World Library  
Flag as Inappropriate
Email this Article

Leading-edge extension

Article Id: WHEBN0000237737
Reproduction Date:

Title: Leading-edge extension  
Author: World Heritage Encyclopedia
Language: English
Subject: Droop (aeronautics), AAM-5 (Japanese missile), Chengdu J-20, Lockheed SR-71 Blackbird, McDonnell Douglas AV-8B Harrier II
Collection: Aerodynamics, Aerospace Engineering, Aircraft Wing Components, Aircraft Wing Design
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Leading-edge extension

Aircraft wing leading edge extensions - annotated

A leading-edge extension is a small extension to an aircraft wing surface, forward of the leading edge. The primary reason for adding an extension is to improve the airflow at high angles of attack and low airspeeds, to improve handling and delay the stall. A dog tooth can also improve airflow and reduce drag at higher speeds.

Contents

  • Leading-edge slat 1
  • Dogtooth extension 2
  • Leading-edge cuff 3
  • Leading-edge root extension 4
  • See also 5
  • References 6

Leading-edge slat

Slats deployed on an Airbus A318-100

A Leading edge slat is an aerodynamic surface running spanwise just ahead of the wing leading edge. It creates a leading edge slot between the slat and wing which directs air over the wing surface, helping to maintain smooth airflow at low speeds and high angles of attack. This delays the stall, allowing the aircraft to fly at a higher angle of attack. Slats may be made fixed, or retractable in normal flight to minimize drag.

Dogtooth extension

Dog tooth on the wing of a Hawker Hunter

A dogtooth is a small, sharp zig-zag break in the leading edge of a wing. It is usually used on a swept wing, to generate a vortex flow field to prevent separated flow from progressing outboard at high angle of attack.[1] The effect is the same as a wing fence.[2] It can also be used on straight wings in a Drooped Leading Edge arrangement.

Where the dogtooth is added as an afterthought, as for example on the Hawker Hunter and some variants of the Quest Kodiak, the dogtooth is created by adding an extension to the outer section of the leading edge.

Leading-edge cuff

Experimental drooped leading-edge cuff on an American Aviation AA-1 Yankee

A Leading edge cuff (or wing cuff) is a fixed aerodynamic device employed on fixed-wing aircraft to introduce a sharp discontinuity in the leading edge of the wing in the same way as as a dogtooth. It also typically has a slightly drooped leading edge to improve low-speed characteristics.

Leading-edge root extension

Condensation vortex flows along the LERX of an F/A-18

A leading-edge root extension (LERX) is a small fillet, typically roughly triangular in shape, running forward from the leading edge of the wing root to a point along the fuselage. These are often called simply leading-edge extensions (LEX), although they are not the only kind. To avoid ambiguity, this article uses the term LERX.

On a modern fighter aircraft LERX induce controlled airflow over the wing at high angles of attack, so delaying the stall and consequent loss of lift. In cruising flight the effect of the LERX is minimal. However at high angles of attack, as often encountered in a dog fight or during takeoff and landing, the LERX generates a high-speed vortex that attaches to the top of the wing. The vortex action maintains a smooth airflow over the wing surface well past the normal stall point at which the airflow would otherwise break up, thus sustaining lift at very high angles.

LERX were first used on the Northrop F-5 "Freedom fighter" which flew in 1959,[3] and have since become commonplace on many combat aircraft. The F/A-18 Hornet has especially large examples, as does the Sukhoi Su-27. The Su-27 LERX help make some advanced maneuvers possible, such as the Pugachev's Cobra, the Cobra Turn and the Kulbit.

A long, narrow sideways extension to the fuselage, attached in this position, is an example of a chine.

See also

References

  1. ^ Effects of Wing-Leading-Edge Modifications on a Full-Scale, Low-Wing General Aviation Airplane, Nasa TP 2011
  2. ^ A Two-seat Gnat Development for the R.A.F. Flight 1959
  3. ^ Green, W. and Swanborough, G.; The complete book of fighters, Salamander, 1994
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.