A twin tail is an aircraft with a set of two stabilizers mounted vertically on the tail assembly. Aircraft with this configuration are more stable and easier to control. The twin tail design was especially popular during the Second World War and continues to be used in the production of a number of aircraft today, including both small and large planes. This design is easy to identify at a glance, as the configuration tends to stand out.
On a twin tail aircraft, there is a large horizontal stabilizer, with smaller vertical stabilizers mounted at either end in a distinctive H shape. These stabilizers act as rudders, keeping the aircraft level and allowing the pilot to control the dynamics of the plane while it is in flight. Unlike single tail aircraft, they can be smaller, as the plane is not relying on one rudder for stability. Having two will usually increase rudder surface area over that of a single tail, providing a higher degree of control.
In a variation on the twin tail design, a plane can have two fuselages connected to a single horizontal stabilizer, with twin tails at the ends to keep the plane stable. This design is commonly seen in military aircraft and is referred to as a double tail or twin boom tail. Engineers working on designs for new aircraft can consider the applications the plane is being designed for and select the best body shape and tail assembly for the situation.
One advantage to the twin tail is the ability to control the plane even if one tail becomes compromised. For military planes, this is important, as enemy aircraft, as well as anti-aircraft guns may aim for the tail with the goal of destabilizing the plane so the pilot can no longer control it, forcing it to the ground. The small tails are harder targets to hit accurately, and if a hit is landed on one of the rudders, the other will still operate. The plane will be harder to control, but it will not be completely destabilized and the pilot has a chance of reaching safety.
The lower profile of this configuration can also be useful when arranging planes in hangars, as they do not need as much clearance. Additionally, in the case of military planes, tail gunners have more visibility and range when they do not need to work around a very prominent single tail. These advantages can all be design considerations when developing new planes.