Hello, and welcome to Aviation Deep Dive. It’s the 1930s, and across the world advancements
in aerodynamics, hydrodynamics, and engine power are allowing aircraft to become bigger
and better. Seaplanes too, are entering their golden age,
getting to the size of ships and carrying passengers all around the world in luxury
akin to a cruise ship. The aircraft that we’re looking at today,
borne of this era, is rather interestingly, the largest floatplane of all time! Heralding from Italy, sporting 4 radial engines
and being almost 30 metres, or 100 feet, long - today we’ll be taking a look at the history
of the CANT Z.511. Italy had initially been late to the civil
aviation sector, and didn’t really try its hand at serious native design or production
until the 1920s. Having said that, once they did, their aviation
industry bloomed, making leaps and bounds technologically, and producing some really
excellent aircraft. In 1933 and 1934 the Macchi M.C.72 set the
world speed record for any aircraft, its 1934 record still makes it the fastest piston engine
powered seaplane of all time, reaching 709 km/h! The CANT Z.506, produced just three years
later, would go down in history as one of the best military seaplane ever produced - Italy
was certainly making a name for itself in the sphere of hydroplanes. As such, in mid-1937 the civil aviation company
“Compagnia Ala Littoria” issued a specification to the now centralised Italian aviation industry. They wanted a long-range seaplane that would
be capable of carrying a large number of passengers and cargo on transatlantic routes to Latin
America. CANT, otherwise known as the Trieste Shipbuilding
and Naval Aeronautics company, immediately accepted the specification and began design
of an aircraft to meet the specification. Between September 29th and October 1st 1937,
Filippo Zappata, chief of design, sketched out a design for the largest floatplane in
the world. Four-engined, fast, and with a very promising
design on paper. By December 1939, the construction of the
first Z.511 prototype was almost complete, with the second just behind. But the program had hit a roadblock, to do
with the engine that had been originally intended to power the aircraft. The Alfa Romeo 135 was a twin-row 18 cylinder
radial engine, that could produce an incredible 1,600 horsepower at full power - and though
it had certainly looked a promising powerplant for the project in 1935, four years later
the engine was still nowhere near reliable enough for operational use - it routinely
broke its camshaft and had significant general issues. Despite its technical problems however, the
Alfa Romeo 135 was actually so promising, boasting such a high power output, that the
Luftwaffe bought some in 1944 for testing on Focke-Wulf Fw 200 Condors, but that’s
a story for another day. Regardless, they were certainly not in a good
enough state to power the Z.511 in 1939, so the designers had to look elsewhere for a
suitable powerplant. Looking across the Atlantic, they were apparently
taken by the US built Wright R-2600 Twin Cyclone, which matched the power output of the Alfa
Romeo engine but was far more reliable. CANT lodged a request with the authorities
to ask permission to order six of these engines, but due to deteriorating relations they were
unable to secure the order. As such, the flight tests were delayed for
a further year until 1940, until finally the company was able to secure some Piaggio P.XII
RC.35 18-cylinder radials. These had the advantage of being home-grown,
but they were a far cry from the Wright Cyclones. Their power output was good, at 1,500 horsepower,
but they suffered from poor reliability and were generally considered a worse alternative. Regardless, it was the only engine suitably
powerful that the Italians could muster, so it was fitted to the first prototype, finally
completing the aircraft. Standing at 11 metres tall, 28.5 metres in
length and 40 metres in span, the CANT Z.511 was by far the largest floatplane ever constructed
by this point - even just one of its enormous pontoons was almost 20 metres long - about
as long as a B-17. Sporting a very beautiful, streamlined look,
the aircraft was of all-metal construction. The wings, in fact, would be so tall that
there was a space in the leading edges tall enough for a man to walk through, who could
service the engines and fuel tanks during flight. The majority of the fuel would be kept in
the wing tanks, with a smaller auxiliary fuselage tank, for a total fuel capacity of 16,340
litres, or 4,340 US gallons. A crew of Now ready for flight tests, the Z.511 was
moved to Monfalcone, in Northern Italy. And in October 1940, the month the Italians
would begin their invasion of Greece, the Z.511 took to the skies, piloted by Mario
Stoppani. The aircrafts designer, Zappata, was also
on-board - but the first flight would not be an easy one! Almost immediately having taken off, the Z.511
was taken off course by an extremely strong gust of wind, and it was found that the ailerons
were completely unresponsive. In a very risky situation, the officials on
the round watched as the enormous Italian floatplane flew off, at the mercy of the winds
and only being able to steer a little with the rudder. Stoppani, the pilot, was very skilfully able
to bring the aircraft in an enormous circuit using the differential thrust of the engines
and the rudder to turn, and eventually made it back to the lake for a safe landing. It transpired that the rods which connected
the control stick to the ailerons had apparently become wet and thus expanded, meaning there
was a huge amount of slack in the rod. Zappata, presumably rather shaken by this
