Vortilon is a contraction of VORTex and pYLON words (generating vortices as a leading-edge engine pylon does).
Vortilons consist of one or more flat plates attached to the underside of the wing near its leading edge, aligned with the flight direction. When the speed is reduced and the aircraft approaches stall, the local flow at the leading edge is diverted outwards; this spanwise component of velocity around the vortilon creates a vortex streamed around the top surface, which energises the boundary layer. A more turbulent boundary layer, in turn, delays the local flow separation.
Vortilons are often used to improve low-speed aileron performance, thereby increasing resistance to spin. They can be used as an alternative to wing fences, which also restrict airflow along the span of the wing. Vortilons only stream vortices at high angles of attack and produce less drag at higher speeds than wing fences. Pylons used to mount jet engines under the wing produce a similar effect.
The occurrence of span-wise flow at high angles of attack, such as observed on swept wings, is an essential requirement for vortilons to become effective. According to Burt Rutan, vortilons installed on straight wings would not have any effect.
- Rutan VariEze, replacing leading edge cuffs (1984)
- Rutan Long-EZ
- BAe 125 1000 series
- Hawker 800XP
- Embraer ERJ 145 family
- Learjet 45
- Aériane Swift
- "Unicom". Flying: 75. July 2002. Retrieved 2011-10-07.
- Raymer, Daniel P. (1999). "8.2 Aerodynamic Considerations in Configuration Layout". Aircraft Design: A Conceptual Approach (3rd ed.). Reston, Virginia: American Institute of Aeronautics and Astronautics. p. 183. ISBN 1-56347-281-3.
- McClellan, J. Mac (November 2002). "Hawker 800XP". Flying: 75. Retrieved 2011-10-07.
- Barnard, R.H.; Philpott, D.R. (2010). "Boundary layer and stalling problems on swept wings". Aircraft Flight (4th ed.). Harlow, England: Prentice Hall. p. 75. ISBN 978-0-273-73098-9.
- McClellan, J. Mac (February 1993). "BAE 1000 Lifts Hawker Name to New Heights". Flying: 88. Retrieved 2011-10-07.
- "The DC-9 and the Deep Stall". FLIGHT International: 442. 25 March 1965. Retrieved 2011-10-07.
- Vortilons for Variezes, The canard pusher, n°42, October 1984
- Norris, Guy; Wagner, Mark (1999). Douglas Airliners. Oceola, Wisconsin: MBI Publishing Company. p. 24.
- Shevell, Richard S.; Schaufele, Roger D. (November–December 1966). "Aerodynamic Design Features of the DC-9". Journal of Aircraft 3 (6): 515–523.
- Smith, Steve. "Resources for learning about vortilons". NASA Quest. Retrieved 2011-10-07.
- Wing Vortex Devices from Aerospaceweb.org explains vortilons and other vortex-generating wing appliances