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Can a Bell-lift distribution without a rudder has higher overall efficiency (L/D) then current gliders, if the wingspan is not limited?

(Is it really possible that most of aerospace engineers don't understand the essence of Al Bowers' PRANDTL project? What is stopping the aero-industry from accepting his "new" design ideas? Is he wrong, or do they not want the risk of an unproven concept?)

AL Bowers say at 13:20 that Bell distribution increase L/D ratio by 12.5% ! ?

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  • $\begingroup$ One (undoubtedly among many) forums where you'll find some discussion on Al Bower's work is rcgroups.com . Do a search on the entire site using "Al Bowers" or other relevant terms. $\endgroup$
    – quiet flyer
    Jan 12, 2021 at 15:04
  • $\begingroup$ Related ASE question -- aviation.stackexchange.com/q/77662/34686 $\endgroup$
    – quiet flyer
    Jan 12, 2021 at 15:06

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Try to fly fast and you will see who hasn't understood the concept.

Just one datapoint: The lack of a rudder might be acceptable in a glider (but Heinz Scheidhauer, the pilot with most experience on Horten gliders, clearly said that at high speed the Horten gliders would be directionally indifferent) but not in powered flight. The fatal crash of the Ho-IX V2 can be attributed to loss of directional control after one engine failed.

On the SB-13 the vertical was replaced by two winglets which gave sufficient directional stability. However, when operating the plane, we often wished it had a conventional tail. Flight testing showed no clear advantage over current standard class gliders but operational restrictions were many.

All flying wings are susceptible to flutter because of their low pitch damping. In some Horten designs, flutter would limit the speed range at both ends.

Next: The low pitch stability forces you to use airfoils with low pitching moments. Trailing edge flaps can only be used in a very limited way, nowhere near what is usual on airliners. This limits the speed range almost as much as flutter does already.

And concerning the bell lift distribution: That lesson has been learned since maybe 70 years. Just look at the actual planforms: They are not elliptic and have little lift towards the tips.

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  • $\begingroup$ @EBV821 Talk is cheap. When you want to see how well flying wings cope with the sound barrier, just look at the DH-108. $\endgroup$
    – Peter Kämpf
    Jan 13, 2021 at 8:27
  • $\begingroup$ @EBV821 I do agree that Prandtl's ideas are correct but I don't agree that they have been forgotten and rediscovered by him. I also don't agree that flying wings make a viable configuration for everyday airplanes. $\endgroup$
    – Peter Kämpf
    Jan 13, 2021 at 15:51
  • $\begingroup$ @EBV821 Of course the Hortens knew about it and used this fact to avoid a vertical. And please don't think for a moment that the experts in big companies would not have known this, too, since maybe 70 years. Boeing studied the Horten IV extensively when they started to build swept wings. $\endgroup$
    – Peter Kämpf
    Jan 14, 2021 at 8:09

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