World Library  
Flag as Inappropriate
Email this Article

Wing fence

Article Id: WHEBN0002622241
Reproduction Date:

Title: Wing fence  
Author: World Heritage Encyclopedia
Language: English
Subject: Vortilon, DFS 346, Bréguet Br 900 Louisette, Lavochkin La-190, Fritz X
Collection: Aircraft Wing Components
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Wing fence

The MiG-17 included prominent wing fences
Close up of the wing fences of an East German Air Force Su-22

Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Often seen on swept-wing aircraft, wing fences are flat plates fixed to the upper surfaces parallel to the airflow, typically wrapping around the leading edge. By obstructing span-wise airflow along the wing, they prevent the entire wing from stalling at once, as opposed to wingtip devices, which increase aerodynamic efficiency by seeking to recover wing vortex energy.

As a swept-wing aircraft slows toward the stall speed of the wing, the angle of the leading edge forces some of the airflow sidewise, toward the wing tip. This process is progressive, airflow near the middle of the wing is affected not only by the leading edge angle, but also the spanwise airflow from the wing root. At the wing tip the airflow can end up being almost all spanwise, as opposed to front-to-back over the wing, meaning that the effective airspeed drops well below the stall. Because the geometry of swept wings typically places the wingtips of an aircraft aft of its center of gravity, lift generated at the wingtips tends to create a nose-down pitching moment. When the wingtips stall, both the lift and the associated nose-down pitching moment rapidly diminish. The loss of the nose-down pitching moment leaves the previously balanced aircraft with a net nose-up pitching moment. This forces the nose of the aircraft up, increasing the angle of attack and leading to stall over a greater portion of the wing. The result is a rapid and powerful pitch-up followed by a complete stall, a difficult situation for a pilot to recover from.[1] The "Sabre dance" (which caused many F-100 Super Sabres to crash) is a notable example of this behavior.

A Polish Sukhoi Su-20, showing the wing fences in relation to its wings

Wing fences delay, or eliminate, this effect by preventing the spanwise flow from moving too far along the wing and gaining speed. When meeting the fence, the air is directed back over the wing surface. Similar solutions included a notch in the leading edge, as seen on the Avro Arrow, or the use of slats, as on the earlier versions of the F-86. Slats can act as fences directly, in the form of their actuators, but also reduce the problem by improving the angle of attack response of the wing and moving the stall point to a lower speed.[1]

Wolfgang Liebe, who is generally credited with inventing wing fences, filed a patent[2] for it in 1938 while working on the Messerschmitt BF 109B. After World War II, Soviet military aircraft designers became known for their habit of using wing fences, using them on aircraft as varied as Mikoyan MiG-15s and Tupolev Tu-22Ms.

See also

References

  1. ^ a b Hurt, H. H. Jr., "NAVAIR 00-80T-80, Aerodynamics for Naval Aviators". Naval Air Systems Command, 1965, p. 86. at faa.gov
  2. ^ (German) DE 700625  "Vorrichtung zum Verhindern der Ausbreitung von Strömungsstörungen an Flugzeugflügeln" filed on September 27, 1938.

External links

  • Essay on wing fences at B2streamlines.com PDF
  • Wing Vortex Devices at aerospaceweb.org
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.