I was reading a description of the Boeing X-45 that described it as having "lambda wings." What is a lambda wing and why is it called that?


Indeed, it is due to resemblance with Greek letter 'lambda', though not the capital one ($ \Lambda $), but the small one: $ \lambda $.

I am attaching a pic of X-45 with me drawing a lambda over it. Typically, the wing has two taper ratios. The inboard wing tapers heavily, corresponding to legs of small lambda, and the outboard wing tapers slightly or do not taper at all.

X-45 with Lambda drawn over

Other examples include B-2 bomber: B2 bomber from below

  • $\begingroup$ This answer seems to be correct. Related link that could be included in answer : fas.org/man/dod-101/sys/ac/docs/fatereport/sld034.htm . Google "lambda wing" for more. However it's not impossible that at one time in the past, the term would have been applied to the wing of the English Electric Lightning, etc. $\endgroup$ – quiet flyer Jul 9 '19 at 17:58
  • $\begingroup$ I must be missing something. You stated, "a pic of X-45 with me drawing a lambda over it". Unless it's a GIF that's supposed to actively show you drawing a lambda and whatever mechanism that's supposed to show GIFs is disabled in my browser, I'm not seeing anything drawn over the X-45A. $\endgroup$ – FreeMan Jul 9 '19 at 18:15
  • $\begingroup$ @FreeMan - notice the odd black mark on one side? $\endgroup$ – quiet flyer Jul 9 '19 at 18:42
  • $\begingroup$ Wow. No, I completely missed that. Hangs head in shame $\endgroup$ – FreeMan Jul 9 '19 at 19:15
  • $\begingroup$ It's ok! Really... $\endgroup$ – quiet flyer Jul 9 '19 at 19:19

It's because the shape of the wing resembles the uppercase Greek letter lambda with the leading and trailing edges having the same sweep angle.

enter image description here

  • 1
    $\begingroup$ What makes it different from simply “swept wings” though? $\endgroup$ – Jan Hudec Mar 30 '19 at 13:27
  • $\begingroup$ Here's a presentation from Lockheed Martin: fas.org/man/dod-101/sys/ac/docs/fatereport/sld035.htm $\endgroup$ – IconDaemon Mar 30 '19 at 13:50
  • $\begingroup$ I see—the confusing point is that there are actually two very different X-45 concepts. The X-45A has swept wing and fuselage with pronounced chines, while the X-45B/C is a flying wing. According to the presentation, the term applies to the later. $\endgroup$ – Jan Hudec Mar 30 '19 at 13:55
  • $\begingroup$ I had read through that presentation before I posted the question, but it isn’t at all clear what distinguishes a “lambda” planform from any other swept wing. $\endgroup$ – TomMcW Mar 31 '19 at 21:21
  • $\begingroup$ I’m no aeronautical designer, just a dude who knows why that particular wing shape is called ‘lambda’. An educated guess is that a ‘swept wing’ is a more generic term for wings of a configuration with a swept leading and trailing edges unlike a Piper Cub, for example, which has straight leading and trailing edge. There may be several distinct ‘swept wing’ configurations with curved leading and/or trailing edges, but the ‘lambda’ configuration is unique, with straight leading and trailing edges. Again, I’m no expert, and would like to know if there is any deeper explanation. $\endgroup$ – IconDaemon Apr 1 '19 at 9:31

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