Savoia-Marchetti SM.81 "Pipistrello"
Developed as the military version of the SM.73 airliner, the SM.81 prototype flew only 7 months before the SM.79, and was quickly outdated as a day bomber, although remained in service as a transport into the 1950's.
As basically a simplified version of the SM.73, the SM.81 was able to be quickly entered into service and participated successfully in the war in Abyssinia and in Italy's mission to the Spanish civil war. Like most of pre-war Europe, Italy suffered from lack of adequate access to aircraft engines, and so the SM.81 was produced in batches with engines from Alpha Romeo, Piaggio and Gnome-Rhône. The aircraft were otherwise identical and it does not seem that they were given differing marque designators. Not originally planned as such, but the 3 versions became allocated to the 3 theatres of the empire to allow ease of maintenance and logistics. The Piaggio engines were early determined to be best in the hot and high conditions of Abyssinia, and so they became the aircraft of Italian East Africa. The Alpha engines aircraft remained Italian based, and the Gnome-Rhône aircraft became the aircraft of Libya.
The SM.81's were already outdated for Europe by the time Italy entered WWII, and with the arrival into service of the SM.79, they were relegated to night and transport roles.
Like the SM.79, a twin-engined SM.81 bis was flown, the aircraft featuring a similar bombardier's glazed nose. With individual engines of greater power than those of its 3-engined sibling, the total power was less, and so performance was unacceptable to the Italians and no production was ordered. The aircraft was however sold to China for local licence production.