When discussing Italian fighters of the Second World War, three builders are prominent; Fiat, with their CR.32 and -42 biplanes, followed by their G.50 and -55 fighters; Macchi, with the C.200 series; And Reggiane with their Re.2000 series.
While these manufacturers products acquired somewhat dubious reputations during the early days of Italy’s involvement in the War, they would all produce greatly improved aircraft in a short period, culminating in the superb fighters of the so-called Serie 5.
But there is one other company that did actually get fighters into service with the Royal Italian Air Force, one that now is barely remembered.
This was a subsidiary of the Caproni conglomerate, as was Reggiane, and like just about every other aircraft builder in the country they answered the calls for new fighters that the Regia Aeronautica put out in the latter half of the 1930s. Indeed, it is a little surprising that Caproni Vizzola didn’t get a full production contract, because they hit the ground running, not developing one potential fighter, but two!
The F.4 and F.5 were created in tandem, both using the same construction technique of welded steel tube fuselage with a flush riveted duralumin skin, while the wings were of all wooden construction. This mixed-construction technique was not an unusual approach for the day, with design work on both beginning in late 1937.
But what Caproni did was anticipate how future Italian designs would go, because the difference between the two proposed aircraft was in the engine type, with the F.4 being designed to use a liquid-cooled inline, while the F.5 was built for an air-cooled radial.
This is a bit of a roundabout story so bear with me, and let’s start with the F.5, because this is the only one of the aircraft to actually get into service and I think starting with it will make it easier to describe the F-series’ development and history.
The F.5 was, as said, designed at the same time as the F.4, but while the latter aircraft was designed to use a liquid-cooled engine, specifically the Isotta-Fraschini Asso 121 R.C.40, the F.5 was built to use an air-cooled radial. This was the Fiat A.74, a fourteen-cylinder engine that was fitted to basically all of the Royal Italian Air Forces primary fighters of the time; the CR.42, Macchi 200 and Fiat G.50.
As such the F.5 was very much in line with the Italian’s contemporary thinking in its fighter requirements and, as it demonstrated excellent maneuverability when the prototype first flew in February 1939, elicited a lot of interest. This in turn led to an order for a second prototype and twelve pre-production aircraft, with the F.5 looking like becoming a standard type operating with the Italians.
The F.5 was a fairly typical Italian fighter of its day, having good agility but weak firepower with only two 12.7mm heavy machine guns and a decidedly average performance, with a top speed of 320mph (515km/h). The service aircraft produced would all initially be put into a fighter squadron, but by 1942 were all serving in a night fighter squadron.
From there they largely disappear from history as a type made in very limited numbers, because only eleven of the aircraft would actually get into service and their fate seems to have disappeared into the chaos that is Italy’s history during World War Two.
So why did only eleven of the preproduction aircraft see service?
Well, now we can jump back to the F.4.
As I explained before, this aircraft had been intended to be the variant that used a liquid-cooled engine. But the Italian authorities weren’t very keen on using such powerplants in their fighters during the immediate pre-war period, instead preferring to use them on aircraft like bombers and reconnaissance types. So, the F.4 was swiftly rejected before a prototype was even built.
But that all changed in 1939. That summer, Italy received its first examples of the German’s Daimler Benz DB601A engine. This produced 1,175hp and was the powerplant step up that Italian airframes had been crying out for.
Suddenly the F.4 was back on the table, and the final preproduction F.5 was taken off the production line, fitted with one of the DB 601s and redesignated as the earlier model number.
This first flew in July 1940 and, like the contemporary Macchi C.202 and Reggiane R.2001 which were both similar types essentially converted to use the new engine, showed marked improvement. The F.4 recorded a top speed of 340mph (547km/h), again basically the same as its contemporaries in Italian service, though now more in line with other nations aircraft, though the armament remained the same, weak twin heavy machine guns.
But the aircraft certainly had a clean appearance and like the F.5, the F.4 was comparable enough to Italy’s service fighters that consideration was once again given to building the type for service, especially as Italy had now negotiated a licence to produce the DB601A for themselves. But this time it seems to have been Caproni that decided not to proceed with the aircraft.
I’m speculating here, and happy to be corrected if anyone knows better, but I wonder if this was due to the experiences of the Caproni groups Reggiane subsidiary and the issues they had getting enough engines for the R.2001.
Macchi seem to have largely monopolized the supply of the licence built DB601s, a factor that saw their MC.202 built in much larger numbers than their Reggiane rival. To be fair, that was probably the right choice as the MC.202 was a great aircraft that gave the Italians something immediately that put them on an equal footing with Allied fighters.
Plus, it is also notable that Fiat also didn’t really bother building a variant of their Fiat G.50 with the DB 601, limiting efforts to a single test type. Instead, they jumped straight to the G.55, fitted with the much more powerful DB 605 engine.
And Caproni Vizolla seem to have mimicked them, deciding to develop the F.6M which used this engine too.
In recognition, as with other Italian fighters, that armament and airframes needed strengthening, the F.6 took the F.5 basic design and changed the wings to all metal (hence the “M” in the designation), adding placements for an additional two heavy machine guns, though these apparently weren’t fitted to the prototype.
The DB 605 produced 1,475hp as standard but the F.6 prototype had a rather clumsy and large fixed radiator mounted under the nose that impeded the aircraft’s performance when it flew for the first time in September 1941.
I suspect this explains the rather poor listed performance of the type. In theory the aircraft was a match for its contemporaries in the Serie 5. But while those generally had top speeds listed at around 390mph (628km/h), the F.6M is recorded as having a maximum speed of only 354mph (570km/h).
Of course, the other aircraft, as production types, had had a considerable amount of effort expended in their ongoing development but still, the disparity is stark.
The F.6M went back to the factory for reworking, and this saw the radiator moved to a belly position.
Now, I don’t know if the listed top speed figure for the F.6 is for the earlier or later version, though as I said I suspect the former. Because unfortunately the F.6M was soon lost in a landing accident that ending the program. Instead, Caproni threw themselves into yet another variant, the F.6Z.
This would have the Isotta-Fraschini Zeta R.C.25/60 24-cylinder X-type engine and a prototype was ordered by the Italian Air Ministry in June 1942.
To fit the new engine, armament on the F.6Z was once again altered with one of the nose-mounted guns removed, reducing loadout to three heavy machine guns.
But the Zeta, as it was called, would follow the classic example of pretty much all of the X-type engines, proving a bit of a developmental nightmare. So it wasn’t until August 1943 that the F.6Z first flew, and the engine performed pretty abysmally, generating far less than the hoped for 1,500hp.
Obviously considerable work still needed to be done, and one suspects that the F.6 was being used more as an engine development program by this point as the licence produced DB 605 were all fully committed to the new Italian fighters and no doubt a new, powerful indigenous engine would be most welcome.
But that was all for naught, because weeks after the F.6Z first flew, the Italians capitulated, signing an armistice with the Allies and splitting into warring factions fighting on both sides of the conflict.
This ended any development of new fighters and engines, including an alleged attempt to develop an F.7. Details are confused about this, with it either being an F.6 with an even more powerful DB 603 engine or else an F.6 with an improved fuselage.
Either way, it’s irrelevant because it never was more than at best a paper design study and, like the other advanced fighter proposed by the Italians, came to nothing once the country collapsed.
And that is the story of the Caproni Vizolla F-series fighters, interesting “what-ifs” that would have added even more complexity to the Royal Italian Air Force had they got into service in anything more than the tiny number built.