A tail configuration where the horizontal stabilizer is mounted on the top of the vertical stabilizer.
A T-tail is a tail configuration where the horizontal-stabilizer and elevator surfaces are mounted on top of the vertical-stabilizer, causing the aircraft's tail surfaces to resemble the letter T when viewed from directly in front of or behind the aircraft (hence the name "T-tail").
T-tails are usually only used on aircraft with tail-mounted engines (where the engines take up the space where the horizontal stabilizers would normally go), such as the McDonnell Douglas dc-9-family and boeing-727, as the configuration has several disadvantages compared to a conventional tail:
- The vertical stabilizer has to be stronger (and, thus, heavier) than with a conventional tail, as it has to carry the weight and aerodynamic loads of the horizontal tail.
- Elevator and horizontal stabilizer maintenance is more difficult than with a conventional tail, as these surfaces are much higher up and harder for the mechanics to reach, inspect, and repair.
- T-tailed aircraft are susceptible to an extremely dangerous variant of a stall, known as a "deep stall", where the disturbed airflow coming off the wings blankets the horizontal tail, reducing the aircraft's pitch control authority to near zero and making recovery from the stall very difficult or impossible.