Piaggio P.108
The Piaggio P.108 was Italy's only four-engine heavy bomber of the Second World War, an all-metal design by Giovanni Casiraghi that first flew on 24 November 1939 and entered Regia Aeronautica service in 1941. Production was very small and is accounted differently by the sources used here: both Wikipedia articles count 24 P.108B bombers and a single P.108A anti-ship aircraft, while Italian Wikipedia gives a combined total of 35 aircraft across all versions and prototypes, against the higher figures in English Wikipedia's infobox and text. The bombers served with a single squadron on night raids against Gibraltar, Algeria and Sicily, and the P.108T transports passed to the Luftwaffe, which flew nine of them until 1945.
Why It Mattered
The Piaggio P.108 was the only four-engine strategic bomber that the Regia Aeronautica operated during the Second World War. It was designed by Giovanni Casiraghi, a Piaggio engineer whose years working in the United States between 1927 and 1936 shaped an aircraft unlike Italy's familiar trimotor bombers. The prototype flew on 24 November 1939, the type entered service in 1941, and all of its bombers went to a single squadron. Output stayed tiny: both Wikipedia articles count 24 bombers and a single gun-armed anti-ship aircraft, and Italian Wikipedia puts the combined total for every version, prototypes included, at 35. English Wikipedia counts the P.108 among the handful of Italian combat aircraft able to match the best Allied types of the war.
Design Notes
Casiraghi's bomber was an all-metal, low-wing monoplane with retractable landing gear and four engines. Four Piaggio P.XII eighteen-cylinder radial engines powered it, and English Wikipedia describes those engines as among the most powerful of their day but unreliable. Its defensive armament broke new ground: remote-controlled turrets sat in the outer engine nacelles, sighted by operators in fuselage cupolas, an arrangement English Wikipedia calls the design's most innovative aspect. The internal bomb bay held up to 3,500 kg of bombs, yet its division into three lengthwise sections kept the heaviest single bombs out. The bomber airframe branched into specialised versions, among them the single P.108A, which carried a 102 mm gun for anti-ship work. The P.108C airliner widened the fuselage to seat 32 passengers, while the P.108T was an unpressurised transport designed from the outset for military use.
Operational History
Every bomber went to a single unit, the 274a Squadriglia, which received the type in 1941. On 7 August 1941 the squadron's commander, Bruno Mussolini, son of the Italian dictator, was killed when the prototype he was flying on a training flight came down too low and struck a house; Italian Wikipedia records that two other airmen died with him. Combat began on 6 June 1942 with an unsuccessful daylight mission against a destroyer. Three weeks later five aircraft left Decimomannu in Sardinia on a night raid against Gibraltar; one turned back with engine trouble and three, short of fuel, force-landed in Spain. English Wikipedia judges that the Gibraltar sorties still met their strategic purpose, obliging the Allies to concentrate resources on defending the exclave. After the Allied invasion of French North Africa, the squadron turned to Algerian targets such as Bône, Algiers and Oran, and at least three aircraft were lost over Africa, most of them claimed by Beaufighter night fighters. The bomber's final operations came over Sicily, where between 11 and 22 July 1943 the reinforced squadron flew 12 sorties against the invasion force. Of the 24 bombers built, English Wikipedia counts six lost to enemy action, four to accidents and three to forced landings.
Afterlife
When the Italian armistice was declared on 8 September 1943, nine bombers remained, and eight of them were sabotaged so they would not fall into German hands. The last airworthy bomber was flown to southern Italy, where a landing accident ended its career. Italian Wikipedia notes that the few bombers the Luftwaffe did requisition after the armistice were never flown operationally. The transports served on: nine P.108Ts flew with Luftwaffe transport units until the war ended, mainly on the Eastern Front. The end came in 1945, when English Wikipedia records the remaining transports destroyed in air raids, lost in flying accidents, or destroyed or captured as Germany collapsed.