Blackburn B-20
{{Use dmy dates|date=October 2019}}
{{Use British English|date=February 2017}}
{{Infobox aircraft
|name=Blackburn B-20
|image=Blackburn B-20.svg
|caption=
|type=Prototype flying boat
|manufacturer=Blackburn Aircraft
|national_origin=United Kingdom
|designer=John Douglas Rennie
|first_flight=26 March 1940
|introduction=
|retired=
|status=
|primary_user= Royal Air Force
|more_users=
|produced=
|number_built=1
|unit cost=
|variants=
}}
The Blackburn B-20 was an experimental aircraft, first flying in 1940, that attempted to drastically increase the performance of flying boat designs. Blackburn Aircraft undertook an independent design study based on a patent filed by their chief designer, John Douglas Rennie{{Ref Jane's|Blackburn B.20|107}} for a retractable pontoon float that formed the planing hull.
Design and development
The B-20 was an attempt to combine the best features of both the flying boat and the floatplane. While on the water, the B-20 was essentially a floatplane, using a large float under the fuselage for buoyancy, and two smaller floats near the wingtips for stability. In flight, the main float retracted upwards towards the fuselage, fitting into a "notch" to become streamlined as a part of the fuselage. The wing floats folded outwards, somewhat like those on the American Consolidated PBY flying boat design, to become the wingtips.{{cite web|last=Dell|first=John|work=Dinger's Aviation Pages|accessdate=19 August 2006|url=http://freespace.virgin.net/john.dell/blackburn_b20.htm|title=Blackburn B20|url-status=dead|archiveurl=https://web.archive.org/web/20090609132412/http://freespace.virgin.net/john.dell/blackburn_b20.htm|archivedate=9 June 2009}} This configuration gave the correct wing incidence for takeoff and for flight and in the latter a much reduced drag compared to the deep hulls of flying boats.Buttler
Blackburn, along with Supermarine, Shorts and Saunders-Roe tendered designs against Air Ministry Specification R1/36. The Supermarine was chosen initially but Supermarine could not start work soon enough (due to their work on the Spitfire) and what would enter service as the Saunders Roe Lerwick became the chosen aircraft. However, the Ministry was interested enough to authorise and contract for the construction of a prototype of the B-20, serial number V8914, to test the concept.
Testing
The prototype, built at Dumbarton, flew for the first time on 26 March 1940. On 7 April, during a test run, the aircraft experienced extreme vibration due to aileron flutter and the crew bailed out. Three were lost, the other two were picked up by {{HMS|Transylvania}}, a converted merchantman. Development ceased when the first prototype crashed, as Blackburn's resources were dedicated to the war effort. The Ministry felt the concept had been proven and the crash was not due to the pontoon design.
The aircraft's wreck still exists, but remains undisturbed as it is designated a War grave. In 1998, one of the engines was raised as it had been caught in a fishing boat's nets and dragged away from the wreck, into shallower water. It is currently an exhibit in the Dumfries and Galloway Aviation Museum.{{cite web
| last = Dell
| first = John
| title = Blackburn B-20
| url = http://freespace.virgin.net/john.dell/blackburn_b20.htm
| accessdate = 9 September 2009
| url-status = dead
| archiveurl = https://web.archive.org/web/20090609132412/http://freespace.virgin.net/john.dell/blackburn_b20.htm
| archivedate = 9 June 2009
| df = dmy-all
}}
B.40
