View source for Stipa-Caproni

{{Short description|Italian experimental aircraft}}
{{Use Oxford spelling|date=May 2022}}
{{Use dmy dates|date=May 2022|cs1-dates=y}}
{|{{Infobox aircraft begin
| name = Stipa-Caproni
| image = Caproni Stipa on ground.jpg
| caption = The Stipa Caproni on the ground with the spats removed from its landing gear. Its light blue and cream paint scheme, similar to that on racing planes of the time, is visible, as is the opening at the trailing edge of its fuselage on which its [[rudder]] and [[Elevator (aircraft)|elevators]] were mounted. The rudder is painted in the colours of the [[Italian flag]].
}}
{{Infobox aircraft type
| type = Experimental aircraft
| manufacturer = [[Caproni]]
| designer = [[Luigi Stipa]]
| first flight = 7 October 1932
| introduced = 
| retired = 
| status = 
| primary user = {{Flag|Kingdom of Italy}}
| more users = 
| produced = 
| number built = 1
| variants with their own articles = 
}}
|}
[[File:Stipa-Caproni side view.jpg|thumb|The Stipa-Caproni with wheel spats removed.]]
The '''Stipa-Caproni''', also known as the '''Caproni Stipa''', was an experimental [[Italy|Italian]] aircraft designed in 1932 by [[Luigi Stipa]] (1900–1992) and built by [[Caproni]]. It featured a hollow, barrel-shaped [[fuselage]] with the [[Aircraft engine|engine]] and [[propeller (aircraft)|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 influenced the development of [[jet propulsion]].{{refn|{{Cite book |url=https://www.jstor.org/stable/j.ctt183q2zd |title=Jet Propulsion Engines |date=1959 |publisher=[[Princeton University Press]] |isbn=978-1-4008-7791-1 |editor-last=Lancaster |editor-first=Otis E. |series=High Speed Aerodynamics and Jet Propulsion |volume=12 |location=[[London]] |jstor=j.ctt183q2zd |oclc=491713256 |quote=The Stipa Aero plane built by Caproni in 1932 should be classified as a Jet Aircraft. The Stipa Aero plane can be considered as a predecessor of the Jet Aircraft of today. |url-access=subscription}}}}

==Stipa's design==
[[File:Caproni Stipa from front.jpg|thumb|left|A front view of the Stipa-Caproni, showing Stipa's [[intubed propeller]] design in which the propeller and [[Aircraft engine|engine]] are mounted inside a hollow tube which constitutes the aeroplane's [[fuselage]]. The spats have been removed from the landing gear.]] 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 propeller more efficient. This is a similar principle as is used in [[turbofan]] engines but used a piston engine to drive the compressor/propeller rather than a [[gas turbine]]. Stipa later became convinced that German [[rocket]] and jet technology (especially the [[V-1 flying bomb]]) was using his patented invention without giving proper credit, although his ducted fan design had little mechanically in common with turbojet engines and nothing at all with the pulsejet used on the V-1.

Stipa spent years studying the idea [[Mathematics|mathematically]] while working in the Engineering Division of the Italian [[Ministry of Defence (Italy)|Ministry of Air Force]], eventually determining that the venturi tube's inner surface needed to be shaped like an [[airfoil]] in order to achieve the greatest efficiency. He also determined the optimum shape of the propeller, the most efficient distance between the leading edge of the tube and the propeller, and the best rate of revolution of the propeller. Finally, he petitioned the Italian [[Italian fascism|Fascist]] government to produce a prototype aircraft. The government, seeking to showcase Italian technological achievement{{thinsp|—}}particularly in aviation{{thinsp|—}}contracted the [[Caproni]] company to construct the aircraft in 1932.{{refn|name=Guttman|{{Cite web |last=Guttman |first=Robert |date=2018-01-31 |orig-date=March 2010 |title=Caproni Flying Barrel |url=https://www.historynet.com/caproni-flying-barrel/ |url-status=live |archive-url=https://web.archive.org/web/20220306183856/https://www.historynet.com/caproni-flying-barrel/ |archive-date=2022-03-06 |access-date=2022-05-11 |website=Aviation History |location=[[Leesburg, Virginia]] |language=en-US |via=[[HistoryNet]] |issn=1076-8858 |oclc=1034294387}}}}

The resultant aircraft was a mid-wing monoplane of mostly wooden construction dubbed the Stipa-Caproni or Caproni Stipa. 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 [[Elevator (aircraft)|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 {{convert|120|hp|kW|adj=on}} [[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. It was painted in a blue-and-cream scheme of the type used on racing aircraft of the day, and its rudder bore the colours of the [[Italian flag]].{{r|Guttman}}

==Test flights==
[[File:Stipa-Caproni front quarter view.jpg|300px|thumb|right|A front quarter view of the Stipa-Caproni with wheel spats removed.]]
The Stipa-Caproni first flew on 7 October 1932 with [[Caproni]] company test pilot {{lang|it|Domenico Antonini|italic=no}} 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 {{convert|68|km/h|mph|abbr=on}} 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 {{convert|131|km/h|mph|abbr=on}}.{{r|Guttman}}

When Caproni had completed initial testing, the {{lang|it|Regia Aeronautica}} took control of the plane and transferred it to {{lang|it|[[Guidonia Montecelio]]|italic=no}} 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 consequent very short landing run.

