The Rolls Royce Ultrafan prototype has been in development for a few years and has usually been seen in the media with very distinctive curved leading edge design as such:

A: highly swept blades

However, this week (December 2022) RR have officially put it into testing, and has what appear to be more conventional looking blades:

B: less swept blades

Have they abandoned the curved set? or just trying several sets?

Source of images: Rolls Royce Ultrafan images

  • 1
    $\begingroup$ looks like the curve that defines leading edge is identical in both pictures, with scaled up curvature at swept forward tip location that makes the first image much more stunning $\endgroup$
    – user21228
    Dec 20, 2022 at 16:44
  • 6
    $\begingroup$ @qqjkztd They are completely different. $\endgroup$ Dec 20, 2022 at 16:56
  • 1
    $\begingroup$ I'm trying to change the images in the question to ones that were taken from the same angle to better highlight the differences; they're not the same blades at all. $\endgroup$ Dec 21, 2022 at 4:07
  • 7
    $\begingroup$ The problem with asking this sort of question about this sort of technology is that the designs and design choices are proprietary, and RR are unlikely to comment much. If pushed you might get a comment about the evolution of the design through testing and development, but what they won't tell you is that the curved leading edge is dramatically better aerodynamically, but impossible to manufacture in volume. Or the reverse. Information like that is not something they want to hand to their competitors. $\endgroup$ Dec 21, 2022 at 7:46
  • 1
    $\begingroup$ They've been running it on the benches.... centrifugal forces fairly quickly straightened out the artistic curves the PR folks had in. :-) [The above is not entirely in sarcasm - they probably have found having a blade which has a high degree of curvature along the aeroline and along the structural centre of rotation lines hasn't played as well as they'd hoped.] $\endgroup$
    – Amiga500
    Dec 21, 2022 at 13:41


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