Lateral Damping: Any actual flying wing pilots on here?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Aerowerx, Sep 13, 2019.

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  1. Sep 13, 2019 #1

    Aerowerx

    Aerowerx

    Aerowerx

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    For quite some time I have had a flying wing design on the back burner. Every so often I stir the pot to keep it from boiling over.;)

    I have seen the mil-spec for acceptable handling characteristics and have a feel for the required amount of damping for lateral and longitudinal stability. In my virtual tests, longitudinal is not a problem.

    What I am wondering is if there is anyone on here that has flown a tailless flying wing. How did it behave? Did the nose tend to wander back and forth? Was it "disconcerting"? Any other strange quirks?

    If you answer, it would be highly useful to know the type of aircraft. And I am including hang gliders and trikes in this, besides the Mitchel wings and Kasper wings, Opal, Marske designs, etc. A report on the newer Horten designs would be great!
     
  2. Sep 13, 2019 #2

    henryk

    henryk

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    -see
    https://kasperwing.com/personal-videos/
     
  3. Sep 14, 2019 #3

    Aerowerx

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    Thanks, henryk, but it is hard to tell from the video how it is behaving with respect to the lateral stability.

    I am trying to determine just what effect the lateral damping has on the "feel".
     
  4. Sep 14, 2019 #4

    jedi

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    I have some limited time in a Mitchel B-10, a little more in a Kasper Wing Ultralight (AKA Cascade Ultra Light), early Rogallo hang gliders and limited time in modern hang gliders, and considerable trike WSC Light Sport and earlier Ultra Light Trainers and Ultra Light trikes.

    The following is my attempt to answer the above questions based on my experience not on any facts
    or accepted theory.

    In all of the above I have not noticed any issues with "the nose tend to wander back and forth" or what I would call "Lateral Damping". I assume by lateral damping issues you would be referring to a yawing oscillation that continues for several cycles before being damped to zero.

    This is a characteristic in gliders that are known to have a large moment of inertia about the vertical axis (due to the long heavy wings) and minimum vertical stabilizer tail volume to reduce drag. It is an issue in training but pilots learn to control the aircraft and it is no longer an issue.

    What is an issue with WSC trikes and hang gliders is a tendency to Dutch Roll at high speed. This is caused by the combination of yaw/roll coupling and inertia about the vertical axis. The yaw roll couple results from excessive dihedral and limited vertical stabilizer. I have not noticed a dutch roll issue in the B-10 or the Cascade Ultralights flying wings. I expect it would be an issue at higher speeds outside the operating envelope. The Mitchel Wing has had problems reported with an instability of the tip rudders at high speed.

    The WSC dutch roll becomes an issue as the wing is tuned for efficient high speed flight. The Cosmos topless was a good example of this with the top speed being limited by the ability to limit the dutch roll.

    Dutch roll is an issue in jet transports. One B-707 hull loss was attributed to dutch roll training. I have considerable dutch roll experience in a B-727 simulator.

    The V tail Bonanza is known to have a mild dutch roll tendency.

    I hope this helps.
     
  5. Sep 14, 2019 #5

    Aerowerx

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    Thanks, Jedi! Just the type of answer I was looking for.

    And yes, I was referring to lateral damping. I have been doing virtual testing in XFLR5. In the stability analysis there are 4 lateral modes. One of them is Dutch Roll.

    Now I can look at the ones you mentioned and figure out their parameters.
     
  6. Sep 14, 2019 #6

    jedi

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    Glad to be of assistance. I would like to help more and follow your studies. Keep us informed of your work.
     
  7. Sep 14, 2019 #7

    Aerowerx

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    I haven't done anything serious yet. This is just something that I work on whenever I feel like.

    But I am convinced that it is possible to build a flying wing that is easy to fly for the average pilot and does not have the CG range issues typically associated with tailless aircraft (find the empty CG position with desired static margin, and put the seat at that location!).
     
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  8. Sep 15, 2019 #8

    Aesquire

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    My Wills Wing Duck late 1980s ( But still "modern" ) hang glider would Dutch roll at high speed , but only as a PIO if I clenched up on the controls. Initiating a slight bank and just waiting for it to stabilize stopped it. The phenomenon is also called Wing Walking.

    I never had the problem while turning even at Max speed, only on straight glides, so my assumption was the glider was lagging behind my small corrections, aka, I got out of sync with the roll response.
     
  9. Sep 15, 2019 #9

    jedi

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    The problem with Dutch Roll is always the frequency. If the period is long enough the pilot just flies the airplane. As the frequency gets down to a second or less the pilot gets behind the curve and the Dutch Roll takes over. There is a middle ground where the solution is just "do nothing" and there is no problem. Shorten the period even more or increase the amplitude, then things get much more exciting.
     
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  10. Sep 16, 2019 #10

    Aerowerx

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    Yes, I am aware of that.

    I was looking for actual pilot reports for actual real world tailless aircraft. Which ones are "disturbing" to fly? Which ones are docile? Any fly hands off, at least for a few minutes? Then I can look at their design parameters and correlate to what I am seeing in my virtual wind tunnel.
     
  11. Sep 16, 2019 #11

    Topaz

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    There are some pireps online for the AV-36, Pioneer II, and some other tailless airplanes, especially gliders. I recall a rather extensive pirep for the Fauvel Choucas powerplane, as well. I'm typing this on my phone and I don't have links handy. A search should turn those up.

    I know you have (I think you have) a copy of Tailless Aircraft in Theory and Practice, and there are several pireps in the book, with analysis by Dr. Nickel. Those, if I recall, focus on pitch-axis flight properties, but should be helpful nonetheless.

    Tailless designs are rare enough that it'll be challenging to come up with more than a handlful of first-hand pireps on a forum like HBA, especially for a narrow slice of handline qualities like this.

    In the end, you'll need to have pretty "normal" handling qualities whether your airplane has a tail or not, and those can be calculated adequately with the design resources available.
     

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