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Thread: A flying wing pusher airplane design

  1. #1

    A flying wing pusher airplane design

    Hello all, This is a two-place airplane I've designed. It will use a 3-axis artificial stabilization system. The wing airfoil is not reflexed. The horizontal stabilizer provides the down force to counteract section pitching moment. I welcome your comments.
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  2. #2

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    I would be concerned about the horizontal tail down load creating wing tip positive twist couple. Could cause tip stall or worse.

  3. #3
    Thank you for pointing that out, Bill.
    The wing would need to be stiff in torsion.

  4. #4

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    hey Dave,
    Flying wings are trickey, Historically there have been several of them but they didnt do too well in the market.Before spending alot of money on this make sure you study past models. Personaly i like them but i dont want to own one,
    Jeff

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    Takeoff can be tricky. Read the Sport Aviation archives for "Dean Delta". A fatal crash on first takeoff. The thrust on takeoff pushed the nose down. It wouldn't rotate with no prop blast over the tail. But when the pilot aborted at high speed, the lack of nose down thrust then caused a pitch up and it went out of control.

  6. #6
    I appreciate your excellent input, Bill and Birdman! All important points. Two features that make an airplane suitable for low time pilots is plenty of stability, and low stalling speed. Two problems with flying wings is lack of stability, and the reflexed airfoil which reduces lift coefficient. I've been impressed, however, with the model radio control flying wings I've seen, which are steady and easy to fly. They use a gyroscopic stabilization system adapted from quadcopters (drones).

  7. #7

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    Are these models not reflexed?
    I have flown some of these powered wings brought out by others. I don't know if they have artificial stability. They were all hand launched with no wheels so the problems of takeoff was not a factor.

  8. #8
    I assume the airfoil would have to be reflexed on these model wings to decrease center of pressure travel but have not examined it up close. One disadvantage of a conventional flying wing is that up elevon is needed to flare for landing. This changes the shape of the wing in an unfavorable way just when maximum lift is needed. Hence I mounted the elevons on horizontal stabilizers. I can further increase the lift coefficient by moving the CG back because it reduces stabilizer down force. The elevator servo would need to be very fast in such a system because of the short period of pitch oscillations.

    All the flying wings, and most of the conventional fixed wing model airplanes I've seen use artificial 3-axis stabilization. It's becoming almost a standard feature.

  9. #9

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    I doubt these models have abandoned natural stability. They likely still have a normal positive stability margin.
    But I will do some inspection at the RC field.
    Operating a full size aircraft without natural stability is beyond my comfort zone.

  10. #10
    FlyingRon's Avatar
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    First off, you do not have a flying wing. A flying wing is a design without a prominent fuselage. You don't even appear to have a "tail-less" aircraft. Just a novel design to hang the tail off the wing tips.

    What I see of challenges here:

    As mentioned, the structure needed to support the yaw and pitch movements way out on the end of the wings like that (there's good reason that they normally attach elevators to the fuselage).

    The pitch control is going to be interesting. It appears you have the CG way ahead of the center of lift. This is going to mean you're going to have to generate a lot of downforce with your "elevator winglets" to keep the nose horizontal. This is going to decrease efficiency as well.

    Configuations like this often have some fun with aerodynamic things like flutter due to the flexibility of the components and the fact that you've got parts of them likely in the slipstream of the pusher.

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