T-Tail versus Conventional-Tail
There are a lot of different ways the tail of the aircraft can be designed. There are some with two vertical stabilizers (Sukhoi-27, F/A-18, Antonov-225) and three vertical stabilizers (Lockheed Constellation), V-Tail, Y-Tail, etc. Out of the many, two are compared, the T-Tail and the Conventional-Tail, referred for convenience as C-Tail. Both are depicted in the diagram below.
The T-Tail had the horizontal stabilizers on top of the vertical stabilizer whereas the C-Tail is mounted on the AFT of the fuselage at the bottom of the vertical stabilizers.
The T-Tail usually had a clean airflow while the C-Tail usually lies in the wake of the wings.
The T-Tail stay further away from the engine exhaust while the C-Tail lies in the wake of the engine exhaust.
The T-Tail has the vertical stabilizer endplated at the bottom by the fuselage and the horizontal stabilizers at the top while the C-Tail is only endplated at the bottom. Therefore, the T-Tail can be made smaller, because, a smaller vertical stabilizer of a T-Tail can efficiently do the job of a relatively larger vertical stabilizer of a C-Tail. This makes the T-Tail lighter. However, the T-Tail needs control mechanism for the horizontal stabilizers built into the vertical stabilizers which makes the T-Tail heavier than the C-Tail. Eventually, a comparison of individual pairs is necessary to determine which one is lighter or heavier.
If the tail is heavy, it will experience effects of increased torque and result in increased flutter.
The T-Tail is more efficient because it has less interference drag and less wave drag. Küchemann body (Tupolev-154) can be used to improve its efficiency.
The T-Tail has horizontal stabilizers mounted on top of the vertical stabilizers which increases the leverage of the horizontal stabilizers, and therefore, they can be built smaller and lighter compared to the horizontal stabilizers in a C-Tail.
The T-Tail can cause a downward pitch moment when in side-slip.
The T-Tail has often been blamed to be the cause for stalling. The T-Tail makes it difficult to recover from a deep stall but it does not cause a deep stall. When the aircraft has a very high Angle of Attack, the wake of the wings envelopes the horizontal stabilizers of a T-Tail causing it to lose control. A similar situation in a C-Tail would ensure that the tail received undisturbed airflow and thus it would have control. It is to be noted that when the aircraft is in a level flight, loss of control in the horizontal stabilizers is a lesser concern than when in a stall like situation. In other words, when the aircraft enters a stall, a stall recovery is attempted. In such a situation, a C-Tail is likely to have more control than a T-Tail. See image at the bottom.
When landing or take-off, the T-Tail experiences more ground effect at the wings but negligible ground effect at the tail. This causes the aircraft to pitch up relatively easily. During landing, this tendency to make the aircraft pitch up makes it easier to land. Many pilots refer to this as the aircraft landing itself.