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I am proposing a plane that has 2 short wings of the same size on either side of the fuselage (two in the front and two in the back). Rather than using the horizontal stabilizer to destroy lift, the wings in the back help create lift and adjust the pitch of the plane.

One problem that I thought of is the wingtip vortex created by the front wing hitting the back wings. I'm guessing this can be resolved by placing the back wings higher than the front wings (from a front view of the fuselage).

Could this work?

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  • $\begingroup$ By "work" do you mean fly or be more efficient than planes with single wings? $\endgroup$
    – Brinn Belyea
    Jun 7, 2015 at 1:35
  • $\begingroup$ I mean be able to fly. I'd assume that it would be more efficient. $\endgroup$
    – Ewen W.
    Jun 7, 2015 at 2:45
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    $\begingroup$ As per my answer, more and shorter wings -> less efficient. This is why gliders (most concerned with efficiency) have long wings. You need to minimise the ratio of end effects to middle of wing efficiency. $\endgroup$
    – GreenAsJade
    Jun 7, 2015 at 4:10
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    $\begingroup$ The "wing tip" vortex is not generated by the tip, but is a result of the wing downwash that is side-effect of producing lift. Since the wing affects air above and below it to height approximately equal to its span, the aft wing will fly in the downwash of the front wing no matter where you place it. $\endgroup$
    – Jan Hudec
    Jun 7, 2015 at 11:03
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    $\begingroup$ Note that horizontal stabilizer does not necessarily destroy lift or produce negative lift. If you're looking for unusual designs, think at Scaled composites' aircrafts. $\endgroup$
    – Manu H
    Jun 7, 2015 at 12:53

5 Answers 5

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What you are proposing is called a "tandem wing", and it's been done before. A brief search should produce more than enough research papers about the advantages and disadvantages of this particular design.

The near-complete absence of multiple-wing designs in modern aviation should be a hint that the design has issues. Unless you particularly need the advantages of the design more than the drawbacks, there's no particular reason to use it.

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    $\begingroup$ What are some disadvantages of the tandem wing? $\endgroup$
    – Ewen W.
    Jun 7, 2015 at 2:44
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    $\begingroup$ @EwenW. That would be an excellent question to post to this Stack :) $\endgroup$
    – Jae Carr
    Jun 7, 2015 at 5:09
  • $\begingroup$ @EwenW. "what are the advantages" might be a better question $\endgroup$
    – o0'.
    Aug 9, 2015 at 10:09
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It would be able to "work". Anything with a strong enough engine pointed in the right direction can fly :)

The question is how well it will work.

A significant issue is that the most of the problems with wings occur where they join to the fuse, and where they end. It's the middle part of the wing that works optimally. So if you half the length of your wings and double the number of them you are giving yourself massively increased end effects...

As mentioned in comments, the dynamics of stability are also more challenging when you have two main wings producing lift.

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    $\begingroup$ An additional problem is that the usual "main wing and stabilizing tailplane" configuration (where the tailplane produces negative lift in level flight) will naturally tend back towards level flight after a minor deviation in pitch, whereas having a fore and an aft wing that both lift would need additional arrangements for pitch stability. $\endgroup$
    – hmakholm left over Monica
    Jun 7, 2015 at 4:38
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    $\begingroup$ @HenningMakholm: Not quite. Just let the rear wing produce less lift per unit of area than the front wing, and the configuration is stable in the same way as a conventional configuration. If you desire a longer explanation, ask a new question. $\endgroup$
    – Peter Kämpf
    Jun 7, 2015 at 6:39
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    $\begingroup$ @PeterKämpf broadly speaking you just listed "additional arrangements" $\endgroup$
    – Federico
    Jun 7, 2015 at 8:05
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    $\begingroup$ You also want the front wing to stall before the rear wing. Otherwise the stall will be violently nose up and difficult to recover from. I think this is essential if you want to call the configuration flyable. That goes together with having the rear wing more lightly loaded as @Peter Kämpf says. $\endgroup$
    – Wirewrap
    Jun 7, 2015 at 11:00
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    $\begingroup$ That will depend entirely on the relative angles and dynamics of the wings. You could set it up so that the rear wing stalls first, which would be deadly... $\endgroup$
    – GreenAsJade
    Jun 7, 2015 at 13:12
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First the answer to your question: Yes, it can.

The probably most popular tandem wing was the French "Sky louse" (Pou du Ciel), a design from the 1930's that was built in countless variations.

https://2.bp.blogspot.com/-PXSUxLit1PU/U2_TxAVLmlI/AAAAAAAABsM/KhY_s1bC-FM/s1600/1933+POU+DU+CIEL.jpg

Mignet HM 14 Pou du Ciel (picture source). The initial type flew with a motorcycle engine of 17 HP. OK, the wings are not of equal size, but nearly. Close enough to count.

But the type had issues due to the small distance between both wings. Please read this answer for details.

And now please do me (and, hopefully, yourself) a favor and see the "lift destroying" elevator with different eyes. This lower lift (or even downforce) is only the consequence of static longitudinal stability, and both can easily be eliminated by shifting the center of gravity back to the neutral point of a configuration. But if you desire to have some natural stability, you will need to accept "lift destruction" regardless of the configuration. To paraphrase a popular song: Birds do it, bees do it …

… even educated flying wings do it, I might continue. Canards, tandem wings, they all will use the rear part of their lifting surfaces less if they want to achieve static stability. And the most efficient way of achieving it is by using the smallest surface of two for this lower lift. This has the additional benefit that the "rear wing" will be entirely within the downwash field of the forward wing, so it will see less angle of attack variation than the wing and be in a uniform flow field.

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There are many good reasons for a tandem wing, and a few bad ones.

A few responses mentioned influence factors from the forwards wing, that is not bad if it is designed in. With any design, including flying wings, the "tail" is built into the rear (or rear portion) of the wing. So a flying wing or canard will have more wing area than a 'conventional' plane of the same performance. For efficiency, you want long slender wings. If you made two long slender wings in tandem, you wind up making the chord (wing width) shorter, which put you into a lower Reynolds number which means higher drag, and your airfoil thickness is less, which means your spar height is less, which could mean a heavier wing.

On the bright side, your fuselage becomes lighter (weight being distributed more evenly) and you can build in stall resistance. For some aircraft, like the Ligeti Stratos, you can join the wings to add strength (like a biplane). Shorter wings means a higher roll rate, smaller wings could means better control in turbulance. Tandem wings also offer control coupling to make things like translation without rotation possible.

Most of all, I just think it goods good.

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Another point that was not brought up yet is the rotational center of the airframe - specifically pitch and yaw would require much more effort to rotate. When you have single set of wings in the center of gravity, rotating the airframe takes less effort compared to when you have 2 sets of wings and center of gravity in the middle.

enter image description here

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