The Italian Air Force ("Regia Aeronautica") was one of the few air national powers of World War 2 (1939-1945) to employ the tri-motor aircraft arrangement in number and this was embodied through its mixed medium bomber fleet of Savoia-Marchetti SM.79 Sparviero ("Sparrowhawk"), Fiat B.R.20 Cicogna ("Stork") and CANT Z.1007 Alcione ("Kingfisher") offerings. In the latter design, the record-setting Z.506 "Airone" floatplane served as the basis for what evolved into a land-based variant - both of these designed by CANT engineer Filippo Zappata (1894-1994). The Z.1007 appeared, in its serviceable form, in 1938 and would see production reach approximately 540 examples (sources vary slightly) by the end of the war with manufacture spanning 1938-1943. It was considered one of the better Italian medium bombers of the war though not without some inherent design issues brought about by practical use.
Zappata began with two seperate medium bomber designs under the Z.1007 and Z.1011 designations. These were to feature wood construction and power served from 3 x Isotta-Fraschini Asso XI RC.15 liquid-cooled, inline piston engines driving two-blade metal propellers. The Z.1007 became the favored design to which an order for eighteen was placed in January of 1936. An additional sixteen then followed on February of 1937.
It was not until March 11th, 1937 that a prototype of the design actually flew though performance results were less than expected. The engines failed to meet their listed 840 horsepower output and proved unreliable. This prompted modifications to the base design included use of three-bladed propellers and the introduction of annular radiators at each engine. Production of first-batch models matched this prototype and evaluations were handled by the 16th "Stormo" out of Vicenza - the Z.1007 found to be largely inadequate for military service. Its defensive armament consisted of just two machine guns - 1 x 12.7mm Breda-SAFAT heavy machine gun in an open-air dorsal mounting and 1 x 7.7mm medium machine gun at a rear ventral position and its total bomb load was 1,760lbs.
What followed was a nearly complete revision of the Z.1007 to emerge as the "Z.1007bis" and Zappata took the time to address several concerns noted in his original design. Dimensions were completely enlarged including wingspan and cross-section which added surface area and weight while presenting more drag and lift as well as additional internal volume for the crew, fuel and weapons. Defensive machine gun positions were added and existing gunner positions were modified with better firing arcs. Machine guns now numbered 2 x 12.7mm heavy machine guns and 2 x 7.7mm medium machine guns. One machine gun post sat in a manually-powered turret on the fuselage spine which offered the best firing arcs. The ventral position was retained though upgraded to a 12.7mm machine gun. Beam positions were added for side-facing defense, each mounting a 7.7mm machine gun. The complete crew complement numbered five - two pilots, a bombardier/navigator, dorsal gunner and radio operator.
One of the key changes to the Z.1007bis design was its selection of 3 x Piaggio P.XI RC.40 14-cylinder radial piston engines of 1,000 horsepower (each). In a three-engined configuration, this would provide the airframe with the necessary power the Italian Air Ministry sought of its new medium bomber. In general, radial engines were also less complex, requiring simple air-cooling, as opposed to a complex liquid-cooling arrangement found in inline types. If damaged in the slightest, inline engines held the higher propensity to fail in combat when compared to radials.
The Z.1007bis retained the general shape of the original Z.1007 with its low-set monoplane wing arrangement. The cockpit was of a slim design, promoting an aerodynamically efficient profile though forcing the two pilots to be seated in tandem. A passageway was set to their right to allow crew to access the front and rear portions of the aircraft in-flight (the bombardier's position was at the lower front end of the fuselage). The fuselage was well-streamlined from nose to tail, considerably tapered heading aft. The cockpit appeared in stepped form from the fuselage spine and covered over in a heavily glazed structural arrangement. Its position in the configuration offered generally good views of the action around the aircraft including views to the side engines. The undercarriage included two single-wheeled main legs at each wing engine nacelle and a small tail wheel at the rear. The tri-motor approach offered the Z.1007 its unique appearance, with an engine seated at the leading edge of each wing. The third was fitted to the nose of the fuselage to complete the arrangement.
