“As a supplement to my recent piece on the Tejas program, Hush-Kit have asked me to contribute an item about leading-edge vortex controllers (LEVCON) on the Tejas, seeking to explain what these are, how they work, and why they might be used on Tejas. As explained in my previous article, this piece is from an outsider’s perspective, but in this case, from the background of an aerodynamics expert experienced in combat aircraft performance and configuration design.
I’m going to write about LEVCONs in the context of the Navy variant of Tejas, and seek to explain why they are being used on that aircraft. The picture below shows the Navy version of Tejas in its recent land-based arrested landing trials, and the second picture provides a clear view of the LEVCON behind some of the trials team.
To understand LEVCON, and their application to Tejas, it is first necessary to discuss the advantages and disadvantages of delta wing planforms for combat aircraft.
Delta Wings – Advantages
In the context of supersonic aircraft, the delta wing is an attractive design option. The key source of drag in supersonic flight is wave drag. Wave drag arises as a consequence of the pressure distribution on wing and body surfaces in supersonic flows. Wave drag is extremely sensitive to the thickness to chord ratio of the wing, and also to leading-edge radius. In aeronautics, the thickness-to-chord ratio, compares the maximum vertical thickness of a wing to its chord (the distance from the front to the back of a wing).
A thick wing, with a rounded leading edge, will have a very high wave drag if it experiences transonic or supersonic flows. In addition, wing sweep reduces the local mach number and delays the occurrence of wave drag in transonic flight. This is why fast aircraft tend to have highly swept wings.
From this brief discussion, some of the advantages of a delta wing planform for a supersonic fighter aircraft become apparent. The delta planform offers the possibility of using a low thickness to chord ratio wing, which simultaneously provides good wing area