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

An Alfa-Romeo-engined S.M .81 o f the 202° Squadriglia inflight: this unit took port in the occupation o f Albania, flying transport and night bombing missions from Valona. (Photo: Heinz J. Nowarra) The Savoia Marchetti S.M .81 There is no doubt that General Franco's Nationalist movement in Spain was saved from early extinction largely by nine tri-motor aircraft the S.M.81 bombers which on 30th July 1936 flew from Elmas in Sardinia to Melilla in Spanish Morocco, under the command of Commondante Bonomi, and assisted in the transfer from Centa to Algeciras of the units of Spanish colonial troops without which the Nationalist insurrection would have lost its impetus and become ineffective. Almost contemporary with the S.M.79 (see Profile No. 89), the S.M.81 appeared in 1934 as a military development of the S.M.73 tri-motor transport, and was immediately put into series production in order to buildup the medium bomber strength of the Regia Aeronautica it remained the standard Italian bomber until the greatly superior S.M.79 began to enter squadron service in 1937. Production was carried out on a large scale and involved, apart from the parent company, almost every aviation plant in Italy Piaggio and CM ASA produced complete airframes. To achieve the greatest possible reliability and versatility in service, the aircraft was conceived in several versions powered by different types of engines. The four main variants were powered by the 650 h.p. Alfa Romeo 125 RC.35 the 680 h.p. Alfa Romeo 126 RC.34 the 670 h.p. Piaggio P.X RC.35 and the 650 h.p. Gnome-Rhone K.14. Consequent to the variation in powerplant, three distinct types of engine cowlings were employed an initial short- chord Townend ring was followed by a similar type of longer chord, and this was finally replaced by a smoother, tapered Magni-NACA cowling. It is known, however, that the prototype and some of the pre-production aircraft were powered by Piaggio P.IX RC.40 engines with four-bladcd propellers and undercarriages of smaller wheel-base at that stage the armament layout had not been finalised and the fuselage windows difiered in configuration from those of series machines. Inmost cases the propellers were subsequently replaced by standard three-blade instal­lations. THE S.M.81 DESCRIBED When it appeared, the S.M.8I represented a high standard of complexity for its time it also presented the most serious challenge to date for the well-known Centro Sperimentale at Guidonia. The prototype and the pre-series machines were subjected to a tight schedule of severe tests, including a trials programme involving the mounting of two torpedoes these latter were not particularly successful. The aircraft was of mixed construction the cantilever wing of wooden structure was built upon three double-T section main spars and in three sections, the centrc-section being integral with the fuselage. For emergency floatation, 36 water-tight compartments were built into the structure, as with 3
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