Lockheed XC-35
{{Use American English|date=November 2024}}
{{Use dmy dates|date=October 2024}}
| {{Infobox aircraft begin
| name= XC-35 | image=Lockheed_XC-35.jpg | caption= Lockheed XC-35 }}{{Infobox aircraft type | type=Experimental | national origin= United States | manufacturer= Lockheed | designer= | first flight= 9 May 1937 | introduced= 1937 | retired= | status= In storage at the Smithsonian Institution's National Air and Space Museum | primary user= United States Army Air Corps | number built= 1 | developed from= Lockheed Model 10 Electra | variants with their own articles= }} |
The Lockheed XC-35 is a twin-engine, experimental pressurized airplane. It was the second American aircraft to feature cabin pressurization.The distinction of the world's first pressurized aircraft goes to a heavily modified Engineering Division USD-9A which flew in the United States in 1921.{{cite book|last=Cornelisse |first= Diana G. |title=Splendid Vision, Unswerving Purpose; Developing Air Power for the United States Air Force During the First Century of Powered Flight |location= Wright-Patterson Air Force Base, Ohio |publisher= U.S. Air Force Publications |year=2002 |isbn=0160675995 |pages=128–129}} It was initially described as a "supercharged cabins" by the Army. The XC-35 was a development of the Lockheed Model 10 Electra that was designed to meet a 1935 request by the United States Army Air Corps for an aircraft with a pressurized cabin.[http://collections.nasm.si.edu/code/emuseum.asp?profile=objects&newstyle=single&quicksearch=A19600294000 Lockheed XC-35 Electra], Smithsonian Institution National Air and Space Museum.
Design and development
The United States Air Corps wanted the aircraft to perform high altitude research and to test the feasibility of a pressurized cabin. The Corps contracted with Lockheed Aircraft Corporation to produce the aircraft at a total cost of $112,197. The requirements called for an aircraft capable of flying at no less than 25,000 ft (7,620 m) and having an endurance of ten hours with at least two hours above 25,000 ft (7,620 m). Major Carl Greene and John Younger, both structures experts who worked for the Air Corps Engineering Division at Wright Field in Ohio were responsible for the design of the pressurized cabin structure. Greene and Younger worked with Lockheed to modify a Model 10 Electra with a new fuselage consisting of a circular cross-section that was able to withstand up to a 10 psi differential.[http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=3296 Lockheed XC-35] {{webarchive|url=https://web.archive.org/web/20141218223002/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=3296 |date=2014-12-18 }}, National Museum of the Air Force. New, smaller windows were used to prevent a possible blowout while operating at high pressure differentials. The cabin pressurization was provided by bleeding air from the engines' turbo supercharger, the compressor outlet fed into the cabin and was controlled by the flight engineer.[http://www.airspacemag.com/history-of-flight/Airplanes_that_Transformed_Aviation.html?c=y&page=2 Airplanes that Transformed Aviation], Air & Space Magazine. This system was able to maintain a cabin altitude of 12,000 ft (3,658 m) while flying at 30,000 ft (9,144 m).{{usurped|1=[https://web.archive.org/web/20111003183507/http://www.airforce-magazine.com/MagazineArchive/Pages/2003/January%202003/0103bomber.aspx Van Patten, Robert E.]}} Air Force Magazine Online, Vol.86, No.1 January 2003 The fuselage was divided into two compartments, a forward pressurized compartment, and an aft unpressurized compartment. The forward compartment housed two pilots, a flight engineer, and up to two passengers. The aft compartment provided accommodation for one passenger and could be used only at low altitudes since it lacked pressurization.
The XC-35 was fitted with two Pratt & Whitney XR-1340-43 engines of 550 hp (410 kW) each compared to the two Pratt & Whitney R-985-13 of 450 hp (336 kW) fitted to the base Model 10 Electra. The engines featured a turbo supercharger to permit the engines to operate in thin air at high altitudes.
Operational history
The XC-35 was delivered to Wright Field, Ohio in May 1937, made its first performance flight on 5 August, and was involved in an extensive flight testing program for which the Army Air Corps was awarded the Collier Trophy. The lessons learned from the XC-35 played a key role in the development of the Boeing 307 Stratoliner and the B-29 Superfortress which was to be the first mass-produced pressurized aircraft.
