Today we’re looking at the CANT Z.501, a plane whose history included breaking records,
and the unplanned removal of the occasional limb. In the early 1930s the Italian Air Ministry was
looking for a replacement for the Savoia Marchetti S.59, which was at the time
their main reconnaissance flying boat. It had only been in service since 1926, but the rapid
march of progress was making it obsolete, and by 1933 it was thoroughly outclassed.
An attempt had been made in 1930 to secure a replacement, but this had yielded little results,
and the air ministry had been forced to use a substitute in the meantime– the Caproni Ca
111. However, this was not ideally suited to the maritime needs of the Regia Aeronautica,
being chiefly designed as a landplane, and so in 1933 the Air Ministry penned a fresh requirement
for a long-range maritime reconnaissance plane. The aircraft needed to have a top speed of 350
kilometres per hour at 1500 meters, it had to be able to carry a useful payload in the
form of bombs or depth charges for light bombing duties, and its dimensions could
not exceed those that could be accommodated by the existing suite of seaplane hangars,
which meant an overall wingspan and height no greater than 22.5 and 5.5 meters respectively.
This specification resulted in two design submissions, the Savoia Marchetti S.78,
which would incidentally become the last floatplane developed by the company before they
shifted focus to landplanes, and the CANT Z.501. For those who are unaware, CANT is an abbreviation
for the Cantieri Aeronautici e Navali Triestini company – which translates to
Trieste Shipbuilding and Naval Aeronautics. Though they had some experience in producing
seaplane designs, this would only be CANT’s second aircraft built for naval aviation
rather than civil use, the first being the catapult launched CANT 25.
The 501 would also be the first aircraft designed after the company went through a major
re-organisation in 1931, which saw the return to Italy of aircraft designer Filippo Zapata
at the request of Italian Air Marshal Italo Balbo. Zapata was immediately installed as CANT’s
chief designer, and within just a few months a very peculiar aircraft began to take shape.
Zapata was well known for designs that were a bit different, often thinking outside the box,
and the Z501 was no exception. At first glance it is best described
as a tailless monoplane that had a wingless seaplane suspended beneath it…because really,
that’s what it was. Officially, it was defined as a high-wing parasol monoplane, though this is
taking the concept to somewhat lofty extremes. Despite looking very odd, and despite just
fitting inside the assigned hangar with a wingspan of 22.5 meters, the
Z501 Prototype began to capture the attention of the military before it had even been completed.
As with his previous works, Zapata had gone for a highly streamlined aircraft constructed mostly of
wood and covered in fabric. The braced wing was supported by a series of struts that connected it
to the sides and the top of the fuselage, and pair of floats – which were attached to
both the wing and the fuselage – were designed to keep the aircraft stable on the water.
The engine, along with a position for a defensive gunner, was mounted in a nacelle within the wing,
but despite the outward appearance, the engine installed was not a radial engine. It was in fact
an experimental 750hp, inline Isotta-Fraschini that made use of a new circular radiator which
gave it the appearance of a radial. The crew compliment consisted of four: two pilots,
one engineer, and a radio operator. Defensive armament included three 303 calibre machine guns,
one in the upper nacelle, one in the nose, and one in the centre of the fuselage,
and the aircraft could carry up to 640 kg of bombs underneath the wings, and these could
also later on be substituted for depth charges. The prototype flew for the first time on the
7th of February 1934 with chief test pilot Mario Stopanni at the controls.
During its initial trials, it became clear that the aircraft could not achieve anything like the
expected top speed of 350 kmh, topping out at a mere 275, but this disappointment was quickly
offset by the aircraft’s surprising capability for endurance and range.
Additionally, though it was slower than expected, the Z501 was still faster than
many of its contemporaries, such as the Dornier Do 18 and the Saunders Roe London,
and so after weighing up these facts, and after deciding that range was better than
speed for maritime reconnaissance, the decision was made to order the aircraft into production.
It was also decided to use the 501 as a new record-setting aircraft,
as Italo Balbo had a hunger for further expanding Italian prestige in the field of aviation.
This continued a trend which had been set by Balbo’s trans-Atlantic crossings in
Savoia Marchetti S55s, as well as numerous speed records that had been set by various pilots.
In September 1934, the Z501 prototype was made ready for an attempt to beat
the straight-line distance record set by a seaplane,
a record currently held by the United States, who had flown 3862kmh in a Consolidated P2Y.
It broke the record on the 18th and 19th of October, flown by a crew of three that
included test pilot Mario Stoppani. The chosen route covered 4130 km between
Northern Italy and Eritrea in a flight that lasted approximately 26-and-a-half hours.
The record, and subsequent media attention it garnered, was short lived, as the French then beat
it again in June of 1935. This, of course, was not allowed to stand and the prototype was hastily
modified for another record-setting flight in July. Now fitted with a variable-pitch propeller,
it took off on the 16th of July, flying from Northern Italy to British Somaliland,
and covering 4930km in approximately 25 hours. These record setting events led to more orders
for the Z501 from the Regia Aeronautica, and their large production run contributed
to a fairly long service life…though other factors were also at play.
