What is unstart?

Unstart is a phenomenon that can occur in supersonic flight when the airflow over the inlet of the engine breaks down and becomes turbulent. This can cause engine instabilities, power loss, and even flameout. Unstart can happen when the aircraft is flying at certain angles of attack or when the airspeed drops below a certain threshold.

Unstart is a common problem in supersonic flight, especially in high-performance aircraft like fighter jets. It can be caused by a number of factors, including changes in the aircraft's attitude, variations in the air density, and external disturbances like turbulence. Unstart can be prevented or mitigated through careful design of the aircraft's inlet system, as well as by using various control systems and active flow control techniques.

Many modern supersonic aircraft are equipped with sophisticated inlet flow control systems that can prevent or mitigate unstart. These systems use advanced sensors and algorithms to monitor the airflow and control the position and shape of the boundary layer inside the inlet. Some of these systems also use additional air supplies or actuators to adjust the inlet geometry and airflow as needed.

Overall, unstart is a significant challenge in supersonic flight, and researchers and engineers continue to develop new methods and technologies to mitigate this phenomenon and improve the safety and performance of supersonic aircraft.