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Blended wing body

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Computer-generated model of the Boeing X-48
NASA's prototype of a Blended Wing aircraft

A blended wing body (BWB), also known as blended body or hybrid wing body (HWB), is a fixed-wing aircraft having no clear dividing line between the wings and the main body of the craft.[1] The aircraft has distinct wing and body structures, which are smoothly blended together with no clear dividing line.[2] This contrasts with a flying wing, which has no distinct fuselage, and a lifting body, which has no distinct wings. A BWB design may or may not be tailless.

The main advantage of the BWB is to reduce wetted area and the accompanying form drag associated with a conventional wing-body junction. It may also be given a wide airfoil-shaped body, allowing the entire craft to generate lift and thus reducing the size and drag of the wings.

The BWB configuration is used for both aircraft and underwater gliders.

History

In the early 1920s Nicolas Woyevodsky developed a theory of the BWB and, following wind tunnel tests the Westland Dreadnought was built. It stalled on its first flight in 1924, severely injuring the pilot, and the project was cancelled. The idea was proposed again in the early 1940s for a Miles M.26 airliner project and the Miles M.30 "X Minor" research prototype was built to investigate it. The McDonnell XP-67 prototype interceptor also flew in 1944 but did not meet expectations.

NASA returned to the concept in the 1990s with an artificially stabilized 17-foot (5.2 m) model (6% scale) called BWB-17, built by Stanford University, which was flown in 1997 and showed good handling qualities.[3]: 16  From 2000 NASA went on to develop a remotely controlled research model with a 21-foot (6.4 m) wingspan.

NASA has also jointly explored BWB designs for the Boeing X-48 unmanned aerial vehicle.[4] Studies suggested that a BWB airliner carrying from 450 to 800 passengers could achieve fuel savings of over 20 percent.[3]: 21 

Airbus is studying a BWB design as a possible replacement for the A320neo family. A sub-scale model flew for the first time in June 2019 as part of the MAVERIC (Model Aircraft for Validation and Experimentation of Robust Innovative Controls) programme, which Airbus hopes will help it reduce CO2 emissions by up to 50% relative to 2005 levels.[5]

Characteristics

Spectrum of aircraft design concepts. From left to right: conventional airliner (Boeing 757), blended wing body (B-1 Lancer), flying wing with bulged fairings (B-2 Spirit), and almost clean flying wing (Northrop YB-49).

The BWB form minimises the total wetted area - the surface area of the aircraft skin, thus reducing skin drag to a minimum. It also creates a thickening of the wing root area, allowing a more efficient structure and reduced weight compared to a conventional craft. NASA also plans to integrate Ultra High Bypass (UHB) ratio jet engines with the hybrid wing body.[6]

The wide interior spaces created by the blending pose novel structural challenges. NASA has been studying foam-clad stitched-fabric carbon fiber composite skinning to create uninterrupted cabin space.[7]

A conventional tubular fuselage carries 12-13% of the total lift compared to 31-43% carried by the centerbody in a BWB, where an intermediate lifting-fuselage configuration better suited to narrowbody sized airliners would carry 25-32% for a 6.1% - 8.2% increase in fuel efficiency.[8]

Potential advantages

Potential disadvantages

  • Evacuating a BWB in an emergency could be a challenge. Because of the aircraft's shape, the seating layout would be theatre-style instead of tubular. This imposes inherent limits on the number of exit doors.[11][12]
  • Passengers may be unwilling to sit in windowless environments.[13]
  • Passengers sitting at the edges of the cabin may feel uncomfortable during wing roll.[13]
  • The centre wingbox needs to be tall to be used as a passenger cabin, requiring a larger wing span to balance out.[14]
  • A BWB has more empty weight for a given payload, and may not be economical for short missions of around four or fewer hours.[14]
  • A larger wing span may be incompatible with some airport infrastructure, and affect the quick loading of cargo, requiring a change in infrastructure.[14]
  • It is more expensive to modify the design to create differently-sized variants compared to a conventional fuselage and wing which can be stretched or shrunk easily.[14]

List of blended wing body aircraft

Type Country Class Role Date Status No. Notes
Airbus Maveric EU UAV Experimental 2019 Prototype 1 [15][16]
Boeing X-45 USA UAV Experimental 2002 Prototype 2
Boeing X-48 USA UAV Experimental 2007 Prototype 2
Lockheed A-12, M-21 and YF-12 US Jet Reconnaissance 1962 production 18 YF-12 was a prototype interceptor
Lockheed SR-71 Blackbird US Jet Reconnaissance 1964 production 32
McDonnell XP-67 USA Propeller Fighter 1944 Prototype 1 Aerofoil profile maintained throughout.
Miles M.30 UK Propeller Experimental 1942 Prototype 1
Rockwell B-1 Lancer USA Jet Bomber 1974 Production 104 Variable-sweep wing
Tupolev Tu-160 USSR Jet Bomber 1981 Production 36 Variable-sweep wing
Tupolev Tu-404 Russia Propeller Airliner 1991 Project 0 One of two alternatives studied
Westland Dreadnought UK Propeller Transport 1924 Prototype 1 Mail plane. Aerofoil profile maintained throughout.
Image of the "Boeing 797" from Popular Science, 2003

