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On a number of aircraft such as the:

Antonov 225:

Antonov 225

A10:

A10

F35:

F35

Use twin tail designs. I understand for military aircraft that the benefit is it allows for a small tail cross section. Reducing the chance of it being damaged in combat.

In the case of the A225 and other similarly designed cargo aircraft it means the rear of the aircraft can be more easily designed as a cargo hatch.

Are there any other reasons why a twin tail design is preferable over a single tail design?

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    $\begingroup$ A225 is a special case, as it was first designed to carry the Buran shuttle. There was the same problem as in the Nasa shuttle carrier, the piggybacked shuttle creates turbulent air behind it. So the vertical surfaces are moved away for the center to prevent flutter. But you may imagine the reason for the other design with a central engine. $\endgroup$ – mins Feb 26 '17 at 15:51
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    $\begingroup$ related, but exactly not a dupe. $\endgroup$ – kevin Feb 26 '17 at 21:05
  • $\begingroup$ Possible duplicate of aviation.stackexchange.com/questions/24020/… $\endgroup$ – A. I. Breveleri Feb 27 '17 at 3:04
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This constructive solution can be dictated by a number of reasons:

Aerodynamics - for AN 225, 747 Shuttle Carrier Aircraft, A-10 (control surfaces are more effective outside turbulent air);

Some sort of redundancy - for military airplanes F-35, A-10;

Easier construction - since the surface being smaller aerodynamic loads are smaller the structure can be lighter wight;

Radar cross section - F-35, SR-71;

Stability considerations: the arm for the vertical surfaces is a little longer than the arm of a potentially single surface on the longitudinal axis of the aircraft, so the two vertical surfaces combined can have a less surface area than a potentially single surface.

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Are there any other reasons why a twin tail design is preferable over a single tail design?

Reducing the height to fit into existing hangars with short ceilings. So, it can be a selling point. Instead of one tall fin, the required surface area is split into multiple fins.

enter image description here

The triple tail kept the aircraft's height low enough to fit in existing hangars.— Lockheed Constellation

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    $\begingroup$ Same goes for T-tails: The A400M has a T-tail because this reduced the height of the vertical by 2 meters. $\endgroup$ – Peter Kämpf Feb 27 '17 at 7:13

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