Why is there a triangular gap between the trailing edge of the fighter wing and the leading edge of the tail?

If the horizontal tail is closer to the main wing, the efficiency of the horizontal tail will be further reduced due to the influence of the airflow of the main wing, and finally the pitching moment required by the aircraft will not be achieved. Although the inference vector can make up part of it, it can't completely replace the horizontal tail.

Just like the previous high-hanging horizontal tail, the structure of stabilizer and rudder surface is adopted, because the horizontal tail is basically unaffected by the main wing, and the efficiency is high, and the rudder surface does not need to be made very large.

Modern aircraft mostly use low horizontal tail, so that the horizontal tail and the main wing are almost on the same plane. Due to the influence of the main wing airflow, the efficiency of the horizontal tail is greatly reduced, and the rudder area needs to be larger, so this kind of aircraft adopts full-motion horizontal tail.

On the premise that the stealth of the aircraft can meet the needs, the aircraft should of course pay more attention to its maneuverability. This design is mainly based on aerodynamic characteristics.