The production model featured a few differences from the record-setting prototype.
One change was the installation of two Vickers-style gunner stations, one on the engine
nacelle and the other in the central fuselage, these being equipped with Lewis machine guns.
The split glazing of the two side-by-side cockpits was retained on the initial production batch,
however these were later replaced by a single enclosed canopy,
and the gunners stations were upgraded with hydraulically driven Breda turrets.
Though it did possess outstanding range and endurance capabilities,
the Z501 was considered from the outset as a transitional aircraft. Its slow speed was a
concern, and the Italian Air Ministry had already issued development contracts with CANT and Macchi
for more modern and faster replacements. However, development of these aircraft became
painfully slow, and in the end neither of these new designs filled the gap they were intended for,
and so the Z.501 went from a transitional to a frontline role rather quickly.
The aircraft played a minor role during the Italian invasion of Ethiopia,
mostly conducting sea patrols and the occasional air-sea rescue mission,
but their most extensive use in the lead up to the second world war would be in Spain.
During the Spanish Civil war, at least 10 aircraft were operated by Nationalist forces. They were
flown on air-sea rescue missions, anti-submarine patrols, and general reconnaissance missions.
The general lack of effective air opposition meant that they enjoyed a relatively
peaceful time in the skies above and surrounding Spain. But the lack of said air opposition also
led to misleading convictions about the actual performance of the Z501
in a hostile theatre. There was also the question of the aircraft’s terrifying landing performance.
This was something that had not really been demonstrated, as the aircraft was often used
when the Mediterranean was about as flat as a mill pond. But a few incidents in Spain,
and then many more in the second world war, sharply highlighted the aircrafts
fluctuating behaviour when it came to landing on the water, something that led to many accidents,
often with fatal consequences. As it turned out, on rough landings,
the engine-induced inertia transmitted to the nacelle struts, combined with the rotary-inertia
of the propeller…caused said propeller disc to violently strike the upper frame of the hull.
The consequence was that, in addition to a damaged hull, the pilots often had their legs and/or arms
amputated…and this led to the aircraft being nicknamed ‘the slicer’.
Despite a proclivity for surgically removing the otherwise healthy limbs of its pilots,
and the nasty habit of the rear hull shattering on hard landings, the Z.501 would find itself
in service throughout the entirety of Italy’s involvement in the Second World War.
In fact they would find themselves serving on both sides after the Italian Armistice, with
both the allies and axis operating the aircraft. By the time of Italy’s involvement in 1940, they
were considered almost completely obsolete for frontline duties. However numerous delays in the
development of their replacement, and the benefit of their long range, kept them in service for far
longer than intended. The Z.501 operated in all theatres that featured Italian combat forces,
and across numerous engagements they succeeded in either damaging or sinking enemy submarines.
Unsurprisingly, their slow speed made them a sitting duck for enemy fighters, and an easy
target for land and sea based anti-aircraft batteries. This led to a high casualty rate
for the aircraft, especially during 1941 and 1942, when they saw the most action. By the end of 1942
there were still 199 aircraft in service, but of those only 88 were operational units. By 1943 this
number had dropped to 40 operational planes, and by war’s end just 10 were considered useable.
All of this being said, the Z.501 deserves credit for lasting as long as it did,
especially as it was only really effective in good weather that didn’t threaten the arms,
legs, or other body parts of its crews. Overall, however, it could not be considered a
great success. The aircraft built during the war suffered worse, often due to the poor quality of
wood used in their construction, which led to frequent visits to the hangar for hull repairs.
It was slow, structurally weak, handled poorly in high winds and rough seas, and of course there was
the whole trying to slice the crew in half issue. Along with being nicknamed the ‘slicer’, it was
sometimes called the ‘slug’ or even something along the lines of ‘help me mummy’ on account of
its extreme vulnerability to enemy fighters. Their profound weakness was did not escape the enemy,
and British Admiral A.B Cunningham noted in his memoirs that he could not help commiserating those
Italian aviators who, flying poorly manoeuvrable machines, had undertaken such a hopeless task.
Eventually, the Z.501s were replaced by better aircraft in frontline roles during the war,
notably the considerably more successful CANT Z.506, but their production run had been so large,
totalling 454 aircraft, that they were kept about for numerous secondary duties.
Remarkably, some remained in service all the way up to 1950, operating out of Sardinia.
Their successor, the Z.506, enjoyed a much better service life, setting numerous records,
and distinguishing itself as a patrol and air-sea rescue aircraft during the war.
It also didn’t try to kill its crew when landing in rough seas.
But that’s a story for another day. As always thank you so much for watching, and
thank you all for the kind words whilst I’ve been dealing with COVID and all the fun that entails,
and of course, a big thank you to the patreons. With a special shoutout to Kevin, Delliardo,
Bane, FB, Christopher R, Tronathon, Erik Hindman, John Austin Jr, Ray Culotta, Keith Tarrier,
Greenseaships, Northlincsweb, and MCT for their support as Wing Commander Tier Patreons.