Blended wing body

A blended wing body (BWB), also known as blended body, hybrid wing body (HWB) or a lifting aerofoil fuselage,[1] is a fixed-wing aircraft having no clear dividing line between the wings and the main body of the craft.[2] The aircraft has distinct wing and body structures, which are smoothly blended together with no clear dividing line.[3] 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.

A rendering of the US Air Force blended wing body aircraft project

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
The N3-X NASA concept

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 and McDonnell Douglas 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.[4]: 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.[5] Studies suggested that a BWB airliner carrying from 450 to 800 passengers could achieve fuel savings of over 20 percent.[4]: 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.[6]

The N3-X NASA concept uses a number of superconducting electric motors to drive the distributed fans to lower the fuel burn, emissions, and noise. The power to drive these electric fans is generated by two wingtip-mounted gas-turbine-driven superconducting electric generators. This idea for a possible future aircraft is called a "hybrid wing body" or sometimes a blended wing body. In this design, the wing blends seamlessly into the body of the aircraft, which makes it extremely aerodynamic and holds great promise for dramatic reductions in fuel consumption, noise and emissions. NASA develops concepts like these to test in computer simulations and as models in wind tunnels to prove whether the possible benefits would actually occur.

2020s

In 2020, Airbus presented a BWB concept as part of its ZEROe initiative and demonstrated a small-scale aircraft.[7][8] In 2022, Bombardier announced its EcoJet project.[8][9] In 2023, California startup JetZero announced its Z5 project, designed to carry 250 passengers, targeting the New Midmarket Airplane category, expecting to use existing CFM International LEAP or Pratt & Whitney PW1000G 35,000 lbf (160 kN) engines.[10][11] In August 2023, the U.S. Air Force announced a $235-million contract awarded over a four-year period to JetZero, culminating in first flight of the full-scale demonstrator by the first quarter of 2027. The goal of the contract is to demonstrate the capabilities of BWB technology, giving the Department of Defense and commercial industry more options for their future air platforms.[12][13]

Characteristics

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.[14]

The BWB form minimizes 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.[15]

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.[16]

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).

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 theater-style instead of tubular. This imposes inherent limits on the number of exit doors.[21][22]
  • It has been suggested that BWB interiors would be windowless;[23] more recent information shows that windows may be positioned differently but involve the same weight penalties as a conventional aircraft.[24]
  • It has been suggested that passengers at the edges of the cabin may feel uncomfortable during wing roll;[23] however, passengers in large conventional aircraft like the 777 are equally susceptible to such roll.[24]
  • The center wingbox needs to be tall to be used as a passenger cabin, requiring a larger wing span to balance out.[25]
  • A BWB has more empty weight for a given payload, and may not be economical for short missions of around four or fewer hours.[25]
  • A larger wing span may be incompatible with some airport infrastructure, requiring folding wings similar to the Boeing 777X.
  • 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.[25]
  • Pitch control and lift capability at low speed have presented challenges for blended-wing designs. JetZero has proposed a novel landing gear design to address these issues for its Z-5 BWB concept.[10]

List of blended wing body aircraft
The Northrop BAT UAV in flight from below
TypeCountryClassRoleDateStatusNo.Notes
Airbus MavericMultinationalUAVExperimental2019Prototype1[26][27]
Boeing X-45USUAVExperimental2002Prototype2
Boeing X-48 (C)USUAVExperimental2013Prototype2Two engine
Boeing X-48 (B)USUAVExperimental2007Prototype2Three engine
Lockheed A-12, M-21 and YF-12USJetReconnaissance1962Production18YF-12 was a prototype interceptor
Lockheed SR-71 BlackbirdUSJetReconnaissance1964Production32
Northrop Grumman BatUSProp/electricReconnaissance2006Production10
McDonnell XP-67USPropellerFighter1944Prototype1Aerofoil profile maintained throughout.
McDonnell / NASA BWB-17USUAVExperimental1997Prototype1
Miles M.30UKPropellerExperimental1942Prototype1
Rockwell B-1 LancerUSJetBomber1974Production104Variable-sweep wing
Tupolev Tu-160USSRJetBomber1981Production36Variable-sweep wing
Tupolev Tu-404RussiaPropellerAirliner1991Project0One of two alternatives studied
Westland DreadnoughtUKPropellerTransport1924Prototype1Mail 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.[28] 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.[29] 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.[30][31][32]

