In 1939 Ing. Filippo Zappata designed the four-engine Z.511 transatlantic passenger airliner.
Originally intended for Alitalia's South Atlantic route, the Z.511 featured a two-level fuselage
with crew and passenger compartments above, and mail and freight holds below. Sleeping accommodations
for sixteen persons were to be provided. However, the prototype was not completed until after the outbreak
of the war, flying for the first time in September, 1943. Another example was built concurrently. An
excellent and rugged design, the Z.511 could moor on waves nearly seven feet high with little adverse effect, and
had a maximum range of 2796 miles.
An ambitious plan for raiding New York harbor was under study in 1943 by the Regia Marina, using "Porcellini" man-guided
torpedoes, already successfully employed against the British, sinking the battleships Valiant and Queen Elizabeth at Alexandria.
The two Z.511 seaplanes were to fly the Atlantic, taxying in under radar screen to a point from which the manned torpedoes
could be launched. No provisions were made for retrieving the naval personnel after their attack. Before this project
could be realized, the two Z.511s were damaged beyond repair at Lake Trasimeno by strafing Allied aircraft.
The military Z.511A was powered by four 1500 hp Piaggio P.XII RC.35 radial engines giving a maximum speed of 264 mph,
a cruising speed of 205 mph and an alighting speed of 84 mph. It could climb to 13,120 ft in 16 minutes. Empty and loaded weights
were 45,012 lb and 73,830 lb respectively. Span was 131 ft. 2 1/2 in., length was 93 ft. 6 in., height 36 ft. 1 in., and wing area 2098 sq ft.