As the plane did not perform noticeably better than conventional aircraft designs, the {{lang|it|Regia Aeronautica}} decided to cancel further development. No further prototypes were built.

==Influence==
Stipa himself never had intended his intubed propeller to be employed on single-engine aircraft like the Caproni-Stipa{{thinsp|—}}which he viewed merely as a [[testbed]]{{thinsp|—}}instead envisioning its use in large, multi-engine [[flying wing]] aircraft he had been designing in which the aerodynamic drag properties would not be significant, and the Italian government publicized the Stipa-Caproni's design as an example of Italian aviation technology prowess. None of Stipa's flying-wing aircraft designs were built, but experiences collected with the Stipa-Caproni did become an important influence in the development of the [[motorjet]]-powered [[Caproni Campini N.1]].{{r|Guttman}}

The test flights of the Stipa-Caproni also sparked much academic interest, and resulted in Stipa's work being studied in France, Germany, Italy, and the United Kingdom, and by the [[National Advisory Committee for Aeronautics]] in the United States. France designed{{thinsp|—}}but never constructed{{thinsp|—}}an advanced night [[bomber]] based on a Luigi Stipa design in the mid-1930s, and various aircraft designs such as the German [[Heinkel]] "T" [[Fighter (aircraft)|fighter]] of 1940 are thought to have incorporated some of Stipa's ideas as demonstrated by the Stipa-Caproni.{{r|Guttman}}

The [[Kort nozzle]] ducted fan of today{{thinsp|—}}designed in Germany in 1934{{thinsp|—}}uses many of Stipa's principles. The modern [[turbofan engine]] is thought by some aviation historians to be a descendant of the intubed propeller demonstrated in the Stipa-Caproni.{{r|Guttman}}

==Replica==
In [[Australia]], Lynette Zuccoli and Aerotec Queensland designed a 3/5-scale replica of the Stipa-Caproni, accurate even in terms of paint scheme and markings, powered by an Italian [[Simonini]] racing engine. They built it in 1998 and, in October 2001, succeeded in making two directional test flights with it with Bryce Wolff at the controls. Each flight covered about {{convert|600|m|yd|abbr=off}} and reached an altitude of approximately {{convert|6|m|ft|abbr=off}}, with Wolff reporting that the replica was very stable in flight and performed much as the Italian test pilots reported that the original aircraft had 69 years to the month earlier.{{refn|{{Cite web |last=Zuccoli |first=Lynette |date=December 2001 |title=Legends in Our Own Lunchtimes: The Stipa Caproni |url=http://www.seqair.com/Hangar/Zuccoli/Legends/Legends.html |url-status=live |archive-url=https://web.archive.org/web/20210602212824/http://www.seqair.com/Hangar/Zuccoli/Legends/Legends.html |archive-date=2021-06-02 |access-date=2022-05-11 |website=Gunder Restoration & Design |language=en-US}}}} The replica may never have flown again and is now on static display at [[Toowoomba City Aerodrome]] in Australia.{{r|Guttman}}

==Operators==
;{{flag|Kingdom of Italy}}
:''[[Regia Aeronautica]]''

==Specifications (original Stipa-Caproni)==
[[File:Caproni Stipa.svg|thumb]]
{{Aircraft specs
|ref=NACA Technical Memorandum No. 753 : Stipa Monoplane with Venturi Fuselage,{{refn|name=NACA|{{Cite magazine |last=Stipa |first=Luigi |author-link=Luigi Stipa |date=1933-07-07 |title=Stipa Monoplane with Venturi Fuselage |url=https://ntrs.nasa.gov/api/citations/19930094664/downloads/19930094664.pdf |url-status=live |magazine=NACA Technical Memorandum |language=en-US |location=[[Washington D.C.]] |publisher=[[National Advisory Committee for Aeronautics]] |issue=753 |archive-url=https://archive.today/20220511040924/https://ntrs.nasa.gov/api/citations/19930094664/downloads/19930094664.pdf |archive-date=2022-05-11 |access-date=2022-05-11}}}} Aeroplani Caproni: Gianni Caproni and His Aircraft, 1910–1983{{refn|name=Abate|{{Cite book |last1=Abate |first1=Rosario |title=Aeroplani Caproni: Gianni Caproni and His Aircraft, 1910-1983 |last2=Alegi |first2=Gregory |last3=Apostolo |first3=Giorgio |date=1992 |publisher=Museo Caproni |location=[[Trento]] |language=en |asin=B000TC8DE4 |oclc=237798156}}}}
|prime units?=met
<!--
        General characteristics
-->
|crew=1 or 2
|length m=6.04
|length note=
|span m=14.30
|span note=
|height m=3.24
|height note=
|wing area sqm=19
|wing area note=
|aspect ratio=<!-- sailplanes -->
|airfoil=
|empty weight kg=570
|empty weight note=
|gross weight kg=850
|gross weight note=
|max takeoff weight kg=
|max takeoff weight note=
|fuel capacity=
|more general=
<!--
        Powerplant
-->
|eng1 number=1
|eng1 name=[[de Havilland Gipsy III]]
|eng1 type=4-cylinder inverted air-cooled in-line piston engine
|eng1 kw=90
|eng1 note=

