RogerBW's Blog

Caproni Ca.60 14 February 2014

The Caproni Ca.60, called the Noviplano or Capronissimo, was a prototype flying-boat airliner. Built in 1921, it was pretty early in the development of flying boats: the first commercial service using them didn't start until 1923, and they were generally small aircraft. The Curtiss NC-4, introduced in 1919, had a crew of six and no room for passengers; the Felixstowe F.5 was a patrol bomber with a crew of four.

Giovanni Battista Caproni reckoned he could do better: the Ca.60 would have a crew of eight, and carry a hundred passengers! This was unheard-of; at the same time, de Havilland was looking at increasing capacities with the ten-passenger DH.29 Doncaster and the eight-passenger DH.32. Seaplanes could be larger, of course, but even the Boeing 314 Clipper, not introduced until 1938, only took 74. A hundred? Clearly the aircraft would be huge, and need so much structural bracing that it would never fly.

Caproni had a Plan. He also had plenty of experience: he'd built the first aircraft constructed in Italy (which was destroyed on its first flight, but that wasn't wildly unusual in those days). He'd built bombers during the Great War. His scheme was simple: rather than having all the weight of the aircraft borne through a single set of wing struts, he'd have three separate wing assemblies, mounted at fore, middle and aft of the fuselage and braced together. They'd need to be pretty wide wings (a hundred-foot span, though the aircraft was only 77 feet long), so a pontoon on each side would lend stability. What's more, each wing assembly would consist of three separate wings, stacked vertically: a triple triplane, hence Noviplano. The wings were probably borrowed from war-surplus Caproni Ca.4 bombers.

The plane would carry eight engines (Liberty L-12s, a workhorse American design that had come in mostly too late for the Great War) for a total of 3200 horsepower; quite respectable. Range is questionable; some sources estimate about 400 miles, but this thing was in theory meant to be able to cross the Atlantic, and that would have meant an awful lot of refuelling stops.

Unfortunately, during its first flight, the Capronissimo only got about sixty feet above the surface of Lake Maggiore, then went into a dive and crashed, breaking up on impact. The pilot, Sr. Semprini, escaped unhurt. There's a persistent rumour that he crashed it so that nobody else would have the terrifying experience of flying it; at any rate, the wreckage was towed to shore and stored, as Caproni planned to rebuild it. That night, the storage building mysteriously caught fire, and all remnants of the Ca.60 were destroyed.

Why wouldn't it have been a good flyer? The centre of lift (in line with the middle wing, more or less) would have been well above the centre of mass (probably in the top of the fuselage, even with the wing-mounted engines); that would leave the aircraft very stable, prone to choose a flight attitude and keep to it. What's more, the offset of the cockpit would leave the pilot subject to rotational forces when climbing, diving or turning, tending to push him forwards and down out of his seat; all large aircraft do this to some extent, but most manage to keep the cockpit in line with, or above, the centre of rotation.

The crash may have been caused by shifting ballast: the plane couldn't be flown empty, and its stability would make it very difficult to recover once it had gone into a dive. The aircraft's power-to-weight ratio wasn't bad by the standards of its day, but all the rigging needed for the three triple wings (and the pontoons too) would have produced an immense amount of drag, much of it actually in the airflow from the engines.

What's worse, the choppy and downward-flowing air from the first set of wings would hit the second, providing less lift than was wanted; this in turn would push the third set down even more. In retrospect the multiplane wing is an historical dead end: it's easier to build than a monoplane, because you can use cross-bracing and effectively turn the aircraft into a box-girder, but all those struts and wiring produce far more drag than a monoplane wing of the same lift. But the in-series wing is even more of a dead end, having never been successful at all.

  1. Posted by Owen Smith at 01:47pm on 14 February 2014

    Every mad inventor should have one.

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