Caproni Stipa (Flying Barrel)

https://en.wikipedia.org/wiki/Stipa-Caproni

The Stipa-Caproni, also generally called the Caproni Stipa, was an experimental
Italian aircraft designed in 1932 by Luigi Stipa (1900–1992) and built by
Caproni. It featured a hollow, barrel-shaped fuselage with the engine and
propeller completely enclosed by the fuselage—in essence, the whole fuselage was
a single ducted fan. Although the Regia Aeronautica (Italian Royal Air Force)
was not interested in pursuing development of the Stipa-Caproni, its design was
an important step in the development of jet propulsion.

The design of the Stipa-Caproni was very similar to that of modern jet engines;
in fact, after having patented his design in Italy, Germany, and the United
States in 1938, Stipa became convinced that German rocket and jet technology
(especially the V-1 flying bomb) was using his patented invention without giving
proper credit. Stipa's basic idea—which he called the "intubed propeller"—was to
mount the engine and propeller inside a fuselage that itself formed a tapered
duct, or venturi tube, and compressed the propeller's airflow and the engine
exhaust before it exited the duct at the trailing edge of the aircraft,
essentially applying Bernoulli's principle of fluid movements to make the
aircraft's engine more efficient.

The resulting aircraft—a midwing monoplane of mostly wooden construction dubbed
the Stipa-Caproni or Caproni Stipa—was strikingly ungainly in appearance. The
fuselage was a barrel-like tube, short and fat, open at both ends to form the
tapered duct, with twin open cockpits in tandem mounted in a hump on top of it.
The wings were elliptical and passed through the duct and the engine nacelle
inside it. The duct itself had a profile similar to that of the airfoils, and a
fairly small rudder and elevators were mounted on the trailing edge of the duct,
allowing the ducted propeller wash to flow directly over them as it exited the
fuselage to improve handling. The propeller was mounted inside the fuselage
tube, flush with the leading edge of the fuselage, and the 120-horsepower de
Havilland Gipsy III engine that powered it was mounted within the duct behind it
at the midpoint of the fuselage. The aircraft had low, fixed, spatted main
landing gear and a tailwheel, making it look as if it was squatting when on the
ground. It was painted in a blue-and-cream scheme of the type used on racing
aircraft of the day, and its rudder bore the colors of the Italian flag.


Role
Experimental aircraft

Manufacturer
Caproni

Designer
Luigi Stipa

First flight
7 October 1932

Primary user
Italy

Number built
1

The Stipa-Caproni first flew on 7 October 1932 with Caproni company test pilot
Domenico Antonini at the controls. Initial testing showed that the "intubed
propeller" design did increase the engine's efficiency as Stipa had calculated,
and the additional lift provided by the airfoil shape of the interior of the
duct itself allowed a very low landing speed of only 68 km/h (42 mph) and
assisted the Stipa-Caproni in achieving a higher rate of climb than other
aircraft with similar power and wing loading. The placement of the rudder and
elevators in the exhaust from the propeller wash at the trailing edge of the
tube gave the aircraft handling characteristics that made it very stable in
flight, although they later were enlarged to further improve the plane's
handling characteristics. The Stipa-Caproni proved to be noticeably quieter than
conventional aircraft of the time. Unfortunately, the "intubed propeller" design
also induced so much aerodynamic drag that the benefits in engine efficiency
were cancelled out, and the aircraft's top speed proved to be only 131 km/h (81
mph).

When Caproni had completed initial testing, the Regia Aeronautica took control
of the plane and transferred it to Guidonia Montecelio for a brief series of
further test flights. All test pilots reported that the plane was extremely
stable in flight, to the point where it was difficult to change course; test
pilots were also astounded by the very low landing speed and the consequently
very short landing run.

Specifications (original Stipa-Caproni)

Crew: 1 or 2
Length: 5.88 m (19 ft 4 in)
Wingspan: 14.28 m (46 ft 10 in)
Height: 3 m (9 ft 10 in)
Loaded weight: 800 kg (1,760 lb)
Powerplant: 1 × de Havilland Gipsy III inline piston engine, 120 hp (90kW)
Propellers: 1 propeller, 1 per engine

Performance
Maximum speed: 131 km/h (81 mph)

Landing speed: 68 km/h (42 mph)




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