the caproni ca 90 was perhaps one of the
most impressive aircraft designed in the
1920s along with being one of the most
obscure it represented to the
culmination of gianni caproni's
ambitions for building huge imposing
aircraft
from the day he founded his first
company in 1908 caproni always leaned
towards the development of large
aircraft specifically bombers
in world war one he developed several
bomber designs the most numerous of
which was the large and successful ca3
series
after the war he continued to develop
larger and more advanced aircraft as
well as some curious oddities like the
nova plano that we looked at in a
previous video in the mid-1920s caproni
designed the ca-79 which was a sessica
plane bomber the design proved to be a
success though it was not built in
numbers and caproni quickly moved on to
the largest escort plane designs the
next being the ca-80 and the
ca-85 during this period he drew up over
a dozen different designs some were
transports some were passenger liners
and some were bomber designs as well
a few of these designs were amongst the
largest he had conceived up to this
point and indeed a few of them were
amongst some of the largest biplanes
built at the time though they seemed to
have been mostly forgotten by history
the ca79 for example had a wingspan of
33 meters which was larger than all but
two or three other designs at the time
but caproni wanted to push this even
further and designed the largest plane
in the world
the result would be the ca-90 heavy
bomber design work began in the late
1920s with most of the construction
being carried out in 1929 to say this
was a large biplane would be an
understatement
in fact today it remains the largest
land-based biplane ever built
due to the size of the aircraft the
entire framework was based on steel
tubing rather than aluminium or
deraluminium framing and the main joints
were machined from billets of chrome
nickel steel the fuselage was
constructed of square sections and it
also formed an integral part of the
lower wing which unlike most biplane
designs was seated at the top of the
fuselage rather than at the middle or
lower sections
eight cylindrical fuel tanks were housed
in this section along with 11 more in
the nose and four more in a vertical
arrangement behind the bombay the wings
and most of the fuselage half of the
cockpit were clad in fabric and the rest
of the fuselage and the nose was covered
by sheets of corrugated aluminium when
completed the scale of caproni's latest
creation ordered those who saw it in
person
it had a length of 26.9 meters and a
height of 10.8 meters
like many of caproni's recent designs it
was a sesco plane with the upper wing
being smaller than the lower wing
that being said the upper wing was still
huge having a wingspan of 34.9 meters
but it was dwarfed by the lower wing
that had a span of 46.6 meters
the upper wing sat 5.7 meters above the
lower wing and as it was not directly
attached to the fuselage it was
supported by an array of thick struts
and wire bracing
the control surfaces were equally
massive
the ailerons had a span of 22 meters
each the horizontal stabilizer had a
span of 10.2 meters and attached to it
was a pair of 5 meter wide elevators and
a 5 meter tall rudder
as something of this size had not really
been attempted before even more
attention than usual was placed on the
aircraft's flight handling
characteristics for obvious reasons all
parts of the aircraft were subjected to
rigorous tests by the experimental
department of the milan polytechnic
institute
large control servo tabs were fitted to
the rudder and the ailerons which
allowed the pilots to operate the
controls without the effort feeling like
a workout at the gym this combined with
the sensible layout of the cockpit
controls meant that the entire aircraft
could be safely controlled by a single
pilot
speaking of the pilot the ca-90 had an
open cockpit with the controls in a
side-by-side layout this cockpit was
located just before the leading edge of
the lower wing and on each side of the
fuselage below the cockpit was a large
door that granted access to the main
fuselage it is not specifically stated
anywhere how many crew members it had as
a bomber but the design provisioned
seven gunner stations one in the nose
one on the upper wing one in a ventral
gondola two in the upper fuselage and
one on each side of the fuselage none of
the source material indicates that the
defensive armament was actually fitted
to the aircraft but it was expected to
have between 8 and 12 machine guns some
in single mounts and some in pairs
had they been fitted it would have
represented a significant amount of
defensive firepower for this error
a bit more is known about the weight and
payload capacity though when empty the
ca-90 had a weight of 15 tons and it
could carry a useful load of a further
15 tonnes as well giving an approximate
maximum weight total of 30 tonnes
however depending on what safety
standards were adhered to it could
theoretically go up to 35 tons at a
stretch the 15 tons of useful weight
would be made up of fuel people and
bombs all of the bombs were carried in a
bombay behind the cockpit and the bomb
racks could accommodate 850 500 250 and
100 kilogram bombs for a total bomb load
of 8 000 kilograms
now an aircraft of this size and weight
needed a strong undercarriage to support
it and like everything else about the
ca-90 this too was massive with the four
main wheels of the landing gear having a
diameter of two meters
the landing gear had a very wide track
to facilitate landing on rough ground
and the impact was absorbed by
suspension mounted on two struts that
connected the gear to the lower wing and