In and of themselves, the three-engine arrangement did not produce 3,000 horsepower as may be expected of such a grouping. In total output, the arrangement was rather low-powered for its perceived strengths, more equivalent to a two-engined design outputting no more than 1,500 horsepower. The power offered by the 3 x Piaggio engines allowed for a maximum speed of 285 miles per hour, a cruising speed of 210 miles per hour, a range of 1,120 miles and a service ceiling nearing 27,600 feet.
The Z.1007bis featured an internal bomb load now improved to 2,430lbs. An additional 2,200lbs could be carried externally under the wings which increased the total bomb load to nearly 5,000lbs. In lieu of conventional drop bombs, the Z.100bis variant was cleared to carry 2 x 1,800lb torpedoes for the maritime strike/anti-ship role though it is understood that no Z.1007s were ever fielded as such.
The Z.1007bis emerged in late-1938 and became the definitive Z.1007 mark seeing the most production of the entire line. Eight pre-production forms served as evaluation testbeds over Guidonia. During testing, longitudinal instability was present and this led to a revised version of the single rudder tail now featuring a split, twin vertical fin design. During operational service, both forms saw action and a total of 450 of the Z.1007bis variant were produced.
The Z.1007 production line came to a close with the final form - the Z.1007ter. This variant debuted in the early part of 1943 - before the Italian surrender of September - and was outfitted with 3 x Piaggio P.XIX radial piston engines. The new design sported a maximum speed of 305 miles per hour and a service ceiling of 32,900 feet. Production of this type was limited to just 50 examples.
Z.1007 Operational Service
The Z.1007 was formally operational in the spring of 1940 and featured in the 47th Stormo groups of the 106th and 107th. When Italy entered World War 2 in June, these were not deemed combat worthy which limited their initial value. Z.1007s were used by Italy during the Siege of Malta (June 1940 - November 1942) in an attempt to claim the island as a staging post for ongoing Axis control of Northern Africa. It was used in the night bombing role as well though less than half of the available thirty aircraft were actually of useful service in the campaign. The campaign ended as a decisive Allied victory and a blow to Axis operations in the Mediterranean.
Italy delivered just three Z.1007s to Axis-controlled Belgium during the German campaign to take Britain in the Battle of Britain (July - October 1940). Intended for reconnaissance, the aircraft were longer needed by the time of their arrival in September and only served in one forgettable mission - though it incurred no losses.
It was during the Italian invasion of Greece that the Z.1007 was to show its worth. The invasion began on October 28th, 1940 with Z.1007s pressed into action and the bombing campaign completed what would become the largest-scale use of the Z.1007 in all of World War 2. However, the Greco-Italian theater also unveiled a key flaw to the Z.1007 design - its wooden structure - which proved highly influenced by environmental factors. The humidity and rains of the region during the conflict led to warping of the structure and generally limited its availability during key phases.
Despite this, the Z.1007 was kept in play for lack of better alternatives and its availability. This then led to its use over Yugoslavia beginning in early April 1941. The short-lived Yugoslavian Front lasted from April 6th until April 18th and led to a decisive Axis victory. The Italians made up a force led by the Germans and aided by Hungarian elements.
From this point onwards, the Z.1007 was kept mainly in operations around the Mediterranean to help govern control of vital shipping lanes. It also assisted in actions across North and East Africa while its service along the East Front proved short - this, again, due to environmental extremes, particularly over Soviet territory. In September of 1943, the Italian government signed an Armistice with the Allies which removed them as an Axis supporter for the duration of the war. In their retreat northwards, the Germans took control of some thirty Z.1007s though never made use of them in combat. Remaining stocks fell to the re-established Italian Air Force (the "Italian Co-Belligerent Air Force") now fighting against the Axis.