiopia the type was quickly adapted to bombing, strafing, close air support and reconnaissance, and 36 aircraft remained there afterward in support of the occupation. On 28 July 1936 twelve SM.81s, disguised as Spanish civilian aircraft, flew troops from Sardinia to Morocco for Franco; only nine reached Melilla. Their bombs then helped keep the Republican fleet away from the convoys carrying the Army of Africa to Spain. Between 90 and 100 SM.81s served in Spain, and at least 64 were left behind there at the end of 1938. When Italy entered the Second World War in June 1940 around 300 remained in service, and the first Italian aircraft into action in East Africa were two SM.81s on 11 June 1940, one attacking Port Sudan and the other reconnoitring over the Red Sea. Too slow and vulnerable by day, the type was restricted to second-line duties and transport, but at night it remained an effective bomber, particularly over North Africa. SM.81s sent to Russia during the Stalingrad battle were all lost there. After the September 1943 armistice, four aircraft kept flying with the Italian Co-Belligerent Air Force into December 1944, while in the north a transport group under German command flew the type on the Eastern Front, and none of that group's aircraft survived the war.
Afterlife
The production accountings in the sources do not reconcile: English Wikipedia's main article gives 535 built, its companion operational-history article totals the eight builders at 530 plus the one twin-engined example, and Italian Wikipedia gives more than 570, so the record states the range rather than a single figure. The aircraft left behind in Spain passed to the Spanish Air Force. Several aircraft survived the war to serve with the postwar Aeronautica Militare Italiana, but all of them had been retired by 1950.