A concept photo of a blended wing body commercial aircraft appeared in the November 2003 issue of Popular Science magazine.[17] Artists Neill Blomkamp and Simon van de Lagemaat from The Embassy Visual Effects created the photo for the magazine using computer graphics software to depict the future of aviation and air travel.[18] In 2006 the image was used in an email hoax claiming that Boeing had developed a 1000-passenger jetliner (the "Boeing 797") with a "radical Blended Wing design" and Boeing refuted the claim.[19][20][21]

See also

References

  1. ^ a b Russell H. Thomas, Casey L. Burley and Erik D. Olson (2010). "Hybrid Wing Body Aircraft System Noise Assessment With Propulsion Airframe Aeroacoustic Experiments" (PDF). Retrieved 26 January 2013. Presentation Archived 2013-05-16 at the Wayback Machine
  2. ^ Crane, Dale. Dictionary of Aeronautical Terms, third edition. Newcastle, Washington: Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2. p. 224.
  3. ^ a b Liebeck, R.H. (January–February 2004). "Design of the Blended Wing Body Subsonic Transport". Journal of Aircraft. 41 (1): 10–25. doi:10.2514/1.9084.
  4. ^ "A flight toward the future." Archived December 4, 2012, at the Wayback Machine Boeing, August 7, 2012 Retrieved: November 23, 2012.
  5. ^ Reim, Garrett (11 February 2020). "Airbus studies blended-wing airliner designs to slash fuel burn". Flight Global.
  6. ^ Michael Braukus / Kathy Barnstorff (Jan 7, 2013). "NASA's Green Aviation Research Throttles Up Into Second Gear". NASA. Retrieved Jan 26, 2013.
  7. ^ Bullis, Kevin (January 24, 2013). "NASA has demonstrated a manufacturing breakthrough that will allow hybrid wing aircraft to be scaled up". MIT Technology Review.
  8. ^ a b Graham Warwick (Aug 22, 2016). "Finding Ultra-Efficient Designs For Smaller Airliners". Aviation Week & Space Technology.
  9. ^ Warwick, Graham. "Boeing works with airlines on commercial blended wing body freighter." Flight International, May 21, 2007.
  10. ^ Warwick, Graham (Jan 12, 2013). "Hear This - The BWB is Quiet!". Aviation Week.
  11. ^ E. R. Galea; L. Filippidis; Z. Wang; P. J. Lawrence; J. Ewer (2011). "Evacuation Analysis of 1000+ Seat Blended Wing Body Aircraft Configurations: Computer Simulations and Full-scale Evacuation Experiment". Pedestrian and Evacuation Dynamics. pp. 151–61. doi:10.1007/978-1-4419-9725-8_14. ISBN 978-1-4419-9724-1.
  12. ^ Galea, Ed. "Evacuation analysis of 1000+ seat Blended Wing Body aircraft configurations". evacmod.net (video). Retrieved August 25, 2015.
  13. ^ a b "Boeing not convinced by blended wing aircraft design". Institution of Mechanical Engineers. June 16, 2015.
  14. ^ a b c d "Don't look for commercial BWB airplane any time soon, says Boeing's future airplanes head". Leeham News. April 3, 2018.
  15. ^ "Airbus reveals its blended wing aircraft demonstrator", Airbus, 11 February 2020. (Retrieved 18 February 2020)
  16. ^ Caroline Delbert; "Will We One Day Fly in This 'Blended Wing' Airplane? Airbus Built a Prototype To Find Out", Popular Mechanics, 13 February 2020. (Retrieved 18 February 2020)
  17. ^ "Future of Flight." Popular Science, November 2003.
  18. ^ "Future Flight: A Gallery of the Next Century in Aviation." PopSci.com, October 15, 2003. Retrieved: November 22, 2012.
  19. ^ "New Boeing 797 Giant "Blended Wing" Passenger Airliner-Fiction!". TruthOrFiction.com. March 17, 2015.
  20. ^ Christensen, Brett M. "Boeing 797 Hoax" Hoax-Slayer, April 19, 2012. Retrieved: November 22, 2012.
  21. ^ Baseler, Randy. "Air mail." Boeing blogs: Randy's Journal, November 1, 2006. Retrieved: November 22, 2012.

Further reading

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