Profile Publications No. 146 The Savoia Marchetti S.M.81

The prototype S.M .81 inflight. (Unless otherwise stated, all photographs in this Profile are from the author's collection). One o f the pre-series aircraft, showing details o f the homb- aimer's position and the open-sided wheel fairings. The engines were Piaggio P.IX R.CAO's with narrow-chord Townend rings. the civil S.M.73. The ailerons were of tubular steel with doped fabric skinning, and the flaps (maximum angle 38 )were of modern design, offering low-speed performance. The fuselage was of welded chrome- molybdenum steel tubular structure, with a mixed aluminium and fabric skin. The structure was made in two sections the main section from wing-root to tail and the secondary section including the cockpit and central engine housing. The cockpit accom­modated two pilots seated side by side, with a further crew of three bomb-aimer, engineer, and radio operator. A glazed bomb-aimer’s gondola was provided under the fuselage immediately aft of the central engine nacelle armament included two semi-retractable hydraulically operated turrets in dorsal and ventral positions, each mounting two An S.M .81 with Gnome-Rhdne K .I4 engines. 7-7 mm. machine guns. A fifth hand-held machine gun could be fired from either one of two beam hatches. The normal bomb-load was 2,640 lbs. (maximum 4,400 lbs.) stored vertically in the bottom of the fuselage. This method of bomb storage did not allow a predictable bomb trajectory, which partly explains the mediocre results often obtained by Italian bombers. Typical loads were four 1,100 lb. or 550 lb. bombs sixteen 220 lb. bombs twenty-eight 110 lb. bombs or fifty-six 44 lb. or 33 lb. weapons. Because of the low reliability displayed by the 7-7 mm. guns, many wartime S.M.8I’s were fitted with a Lanciani Delta turret amounting single 12-7 mm. Safat gun. The radio and electrical system was a standard type with a single battery and two main circuits. The radio equipment included an RA 350 transmitter, an AR 5 receiver and two P 63 radio compasses. The tail unit was constructed of welded chrome- molybdenum steel tubular framework with fabric covering the tailplane was of variable incidence, with external bracing and a rudder servo tab. The under­carriage consisted of two independent spatted elements with a split axle. The three engines were fitted on steel tubular mountings with four attachment points the cowlings varied as described above. The fuel system comprised eight tanks Piaggio and Alfa Romeo-powered machines had a total capacity of 795 Imp. gallons, while those powered by Gnome- Rhone engines carried 968 Imp. gallons. Six tanks were built into the wing centre-section and two in the wing outboard sections. The three oil tanks had a total capacity of 49 Imp. gallons. The three airscrews had a diameter of 11-15 ft. (Piaggio, Gnome-Rhone) and 11-48 ft. (Alfa Romeo). A twin-engined version designated S.M.81 bis was developed with two 840 h.p. Isotta Fraschini Asso XI RC twelve-cylinder Vee engines and a glazed bomb-aimer position in the nose. This arrangement would seem to have offered the best operational layout for crew and bomb-load, but it was not sufficiently successful to justify production. Empty and loaded weights of this version were 14,960 and 22,800 lb. respectively the length was 58 ft. 81 ins. Performance included a maximum speed of 204 m.p.h., a cruising speed of 186 m.p.h., a service ceiling of 26.240 ft. and a range of 1.336 miles. 4
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