encounter, immediately set about redesigning the control system in the wings, replacing
the elastic pulleys with rigid rods - the whole ordeal took about 3 months to complete. Following this, the Z.511 continued undergoing
flight testing, at various loads and in different conditions - on one flight the aircraft made
a very intense landing at sea with six foot waves and 40 mph winds - the engineer was
sure that the floats would collapse or simply be destroyed from the stress. But the aircraft took the pounding from the
waves, and was even able to take off again - not to mention that at the time the aircraft
had been at its fully loaded weight of 34,000 kg or 75,000 lbs. This proved the structural integrity of the
aircraft beyond question, it was incredibly ruggedly built, for context most floatplanes
are limited to landing in swell no higher than 12 inches, or 30 centimetres - this was
6x that! The speed of the aircraft also ended up being
fairly respectable, using it’s combined 6,000 horsepower to achieve a maximum speed
of 424 km/h at 3,500 metres, and Overall, testing was certainly considered
to be a success, but by this time it was already mid-1942, and interest was rapidly dwindling
away from civilian aircraft - Italy wanted designs that could function in a military
application. The second prototype had been disassembled
to make space in CANTs workshops for other projects, and in order to appease Italian
officials, and possibly secure some actual orders for the aircraft, a military conversion
of the Z.511 began to be explored. It was considered that due to it’s enormous
size and range, it could be well-suited to the Maritime patrol role - it could be fitted
with racks to carry ordnance on the outer wings, as well as internal bomb bay and leave
lots of space, and available weight, for defensive armament. And defensive armament was indeed suggested! In the form of no less than 10 single mount
12.7mm BREDA machine guns in both side positions, two dorsal turrets, and belly positions - furthermore
a 20mm MG 151 would be mounted in the glazed nose - making this an extraordinarily well-defended
aircraft, one of the most heavily armed aircraft of the war! Aside from guns, however, the aircraft would
carry up to 4,000 lbs of bombs or torpedoes - to be put to use against any enemy ships
it came across in its 15 hours of endurance. An interesting feature of the Z.511, is that
it would have been able to carry up to four 533 mm torpedoes, which is actually more than
any other ww2 aircraft I know. It’s interesting to note that although its
military conversion program ultimately came to nothing, it could feasibly have replaced
Fw.200 Condors - as the two types have a fair amount of similarities, at least superficially. Both converted from airliners into maritime
patrol bombers, the Z.511 is basically just better in every aspect, its payload, speed,
defensive armament and even range could be better, provided it got some extra tanks. The Z.511 was also incredibly strong, as we’ve
discovered, whereas the Condor was always plagued by structural issues that stemmed
from its ill-suited conversion to carry a lot of heavy equipment, its back would often
‘break’ on landing. Anyway - Desperate to find a use for the Z.511,
it was suggested in roles such as a troop transport to fly groups of Italian saboteurs
into important enemy sectors, as well as in a transatlantic crossing to Latin America. Even using it on solo strike missions to target
fuel warehouses in the Persian Gulf or Soviet vessels in the Black Sea were considered,
as well as an idea to fit it with a midget submarine that would be flown in and dropped
deep into enemy waters - but ultimately the finished prototype stayed moored at its lake
in Northern Italy, whilst the half-built one stayed mostly disassembled in its facility. The Z.511 took its last flight in September
1943, and was just days later strafed by marauding British fighters on the lake, which caused
serious damage, although it did stay afloat. Transferred to Vigna de Valle for repairs,
by this time the Allies had invaded and were sweeping across Southern Italy, and the workers
at the base apparently did not want it to fall into either Allied or German hands - sabotaging
and destroying the aircraft. The other Z.511, still half-built, was seized
by German forces and scrapped for metals - thus bringing a sudden end to the only two Z.511s
in existence. This aircraft has remained shrouded in mystery,
far more mysterious than anything of its size should be. For this video, I was only able to find a
handful of pictures, and references to in books are few and far between, any detail
is exceedingly rare, and I’ve had to gauge most of it from secondhand accounts from historians
that have visited Italian archives. Nevertheless, the Z.511 is certainly deserving
of attention, as it was no doubt a pretty incredible aircraft. Brainchild of the legendary aeronautical engineer
Filippo Zappata, the Z.511 proved itself to be rugged, reliable, fairly fast and high
capacity aircraft - and one that would simply never really catch on due to the fact that
it’s development coincided with its intended passenger route being cut off, after the outbreak
of war. Unfortunately fate wasn’t kind to the legacy
of this aircraft, and both were completely destroyed, and we’re only left with images
and blueprints to remember this extraordinary aircraft by. A huge thanks to my Patrons, on screen now,
for supporting the channel and Thankyou so much for watching this video of Aviation Deep
Dive. Consider liking and subscribing for more weekly
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