What does it mean for a fighter jet to stall?

"Stalling" is the instability of the aircraft caused by the increase of the angle of attack of the aircraft wing. When the angle of attack exceeds the stall angle of attack, the aircraft will produce uncontrolled dive and bump motion, and the engine will fail. Vibration may cause the pilot to feel abnormal control, resulting in a flight accident.

From the perspective of aircraft control principles, the pilot's control does not directly change the trajectory of the aircraft, but changes the attitude of the aircraft. As long as the aircraft has sufficient flight speed to produce a certain rudder effect, the aircraft will The attitude of the aircraft will change, and the change of the aircraft's attitude will change the angle of attack, but the pilot's control will not increase the angle of attack without limit, because as the angle of attack increases, the centripetal force that causes the aircraft to move upward in a circular motion will also Increase, this centripetal force changes the trajectory of the aircraft. The difference between the aircraft attitude angle increase and the aircraft trajectory angle increase is the angle of attack increment. Within a certain flight speed range, this angle of attack increment is not enough to make the plane fly. The angle of attack of the aircraft exceeds the stall angle of attack, so under normal circumstances, it is relatively safe for the pilot to control the aircraft by pulling the stick. And if the flight speed is reduced to a certain value, or the pilot's control amount exceeds a certain value, when the increase in trajectory angle can no longer follow the increase in attitude angle, it will cause a sharp increase in the angle of attack, causing the angle of attack to exceed the stall angle of attack. situation.

——The crash of the B-2 in Guam in 2008 was caused by stalling

The aircraft sometimes automatically enters a stall. Due to insufficient power of the aircraft, the speed decreases or disappears, directly The resulting lack of lift makes it difficult for the aircraft to maintain its original flight state, resulting in a downward trajectory, that is, entering a dive state. At this time, if the aircraft's attitude cannot follow the aircraft's trajectory and dive down, it will cause a sharp increase in the angle of attack and enter a dive state. stall condition.

——The Boeing passenger plane accident on April 29 was a typical stall accident caused by insufficient lift

Stalls are common in the following situations:

1. Low-speed maneuvers

When flying at low speed, the aircraft's maneuverability is weak and it is easy for the attitude change to cause a sharp increase in the angle of attack. At this time, the pilot is prone to focus on changes in other environments and aircraft status, which will reduce his alertness, resulting in unconscious erroneous controls and causing a stall.

——In 1994, this B-52 stalled and crashed at Fairchild Air Force Base. The reason was that the pilot performed a sharp turn at low altitude and low speed, and no one in the crew survived.

2. Dangerous weather

Dangerous weather conditions, such as crosswinds, strong convection, wind shear, etc., will cause significant changes in the aerodynamic force of the aircraft, which will have a negative impact on the pilot's ability. Driving skills place special demands. Inability to cope with weather conditions and major errors in control are an important cause of stalling accidents.

3. Weak power flight

Insufficient power is an important reason for aircraft stalling. On the one hand, due to insufficient power, it is difficult to increase the speed, and the maneuverability of the aircraft is weak, which is prone to operational errors. On the other hand, when flying with weak power, it is easy to cause a sharp attenuation of speed and a sharp loss of energy, and enter a low-speed flight state without the pilot noticing.

4. Take-off and landing phase

During the take-off and landing phase, the aircraft is flying at a low speed and is prone to stalling. On the other hand, the landing gear is lowered, which changes the structure of the aircraft. The shape and aerodynamic shape of the aircraft reduce the maneuverability and stability of the aircraft. Especially during the turning phase, departure and landing phases, the pilot's control is frequent and complex, which is prone to sudden changes in status, leading to stalling.

——The Su-33 pulled the lever too hard during landing and almost stalled