another pair of struts also connected
the gear to the fuselage itself the
ca-90 was powered by six engines
arranged in tandem pairs earlier on in
his career caproni had subscribed to the
idea that more engines translated to
better safety but after lessons learned
from his eight-engined noviplano and
other designs he realized that too many
engines impaired the safety and
simplicity of an aircraft by increasing
the difficulty of control however in
1929 he would still need more than a few
to lift 30 tons of plane into the air
the engine that caproni selected was the
powerful 57 liter w16 isotopini aso
which gave 1000 horsepower this gave the
aircraft a total power output of 6000
horsepower and is why the aircraft is
also sometimes known as the caproni
6000. one pair of engines was mounted on
each side of the lower wing above the
landing gear strut and the third was
mounted in a central gondola on struts
between the wings the pusher engines
drove a four blade propeller and the
tractor engines drove a two-blade
propeller they were all water-cooled the
front engines had their radiators
mounted behind the propellers and the
rear engines on the wing had radiators
attached to the wing support struts
whilst the central rear engine had its
radiator suspended below the engine
gondola in terms of performance the
ca-90 had a documented top speed of 205
kilometers an hour a landing speed of 90
kilometers an hour and a ceiling of 4
500 meters
though not the fastest aircraft in the
world it was still fast for a biplane of
this size and it could boast an
operational range of 1400 kilometers
whilst carrying an 8 000 kilo bomb load
on the 13th of october 1929 caproni's
giant biplane took off for the first
time flown by test pilot dominico
antonini it was the largest land plane
in the world and almost the largest
plane in general but the dornier do-10
just beat it in total wingspan antonini
immediately praised the aircraft's
handling claiming that the massive plane
had surprisingly light and balanced
controls and that it felt no more
difficult to fly than an ordinary
passenger aircraft he would continue to
fly the ca-90 for all of its tests and
had no difficulty setting multiple load
altitude and endurance records perhaps
the most impressive of these records was
when he got the bomber to carry a 10 000
kilo load at 3 200 meters for three and
a half hours the test flights also
allows caproni to demonstrate the
versatility of his new aircraft though
nominally designed as a bomber it could
easily be converted to a number of
auxiliary rolls removing the bombay
would allow the large fuselage to be
readily adapted for commercial use as a
transport for passengers freight or mail
in this guys it would have an estimated
range of at least 2 000 kilometers and
the aircraft was expected to be capable
of transatlantic flights with the
provision of some additional fuel tanks
this argument was also supported by the
rapid advancements in engine technology
caproni stated that if engines of 1500
or 2000 horsepower became readily
available the aircraft would only need
three or four rather than the six
currently which would of course save
weight and improve efficiency it was
also hoped that the aircraft could cut
into the flying boat market from the
outset the fuselage was designed to be
watertight so that it could be converted
into a seaplane when needed however not
enough documentation exists to expand
much further on this there was a plan
drawn up for the ca-91 which was a
dedicated seaplane and as that design
shared the same wings and engines as the
ca-90 it would be safe to assume it was
a direct result of that line of thinking
after its first flight the aircraft was
considered a technical triumph not only
for italy but for the world of aviation
in general since it demonstrated that
even land planes could reach huge
dimensions without increasing the
difficulty of taking off and landing yet
despite this only one would be built and
it would never see production or
commercial success
the ca-90 was a victim of two things
timing and politics
the current head of the italian air
ministry did not subscribe to caproni's
fondness for heavy bombers
in fact he was not enthused with the
idea of large-scale bombing in general
the idea of heavy bombing was still
relatively young
some people saw it as a gimmick
some viewed it in the same manner as we
view nuclear weapons today a weapon that
should not be used and some thought that
lighter bombers in larger numbers was
the way of the future whatever the
minister's own opinions may have been
caproni knew he wouldn't be able to sell
his plane as a bomber his attempts at
marketing the ca-90 as a commercial
venture were also a failure a proposal
was made to convert it to carry up to
100 passengers over long distance
international routes but the onset of
the great depression put paid to any
consideration of the idea in italy the
same situation unfolded when an attempt
was also made to market the aircraft to
the united states the design was
promising but the money just didn't
exist
and so the largest biplane ever built
would remain a one-off by the time the
world had recovered from the great
depression and the transatlantic roots
were beginning to grow aviation had
moved on to all metal monoplanes and
flying boats
in terms of biplane design nothing of
this scale would ever be attempted again
and despite being the world's largest
biplane the ca-90 was largely forgotten
but like several other large and obscure
planes of recent note it recently
re-entered the public view when it was
depicted in the studio ghibli film the
wind rises
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