The B-40 was an improved variant of the B-20 with Bristol Centaurus engines to meet a requirement for a small general purpose flying boat and specification R.13/40 was raised for it.Meekcoms/Morgan 1994, p. 287 Two prototypes were ordered in September 1941 but the situation was reconsidered in December. Its range was insufficient improvement over the Sunderland III, performance on one engine was unacceptable, and land-based patrol aircraft were capable of covering longer ranges. Further, there was little value as an experimental design because the principle had been proven in the B.20 and for an aircraft the size of the B.40 there would not be a significant improvement in drag. With no operational requirement for the B.40, it was therefore cancelled.Buttler. British Secret Projects Fighters and Bombers 1935–1950 Midland Publishing
Specifications (B-20, as designed)
{{Aircraft specs
|ref=Jane's Fighting Aircraft of World War II
|prime units?=imp
|crew=6
|length ft=69
|length in=8
|length note=
|span ft=82
|span in=0
|span note=floats retracted
|height ft=25
|height in=2
|height note=hull extended
|wing area sqft=1066
|wing area note=
|aspect ratio=
|airfoil=
|empty weight lb=
|empty weight note=
|gross weight lb=
|gross weight note=
|max takeoff weight lb=35000
|max takeoff weight note=
|fuel capacity=
|more general=
|eng1 number=2
|eng1 name=Rolls-Royce Vulture
|eng1 type=X-24 liquid-cooled piston engines
|eng1 hp=1720
|eng1 note=
|prop blade number=3
|prop name=Rotol constant-speed feathering propellers
|prop dia ft=
|prop dia in=
|prop dia note=
|max speed mph=306
|max speed note=at {{cvt|15000|ft|0}}
|cruise speed mph=
|cruise speed note=
|stall speed mph=
|stall speed note=
|never exceed speed mph=
|never exceed speed note=
|minimum control speed mph=
|minimum control speed note=
|range miles=1500
|range note=
|combat range miles=
|combat range note=
|ferry range miles=
|ferry range note=
|endurance=
|ceiling ft=
|ceiling note=
|climb rate ftmin=
|climb rate note=
|time to altitude=
|lift to drag=
|wing loading lb/sqft=
|wing loading note=
|fuel consumption lb/mi=
|power/mass=
|more performance=
|guns=provision for two turrets and other defensive positions
|bombs=bomb-cells in centre section
}}
See also
{{Aircontent
|related=
|similar aircraft=
|lists=
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}}
Notes
{{reflist|30em}}
Bibliography
- {{cite web|title=Blackburn B-20|url=http://www.britishaircraft.co.uk/aircraftpage.php?ID=304|work=British Aircraft Directory|date=20 July 2003|url-status=bot: unknown|archiveurl=https://web.archive.org/web/20070930153915/http://www.britishaircraft.co.uk/aircraftpage.php?ID=304|archivedate=30 September 2007}}
- {{cite journal|last=Bussy|first=Geoffrey|year=2006|title=Blackburn's Amazing B-20 Flying Boat|journal=Air Enthusiast|publisher=Key Publishing|location=Stamford, UK|issue=124|pages=28–29|issn=0143-5450}}
- {{cite book|last=Buttler|first=Tony|title=British Secret Projects: Fighters & Bombers 1935–1950|year=2004|publisher=Midland Publishing|location=Hinckley, UK|isbn=1-85780-179-2}}
- {{cite book|last=Jackson|first=A. J.|title=Blackburn Aircraft Since 1909|year=1989|publisher=Putnam|location=London|isbn=0-85177-830-5}}
- {{cite book |last=Meekcoms |first=K. J.|author2=Morgan, E. B.| title= The British Aircraft Specification File | date=1994 |publisher=Air-Britain | location=Tonbridge, UK | isbn=0-85130-220-3}}
- {{cite book|last=Townend|first=David R|title=Clipped Wings – World War Two Edition|year=2010|publisher=Aerofile Publications|location=Markham, UK|isbn=978-0-9732020-1-4}}
External links
{{commons category|Blackburn B-20}}
- [http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%200749.html "A Teaser in Hydraulics"] Flight 1946 p383-384. – details of the float mechanism
- [http://1000aircraftphotos.com/Contributions/HornDavid/11895.htm A photo of the B-20 V8914 on its beaching gear] and afloat [http://1000aircraftphotos.com/Contributions/Visschedijk/Additions/11895L-1.jpg]
- [http://www.dingeraviation.net/B20/blackburn_b20.htm Dinger's Aviation Pages: Photos and data on Blackburn B20] {{Webarchive|url=https://web.archive.org/web/20180417022847/http://www.dingeraviation.net/B20/blackburn_b20.htm |date=17 April 2018 }}
{{Blackburn aircraft}}
Category:1940s British experimental aircraft