|prop blade number=2
|prop name=ground-adjustable propeller
|prop dia m=<!-- propeller aircraft -->
|prop dia note=
<!--
        Performance
-->
|max speed kmh=133
|max speed note={{br}}
*'''Landing speed''': {{convert|68|km/h|mph|abbr=on}}
|cruise speed kmh=
|cruise speed note=
|stall speed kmh=
|stall speed note=
|never exceed speed kmh=
|never exceed speed note=
|minimum control speed kmh=
|minimum control speed note=
|range km=
|range note=
|ferry range km=
|ferry range note=
|endurance=<!-- if range unknown -->
|ceiling m=3700
|ceiling note=
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|climb rate ms=
|climb rate note=
|time to altitude={{cvt|3000|m}} in 40 minutes
|wing loading kg/m2=44.73
|wing loading note= at {{cvt|850|kg|0}}
|fuel consumption kg/km=
|power/mass={{cvt|0.064|hp/lb|order=flip}}
|more performance={{br}}
*'''Take-off run:''' {{cvt|180|m}}
*'''Landing run:''' {{cvt|180|m}}
}}

==References==
{{reflist}}

==Further reading==
* {{Cite book |last=Thompson |first=Jonathon W. |url=https://archive.org/details/italiancivilmili00libg |title=Italian Civil and Military Aircraft 1930-1945 |publisher=Aero Publishers Inc. |year=1963 |isbn=0-8168-6500-0 |location=USA |page=[https://archive.org/details/italiancivilmili00libg/page/n49 97] |url-access=limited}}
* {{cite patent |country=US |number=2071221 |title=Airplane |gdate=1937-02-16}}
* {{Cite web |title=Luigi Stipa - a pioneer of jet flying |url=https://www.aerotec.com.au/luigi-stipa.html |url-status=live |archive-url=https://web.archive.org/web/20220313135249/https://www.aerotec.com.au/luigi-stipa.html |archive-date=2022-03-13 |access-date=2022-05-11 |website=Aerotec Queensland |language=en-AU}}
* {{Cite web |date=January 1933 |title=New Italian Airplane for High Speed is a Flying Tunnel |url=http://blog.modernmechanix.com/2006/08/18/new-italian-airplane-for-high-speed-is-a-flying-tunnel/ |url-status=dead |archive-url=https://web.archive.org/web/20120210145958/http://blog.modernmechanix.com/2006/08/18/new-italian-airplane-for-high-speed-is-a-flying-tunnel/ |archive-date=2012-02-10 |access-date=2022-05-11 |website=Modern Mechanix |language=en-US}}
* {{Cite AV media |url=https://www.youtube.com/watch?v=xYqr2h_xQRk |title=Stipa-Caproni Flying Barrel (take-off footage only) |date=2007-09-30 |publisher=Bomberguy |via=[[YouTube]]}}
* {{Cite AV media |url=https://www.youtube.com/watch?v=mQ0ZQesixms |title=1933 Voli sperimentali aeroplano Stipa Caproni |date=2012-10-12 |language=it |publisher=Milan Airports |trans-title=1933 Stipa Caproni airplane experimental flights |via=[[YouTube]]}}

==External links==
{{commons category|Stipa-Caproni}}
*[https://books.google.com/books?id=fP1ZBQFdpMAC&dq=Flight+Journal+stipa+caproni&pg=PA231 Anonymous, "The Caproni Flying Barrel", ''Flying Magazine'', April 1933, p. 231.]
*[https://www.youtube.com/watch?v=mQ0ZQesixms Video "1933 Voli sperimentali aeroplano Stipa Caproni" on YouTube] 
*[https://www.youtube.com/watch?v=ErX-sIjew4A Video "A Bizarre Fat Airplane that Changed Military Aviation Forever" on YouTube]

{{Caproni aircraft}}
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[[Category:Caproni aircraft]]
[[Category:1930s Italian experimental aircraft]]
[[Category:Aircraft first flown in 1932]]
[[Category:Ducted fan-powered aircraft]]
[[Category:Mid-wing aircraft]]
[[Category:Single-engined tractor aircraft]]