four machine guns as defensive weapons, but almost completely lacked protective armour. The reasons for the Sparvieros success lay in its flying characteristics. The Sparviero was a more difficult aircraft to fly with a heavier wingload, but overall its three engines provided more power than the twin-engine arrangement of the BR.20. The Sparviero, weighing around the same, had a reserve of power and was capable of performing acrobatic manoeuvers, even rolls. Its engines were more reliable than those of the BR.20 and had enough power to return to base even with one shut down. The Sparvieros superior agility enabled it to perform as a torpedo-bomber, while the Cicogna was never considered for that role. Over 1,200 Sparvieros were constructed, being at least twice as many as the Cicogna. Further development Upon its introduction, the BR.20 was a cutting-edge aircraft and benefited from an overall good design, however, the bomber quickly became obsolete in the face of rapid advances made in the field during this era. The scarcity of improved versions of the aircraft condemned the BR.20 to be only viable in the role of a second-line machine, being underpowered and lacking in defensive firepower by the outbreak of the Second World War. By the time Italy had entered the Second World War, a new variant of the bomber, designated as the BR.20M, had been produced and put in service. The improved BR.20M featured a different nose provisioned with additional glazed sections for the bombardier, along with a slightly longer fuselage. Also, the weight was increased because a part of the fabric was substituted with metal, improving the resistance to flutter and vibration from the engines while reducing speed from 430 km/h (270 mph) to 410 km/h (260 mph). The final production variant was the BR.20bis, which was effectively a complete redesign of the aircraft. It featured a fully glazed nose, a retractable tail wheel, and more streamlined fuselage, pointed fins, although the principal change involved was increased engine power from a pair of 932 kW (1,250 hp) Fiat A.82 RC 42 radial engines, along with an improved and heavier armament. The nose held a simple machine gun position rather than the turret used on earlier aircraft and two waist blisters were fitted over the wing trailing edge while the dorsal turret was a Breda Type V instead of the earlier Caproni Lanciani type. The BR.20bis was considered to be an