Savoia-Marchetti SM.92 Heavy Fighter Prototype
The Savoia-Marchetti SM.92 was an Italian World War 2 attempt at producing a twin-fuselage heavy fighter.
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The conjoining of two airframes to produce an all-new design was a somewhat common occurrence throughout World War 2 (1939-1945) - the Americans and Germans both attempted it through several notable designs. The benefits to such design work was in increased range, firepower and straightline performance though often at the cost of maneuverability, weight and valuable war material. One of the classic examples of this conjoining became the North American F-82 "Twin Mustang" of the United States which mated the bodies of two P-51 fighters along a common central wing mainplane element and tail stabilizer. One of the lesser-known of the conjoined fighter developments of the war became an Italian design - the twin-engine, twin-boom, two-crew Savoia-Marchetti SM.92 - a heavy fighter based on the earlier twin-engine, single-boom, three-crew SM.88 of which only one was built. Like the SM.88, the SM.92 was also only seen in one completed example in 1943 which was destroyed before the end of the war by an Allied air raid.
The SM.92 utilized an asymmetric cockpit arrangement in which the two crew were seated in tandem under a shared canopy within the portside fuselage (as opposed to having two individual cockpits, one in each fuselage as in the F-82). The two crewmen consisted of the pilot and a dedicated rear gunner. Both fuselages included a Daimler-Benz DB 605 series liquid-cooled supercharged inverted V12 engine (1,290 horsepower each) at their front (driving three-bladed propeller assemblies) and vertical rudders at their rear. The two aircraft halves were joined by a common central wing mainplane and a common tail stabilizer plane. The outboard wing mainplanes were symmetrical and held well-forward of midships. The undercarriage was of a "tail-dragger" arrangement with a main leg held under each fuselage section and a single tailwheel fitted under the tail stabilizer unit. Dimensions included a length of 13.7 meters, a wingspan of 18.5 meters and a height of 4.15 meters. Performance from the twin-engine, twin-fuselage arrangement netted a maximum speed of 382 miles per hour, a range out to 1,245 miles and a service ceiling up to 39,360 feet.
In terms of armament for a heavy fighter, the SM.92 was not to disappoint. 2 x 20mm MG 151 cannons (German) were fitted in the central wing mainplane with a third installed in the starboard side fuselage. A single 12.7mm Breda-SAFAT heavy machine gun was installed under each engine with a third fitted to the tail stabilizer unit facing aft (remotely-controlled to engage any trailing interceptors). Beyond its fixed armament, the SM-92 was slated to carry upwards of 4,400 pounds of conventional drop ordnance under the central wing mainplane and an additional 350 pounds under each outboard wing mainplane.
The SM.92 was devised to fulfill an Italian Air Force requirement for a new twin-seat multirole fighter. The wings, tailplanes and boom of the earlier SM.91 were retained for expediency and a twin fuselage, twin-boom planform was used to harness the power of two engines and doubled internal storage space. It was expected that the aircraft would exhibit the required performance of a fighter with the added punch of something more that a traditional fighter could offer. Construction of a flyable prototype was slow and complicated and a first flight was not recorded until October of 1943. Performance was shown to be slower than expected but over twenty hours of flying were recorded through this one example still (though the design was never properly fully vetted). September of 1943 saw the Italians surrender to the Allies but this left the SM.92 in Axis hands nonetheless. In March of 1944, the prototype was engaged by an Axis pilot who mistook the aircraft for an Allied Lockheed P-38 "Lightning" - an American-made fighter which also used a twin-boom configuration but a single, central nacelle for its cockpit placement. While surviving through desperate maneuvering, the prototype was riddled with enough bullets that damage forced it to be grounded for an extended period of time while repairs were enacted.
After this, the sole prototype was lost when Allied bombs were dropped on its holding area - destroying it completely and ending its attempt at fulfilling the Italian Air Force requirement.