Savoia - Marchetti SM . 78 The Savoia - Marchetti SM . 78 was an Italian bomber / reconnaissance biplane flying boat of the early 1930s . Development . The SM . 78 first flew at the end of 1932 , designed for the role of maritime reconnaissance - bomber . It was one of the many flying boats made by SIAI ( Savoia - Marchetti ) , that in 1915 had started building foreign aircraft under licence , followed two years later by the first of its own designs . The SM . 78 was developed from the SM . 62 bis . The prototype , which carried the serial number " MM222 " , made its first flight late in 1932 and then transferred the next year to Vigna di Valle for evaluation . The SM . 78 was the last biplane flying boat , built or used in large numbers by Italy ; 49 were completed in all ( 32 by Piaggio and 17 by SIAI ) . Technical description . The SM . 78 was a single - bay biplane . It had a long and slim aft fuselage , with a tall welded steel fin and a wooden horizontal tail mounted centrally . The lower hull had two steps , to aid take - off from the sea . This aircraft evolved from the SM . 62bis , retaining practically the same unmodified wings , tail and fuselage , but with a different model of Handley Page flaps . The hull / fuselage had poplar frames , and longerons made of ash . The plywood - skinned hull had a double - layered bottom , with an external layer of cedar , while the flanks were made from orthogonal ly arranged laminates of cedar . The fabric - covered wings had spruce longerons and poplar ribs , utilising the low - weight and high - strength characteristics of these woods , and were painted to render them impermeable to water . Twin stabilising floats were mounted at mid - wing . While the pilot and co - pilot were seated side - by - side in an enclosed cockpit in the prototype , this was replaced by an open cockpit in the production model . A crew position mounting a 7 . 7 mm ( 0 . 303 in ) Lewis Gun was situated in the nose , which also contained two cameras . This position was manned by the co - pilot when necessary , the aircraft having a three - man crew . A second , enclosed turret was fitted in the dorsal position , also armed with a 7 . 7 mm ( . 303 in ) Lewis gun , manned by the gunner / radio operator , who was also provided with an R . A . 350 transmitter and an A . R . 4 receiver . The aircraft was not fitted with an intercom , but the two pilots could communicate with the nose position using a " pneumatic message " system in which messages were passed through a tube . The forward machine gun had 564 rounds of ammunition in 12 magazines , while the aft machine gun had 470 in 10 magazines . Bombs were carried in a bomb bay within the lower wing , near to the fuselage . The weapon - load was 700 kg ( 1 , 540 lb ) maximum . Typical combinations were : 2 × 250 kg ( 550 lb ) and 2 × 100 kg ( 220 lb ) bombs , 6 × 100 kg ( 220 lb ) bombs , 4 × 70 kg ( 150 lb ) depth charge s , or 6 × 12 kg ( 26 lb ) training bombs . Smoke generators could also be mounted on the inner hardpoints . A " " Jozza " " bombsight was located on the right in the cockpit , behind a glazed window . The aircraft was powered by a single Isotta Fraschini Asso 750 W18 engine , generating 671 kW ( 900 hp ) at takeoff , arranged in a steel structure mounted between the two wings , driving a four - bladed propeller with variable pitch that could be set before takeoff . This , and the much refined hull of this aircraft bestowed a good performance for the time . A CO² fire extinguisher was mounted by the engine . A total of 2 , 200 L ( 580 US gal ) of fuel could be carried in six unarmoured duralumin fuselage tanks , two aft , two central and two forward . Operational history . The SM . 78 was built between 1932 and 1935 , with only 16 by SIAI and 32 from Piaggio . It equipped the 141° " Squadriglia " , based at La Spezia , the 144° based at Livorno , the 182° at Nisida and the 189° at Syracuse . It continued to serve until 1938 , being replaced by the CANT Z . 501 , a monoplane design with superior performance . Some aircraft remained in service during the early phase of World War II , performing in an air - sea - rescue capacity . Spain , which already operated SM . 62s , tried unsuccessfully to acquire a licence to build the SM . 78 , leaving Italy as the only operator .