See also

References
  1. Wragg, David W. (1973). A Dictionary of Aviation (first ed.). Osprey. p. 177. ISBN 978-0-85045-163-4.
  2. Thomas, Russell H.; Burley, Casey L.; Olson, Erik D. (2010). "Hybrid Wing Body Aircraft System Noise Assessment With Propulsion Airframe Aeroacoustic Experiments" (PDF). Retrieved 26 January 2013. PresentationArchived 2013-05-16 at the Wayback Machine
  3. Crane, Dale. Dictionary of Aeronautical Terms, third edition. Newcastle, Washington: Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2. p. 224.
  4. Liebeck, R.H. (January–February 2004). "Design of the Blended Wing Body Subsonic Transport" (PDF). Journal of Aircraft. 41 (1): 10–25. doi:10.2514/1.9084.
  5. "A flight toward the future." Archived December 4, 2012, at the Wayback Machine Boeing, August 7, 2012 Retrieved: November 23, 2012.
  6. Reim, Garrett (11 February 2020). "Airbus studies blended-wing airliner designs to slash fuel burn". Flight Global.
  7. "Airbus reveals new zero emission concept aircraft" (Press release). Airbus. 21 September 2020.
  8. Kevin Michaels (June 1, 2023). "Opinion: Why It Is Time For The Blended Wing Body". Aviation Week.
  9. Verdon, Michael (May 30, 2023). "Bombardier's New Blended-Wing 'EcoJet' Cuts Emissions by 50%—and It's Hitting the Skies Soon". Robb Report.
  10. Norris, Guy; Warwick, Graham (21 April 2023). "JetZero Unveils Midmarket Airliner And Air Force Tanker BWB Plan". aviationweek.com. Retrieved 17 August 2023.
  11. Roza, David (May 2, 2023). "As USAF Considers a Blended-Wing Body Tanker, New Startup Reveals Its Concept". Air & Space Forces Magazine.
  12. Marrow, Michael (16 August 2023). "Air Force picks startup JetZero to build blended wing body demonstrator". breakingdefense.com. Retrieved 17 August 2023.
  13. Alcock, Charles (16 August 2023). "JetZero's blended-wing body aircraft boosted by U.S. Air Force contract". futureflight.aero. Retrieved 17 August 2023.
  14. Bullis, Kevin (January 24, 2013). "NASA has demonstrated a manufacturing breakthrough that will allow hybrid wing aircraft to be scaled up". MIT Technology Review.
  15. Braukus, Michael; Barnstorff, Kathy (Jan 7, 2013). "NASA's Green Aviation Research Throttles Up Into Second Gear". NASA. Retrieved Jan 26, 2013.
  16. Warwick, Graham (Aug 22, 2016). "Finding Ultra-Efficient Designs For Smaller Airliners". Aviation Week & Space Technology.
  17. Warwick, Graham (21 May 2007). "Boeing works with airlines on commercial blended wing body freighter". Flight Global. Retrieved 2023-02-12.
  18. "Blended Wing Body Fact Sheet". NASA. Retrieved 2021-05-17.
  19. Finnerty, Ryan (2022-10-12). "US Air Force to test blended-wing logistics aircraft by 2027". Flight Global. Retrieved 2023-02-12.
  20. Warwick, Graham (Jan 12, 2013). "Hear This – The BWB is Quiet!". Aviation Week.
  21. Galea, E. R.; Filippidis, L.; Wang, Z.; Lawrence, P. J.; Ewer, J. (2011). "Evacuation Analysis of 1000+ Seat Blended Wing Body Aircraft Configurations: Computer Simulations and Full-scale Evacuation Experiment". Pedestrian and Evacuation Dynamics: 151–61. doi:10.1007/978-1-4419-9725-8_14. ISBN 978-1-4419-9724-1. S2CID 55673992.
  22. Galea, Ed. "Evacuation analysis of 1000+ seat Blended Wing Body aircraft configurations". Evacmod (video). Retrieved August 25, 2015.
  23. "Boeing not convinced by blended wing aircraft design". Institution of Mechanical Engineers. June 16, 2015.
  24. Page, Mark (2018-09-14). "Single-aisle Airliner Disruption with a single-deck blended-wing-body" (PDF). ICAS. Archived (PDF) from the original on 2018-12-20.
  25. "Don't look for commercial BWB airplane any time soon, says Boeing's future airplanes head". Leeham News. April 3, 2018.
  26. "Airbus reveals its blended wing aircraft demonstrator". Airbus (Press release). Singapore. 11 February 2020. Retrieved 2023-02-12.
  27. Caroline Delbert (2020-02-13). "Will People Fly In This 'Blended Wing' Airplane? Airbus Built a Prototype To Find Out". Popular Mechanics. Retrieved 2023-02-12.
  28. "The Future of Flight". Popular Science. Vol. 263, no. 5. Bonnier Corporation. November 2003. pp. 83–86.
  29. "Future Flight: A Gallery of the Next Century in Aviation". Popular Science. 2003-10-16. Retrieved 2023-02-12.
  30. "New Boeing 797 Giant "Blended Wing" Passenger Airliner-Fiction!". TruthOrFiction.com. March 17, 2015.
  31. Christensen, Brett M. (April 19, 2012). "Boeing 797 Hoax". Hoax-Slayer. Archived from the original on 2012-04-23.
  32. Baseler, Randy. "Air mail." Boeing blogs: Randy's Journal, November 1, 2006. Retrieved: November 22, 2012.

Further reading
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