Piaggio P.108 Four-Engine Heavy Bomber
The Piaggio P.108 served as the only Italian four-engine heavy bomber in World War 2.
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The Piaggio P.108 was a multi-faceted airframe developed to fulfill a variety of roles for the Italians during World War 2. She was conceived in four distinct forms of which only three were ever produced in any number. The type served as Italy's only four-engined heavy bomber of the war and featured several innovations that separated her from the proverbial pack. Despite her promising stature, the bomber was plagued by technological issues and engine reliability for much of her career, seeing only limited combat actions as a bomber and further service as troop transports by the end of the war.
Giovanni Casiraghi designed the all-metal Piaggio P.108 based on the all-wood P.50. Casiraghi garnered valuable experience during his time as an engineer during the "Golden Age of Flight" while in the United States for nearly a decade (1927 to 1936). The initial model P.50 was a similar large, heavy bomber design with a four-engines set as a tandem "pusher/puller" arrangement along the wings. It appeared in 1937 and construction included two prototypes. The aircraft was not ordered into production by the Italian government. The P.50-II appeared in 1938 and sported four radial pistol engines in a more conventional "puller" layout. A single prototype was constructed but the type was also not ordered by the Italian powers. However, the design and the development of these large aircraft played a crucial role in bringing the upcoming P.108 to fruition. In a government-sponsored competition for a new modern bomber to serve the Regia Aeronautica, the P.108 design won out over its competitors.
From the outset, the P.108 was planned in four distinct versions requiring a flexible airframe. The P.108A "Artiglieri" would become a dedicated anti-shipping platform to protect Italian interests across the Mediterranean Sea - this model armed with an Ansaldo 1941 Model 90/53mm cannon and torpedoes for the job. The P.108B "Bombardiere" would become the dedicated workhorse and heavy bomber platform of the Regia Aeronautica. The P.108C "Civile" was to be a 32-seat civilian passenger airliner while the P.108T "Transporto" was to become its militarized transport form - serving up to 56 combat-ready troops.
In the end, only one promising (and tested) P.108A was produced due to Italian priorities. However, quantitative production was seen out of the P.108B, P.108C and P.108T types but the Bombardiere remained the notable production model in the P.108 family. The P.108M "Modificato" was to be a modified P.108B with improved armament but this was never built. The P.133 was another proposed advanced version of the P.108 with better engines and an improved bomb load but this was never completed. One of the more unique design elements of the P.108 bomber version was its use of remote-controlled machine gun mounts fitted to the trailing end of each outer engine gondola to help protect the aircraft against attacks from the rear - an unproven and novel concept at best.
The prototype P.108 achieved first flight on November 24th, 1939. However, the P.108 in its operational form would not be delivered to the Regia Aeronautica until May of 1941. Technical difficulties in the advanced design also delayed the P.108B for another year before being deployed with the 274th Long Range Bomber Squadron. Furthermore, a general lack of government and industry support of the P.108B model in particular helped to diminish her possible wartime success. Just 163 total P.108 examples of all variants were completed by the time production stopped in 1943. The P.108C and P.108T models proved the more reliable aircraft in the end.
The P.108 in Action
The P.108 proved an innovative bomber aircraft for her time and could match the strongest qualities of her Allied contemporaries. Of particular note were her advanced wings and their integrated turrets - innovative yet overly complex and questionable in their implementation into the final design. Unfortunately for the Regia Aeronautica, there were never more than seven or eight P.108s available at any one time. To add insult to injury, the P.108 proved a poor-handling bomber design once in practice and engine reliability soon took its toll. The models that were airworthy saw action over the Mediterranean Sea, though mostly concentrated during the span of 1942 and 1943 before the Italian surrender. The Piaggio P.108 was used in nighttime raids on Allied ports based in Algeria and Gibraltar during the Operation Torch landings. Operation Torch was launched in November of 1942 and was the first major Allied operation to include quantitative military forces from America - the operation began the Allied campaign across French North Africa in an effort to take away Italian and German staging areas on the African continent. In all, there were 55 recorded bombing sorties involving the P.108B with last actions being seen over Sicily.
End of the Road
As the war progressed, many of the existing passenger airliner models were eventually converted to the military-minded P.108T transport types within time. By the time of the Italian surrender in September of 1943, only about 5% of the entire P.108 bomber force remained intact, many falling to Allied guns in the air or whilst they rested on the ground. Some were sabotaged to avoid them being used further by Axis powers moving to the north. Whatever systems remained with the Axis were pressed into service with the relocated Fascist Italian forces under Mussolini in Northern Italy with at least nine serving with German Luftwaffe groups as emergency transports until Germany's finale in May of 1945.
Piaggio P.108 Walk-Around
Design of the Piaggio P.108 was conventional of bombers of the time. She sported a smooth long fuselage with a stepped forward section. The nose featured glazing and showcased some of her defensive armament. The cockpit rested along the third highest "step" and her crew was made up of six or seven personnel to include a pilot, co-pilot, bombardier and machine gunners. Cabin blisters were easily identifiable along the top side of the fuselage, these housing the crewmembers charged with manning the remote-controlled wing machine gun turrets. Wings were fitted as low-mounted assemblies ahead of amidships. The fuselage tapered off into the empennage which was affixed with a conventional tail system. There was a single, large-area vertical tail fin and low-mounted stabilizers. All wing surfaces were rounded in shape, consistent with many of the other Italian aircraft designs of the war. Each wing held a pair of engines along their leading edges. There was slight dihedral to each wing, giving a pronounced upward angle from wing root to wing tip. The undercarriage featured two retractable single-wheeled main landing gear legs and a fixed tail wheel. The main legs retracted forward into and under the inner most engine nacelles.
Power for the P.108
Power was derived from four Piaggio PXII RC.35 radial piston engines delivering approximately 1,500 horsepower from each. This provided for a top speed of 267 miles per hour with a service ceiling of about 28,300 feet and a range out to 2,185 miles. The engines never proved wholly reliable, limiting the P.108B in every area. She maintained an empty weight of 38,161lbs but could take-off weighing nearly 66,000lbs.
As a bomber, armament for the P.108 was both defensive and offensive in nature. Her defensive armament consisted of a mix of 12.7mm heavy- and 7.7mm rifle-caliber machine guns in various positions along the fuselage and wings. Unique to the P.108 was its use of remote-controlled 12.7mm Breda-SAFAT heavy machine guns fitted to the rear of her outermost engine nacelles - the thought being that these systems could protect the aircraft's rear from incoming enemy attacks. In theory, this proved a sound measure and other bomber types experimented with such emplacements as well. In practice, however, their usefulness remained to be seen and never effectively utilized by any warplane by war's end. Beyond the wing armament, there was a 1 x 12.7mm machine gun position in the nose, 1 x 7.7mm along each beam waist side and 1 x 12.7mm in a retractable ventral turret at the base of the empennage.
Despite her size, the P.108 's offensive forte was limited to a maximum internal bomb load of up to 7,709lbs across three separated bays. This could be made up of seven heavy-class bombs and up to thirty-eight light-class bombs. Torpedoes would only have been carried by the anti-shipping version (P.108A), two underwing and one held under the fuselage.