The Air Corps brass were so confident in the new technology that they allowed the XC-35 to be used as an executive transport for Louis Johnson, the Assistant Secretary of War and future Secretary of Defense.
In 1943, NACA pilot Herbert H. Hoover flew the XC-35 into thunderstorms to gather data on the effects of severe weather on aircraft in flight.[http://www.nasaimages.org/luna/servlet/detail/nasaNAS~2~2~8020~109676: Herbert H. Hoover & Lockheed XC-35], NASA Image eXchange Collection {{webarchive |url=https://web.archive.org/web/20090521091817/http://www.nasaimages.org/luna/servlet/detail/nasaNAS~2~2~8020~109676 |date=21 May 2009 }}
The XC-35 was donated to the Smithsonian Institution's National Air and Space Museum in 1948 and remains there in long term storage.
Specifications (Lockheed XC-35)
File:Lockheed XC-35 aft pressure bulkhead.jpg
{{Aircraft specs
|ref=Lockheed aircraft since 1913{{cite book |last1=Francillon |first1=René J. |title=Lockheed aircraft since 1913 |date=1988 |publisher=Naval Institute Press |location=Annapolis |isbn=0870218972 |pages=118–129 |edition=2nd reprint}}
|prime units?=imp
|crew=up to 6
|capacity=
|length ft=38
|length in=7
|length note=
|span ft=55
|span in=
|span note=
|height ft=10
|height in=1
|height note=
|wing area sqft=458.5
|wing area note=
|aspect ratio=
|airfoil=root: Clark Y (18%); tip: Clark Y (9%){{cite web |last1=Lednicer |first1=David |title=The Incomplete Guide to Airfoil Usage |url=https://m-selig.ae.illinois.edu/ads/aircraft.html |website=m-selig.ae.illinois.edu |access-date=16 April 2019}}
|empty weight lb=7940
|empty weight note=
|gross weight lb=10500
|gross weight note=
|max takeoff weight lb=
|max takeoff weight note=
|fuel capacity=
|more general=
|eng1 number=2
|eng1 name=Pratt & Whitney R-1340-43
|eng1 type=9-cylinder turbo-supercharged air-cooled radial piston engine2
|eng1 hp=550
|eng1 note=
|prop blade number=2
|prop name=variable-pitch propellers
|prop dia ft=
|prop dia in=
|prop dia note=
|max speed mph=236
|max speed note=at {{cvt|20000|ft|0}}
|cruise speed mph=214
|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=
|range note=
|endurance=
|ceiling ft=31500
|ceiling note=
|climb rate ftmin=1125
|climb rate note=
|time to altitude=
|lift to drag=
|wing loading lb/sqft=22.9
|wing loading note=
|fuel consumption lb/mi=
|power/mass={{cvt|0.105|hp/lb}}
|more performance=
|avionics=
}}
See also
References
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External links
{{commons category|Lockheed XC-35}}
- [http://airandspace.si.edu/collections/artifact.cfm?id=A19600294000 XC-35 in the collection of the National Air and Space Museum] {{Webarchive|url=https://web.archive.org/web/20160304024410/http://airandspace.si.edu/collections/artifact.cfm?id=A19600294000 |date=2016-03-04 }}
- [https://web.archive.org/web/20141218223002/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=3296 XC-35 from National Museum of the United States Air Force]
- [http://www.aviation-history.com/garber/vg-bldg/lockheed_XC35-1_f.html Lockheed XC-35 (10E) Electra]
- [http://1000aircraftphotos.com/APS/3717.htm Lockheed 10-E XC-35 (36-353 c/n 3501)]
- [https://web.archive.org/web/20070828081009/http://www.nationalmuseum.af.mil/factsheets/factsheet_media.asp?fsID=3296 XC-35 Photo Gallery] from National Museum of the United States Air Force
{{Lockheed Model 10 Electra family}}
{{Lockheed}}
{{USAF transports}}
Category:1930s United States experimental aircraft
Category:1930s United States military transport aircraft
Category:Aircraft first flown in 1937
Category:Twin piston-engined tractor aircraft
Category:Aircraft with retractable conventional landing gear