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V tails have not been common but more and more designs are using them, particularly high performance military aircraft. There are aerodynamic and structural advantages to a V tail but the calculations are more difficult as well as the added complexity of mixing the rudder and elevator inputs.
Its seems that the tail we view as normal, conventional and reliable is used because the penalties are small and it is easier to design and build one. Besides, the customer is used to it and therefore prefers it. Sized correctly a V tail is slightly smaller in total surface area and that means less drag. Interference drag is smaller as a V tail has only one corner between surfaces rather than two, and that means less drag. As the total surface area is divided between two surface areas rather than three their span loading and Reynolds numbers will be better and that means less drag.  There are two distinct advantages to using a V tail on an amphibian. It provides much better clearance from waves. A 'T' tail could be used to achieve that clearance but it adds torsional stress and structural penalties. Any mid engined plane has the propeller relatively close to the tail. With a V tail the turbulent flow passes through the center of the V and the ruddervators are less affected. A V tail really is the best possible configuration for an amphibian. |