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enter image description here
Image source: airbus.com

This U-Shaped tail is from a concept aircraft from Airbus, I was wondering if there is an alternative but just as good solution to the U-shaped tail. Using a canard in the front for pitch and winglets on the wingtips?

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  • $\begingroup$ Related: Why is the use of tail-down force so common? $\endgroup$
    – ymb1
    Apr 17 at 19:20
  • $\begingroup$ Could you clarify what ‘good’ means in this context, and whether/why you consider the illustrated design to be bad? $\endgroup$
    – Frog
    Apr 18 at 4:08
  • $\begingroup$ Good as in less surface area of the tail. $\endgroup$ Apr 18 at 7:58
  • $\begingroup$ Off-topic: This appears to me to be another double-decker super heavy along the A380 lines. Hasn't Airbus killed the A380 because there's zero demand for it? Haven't they learned any lessons from that fiasco? $\endgroup$
    – FreeMan
    Apr 20 at 15:37
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In airplane empennage design, there is a thing called Tail Volume Coefficient. Mind you, there are no volumes here, but you are working with $m^3/m^3$. It is calculated as follows:

Horizontal tail volume:

$V_{HT} = \cfrac{ l_{HT} \cdot S_{HT} }{ c_{REF} \cdot S_{REF} }$

Vertical tail volume:

$V_{VT} = \cfrac{ l_{VT} \cdot S_{VT} }{ b_{REF} \cdot S_{REF} }$

here

  • $c_{REF}$ - mean geometric chord (~MAC)
  • $b_{REF}$ - wingspan
  • $S_{REF}$ - reference wing area
  • $l_{HT}$ - horizontal tail arm
  • $l_{VT}$ - vertical tail arm
  • $S_{HT}$ - horizontal tail area
  • $S_{VT}$ - vertical tail area

Now, with that in mind, you can have a perfectly reasonable cruciform solution, U-tail, H-tail, or triple-tail solution, or whichever.

However, freely choosing empennage configuration is not the only condition in design. Engineers likely have other requirements. These two vertical stabilizers (VS) look relatively slender. Perhaps a single VS would be too slender and cause structural issues, perhaps flight dynamics department required better yaw or sideslip control, in which two VSs would maybe be proved better. I think Russians designed An-225 with an H-tail to carry extreme payloads (like Buran), whereas Americans didn't modify 747's empennage for Space Shuttle carrying. There are a number of considerations here. One of which, mind you, is also aesthetics, especially for a passenger airliner.

So, is there a better solution than the U-shaped tailplane for this Airbus concept? It depends. There is no single universally best solution in these things.


Equations from S. Gudmundsson: General Aviation Aircraft Design

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    $\begingroup$ Americans did modify the empennage of Shuttle Carrier aircraft—it has additional vertical stabilizers attached to the ends of the horizontal stabilizer. The dorsal load reduces effectiveness of the central vertical stabilizer, so they had to add a bit of H configuration too. $\endgroup$
    – Jan Hudec
    Apr 19 at 7:05
  • $\begingroup$ @JanHudec You are right! I completely missed that! $\endgroup$
    – Mat
    Apr 19 at 12:10

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