The Piaggio P.108 B was the only heavy four-engine bomber to see service with the Italian air force (Regia Aeronautica) during World War Two. Due to the lack of production capacity of the Italian aviation industry, too few were built to play a significant role in this conflict. In total Piaggio built only 163 P.108 Bs, but this fact does not make the design less remarkable.
The Piaggio P.108 B (Bombardiere) was an all metal cantilever low-wing monoplane with an retractable undercarriage, driven by four Piaggio P.XII RC 35 18 cylinder radial engines, each producing 1350 hp. The first prototype was finished in October 1939 and had a very advanced defensive armament for its day. Not only had the Piaggio two 7,7 mm machine waist guns, a 12,7 mm machine gun in the lower turret and a similar weapon in the nose turret, but also two remotely-controlled twin gun turrets in outer engine nacelles. The first Allied bomber with a similar armament was the Boeing B 29, which was developed four years later.
The bomb load of the Piaggio comprised of 3.500 kg, all carried internally in the bomb bay. In comparison, the Boeing B-17 Flying Fortress had a maximum internal bomb load of only 2.200-kg.
The only unit of the Regia Aeronautica ever to fly the Piaggio P.108 B was the 274a Squadrilia Bombardamento a Grande Raggio (B.G.R.), the 274th Long-Range Bombardment Group. This unit was formed in May 1941, around the first machines that came off the assembly lines.
The training of the crews lasted far longer than anticipated. It there took until June 1942 before the 274a B.G.R. became operational. The most spectacular raids with the Piaggio P. 108 B were flown in October 1942, when the Regia Aeronautica launched several night attacks on Gibraltar, from the airfield of Decimomannu on Sardinia.
Several versions were derived from the Piaggio P. 108 B, such as the P.108 A (Artigliere), which had a 102 mm anti-shipping gun in it’s nose, the P.108 C (Civile) airliner and the P.108 T (Trasporto). The latter two versions had a newly designed fuselage of larger diameter, for the transportation of passengers or freight. They were hardly used by the Regia Aeronautica, the main user being the German Luftwaffe. In September 1943, after the Italian armistice, the Luftwaffe had captured all fifteen built P.108 Cs and P.108 Ts. They were used at the Russian front, as part of Luftflotte 2, where they performed sterling duties, among others during the evacuation of the Crimea in 1944.
In 1940 a seaplane version of the P.108 was designed, the P.108 B.I. (Bombardiere Idrovolanti), but this was never developed beyond the stage of a wooden scale model.
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