Vermillion, to try and answer your questions:
According to a cutaway drawing of the S.M.79-I, the radio operator and flight mechanic sit just behind the cockpit, under the dorsal gun. I assume one of them would operate this weapon. The bomb-aimer uses the bombsight in the gondola, where he also has the ventral gun to operate.
In the drawing there is a single 7.7mm waist gun mounted on a rail that is fired to either side through hatches, one of which can be seen outlined in white in the b&w photo above, above the three lower side windows. The forward gun was fixed, and operated by the pilot.
S.M.79 History.
The S.M.79 was proposed by Alessandro Marchetti in 1934 as a cleaned-up and faster development of his earlier S.M.81 - supposedly to participate in the prestigious 1934 "MacRobertson" race from England to Australia. First flying in October 1934, the S.M.79P wasn't completed in time however, but went on to set several 1000km and 2000km closed circuit world records. Among their many racing acheivements, S.M.79's claimed the first three places in the 1937 Istres-Damascus-Paris race.
After the S.M.79P, 5 S.M.79C(orsa) racers and 11 S.M.79T(ransatlantica) long range commercial transports were completed with 1000hp Piaggio P.XI RC.40 radials, and work began on the S.M.79B - a twin engine comercial transport version.
The S.M.79B failed to gain interest as a commercial aircraft, but was sold as a military aircraft to Iraq(4) and Brazil(3) equipped with 1030hp Fiat A.80 radials.
Romania purchased 24 S.M.79B with 1000hp Gnome-Rhone radials, and later another 24 with 1220hp Jumo 211Da inlines. Romania also arranged to license-build their own version of the S.M.79B as the S.M.79-JR at the IAR factory in Bucharest. These aircraft had top speed 277mph at 16400ft, climb to 9845ft in 8:40, and ceiling 24280ft.
The S.M.79 entered service with the Regia Aeronautica in 1936 as the S.M.79-I with three 780hp Alfa Romeo 126 RC.34 radials.
In 1937 trials had begun with torpedo installations on the S.M.79-I, at the same time more powerful engines were fitted, resulting in the S.M.79-II with 1000hp Piaggio P.XI RC.40 radials and the ability to carry 2 torpedoes(although usually only 1 was carried).
In late 1943 small numbers of the S.M.79-III appeared, powered by 1350hp Alfa Romeo 135 RC.32 radials. The ventral gondola and bombsight were removed, and the forward machinegun was replaced with a 20mm cannon.
Apparently there was also a system of ethyl injection used with the Alfa Romeo 128 RC.18 engine, which boosted the top speed to over 298mph, but also led to large numbers of unserviceable engines causing the grounding of most of the S.M.79 still in service by the time of the invasion of Sicily.
In total, 1330 S.M.79 were produced in Italy between 1934 and 1944.
Source: Bombers of World War II ISBN: 1-84013-149-7 (The book is a 1998 compilation of material previously published in the Airplane reference set of magazines.)
[This message has been edited by juzz (edited 07-28-2000).]
