It is very important to keep the balance of the aircraft when the aircraft is flying. Only keeping the balance on its own flight orbit is the only indicator of whether the aircraft can reach the destination safely. So what is the balance of an airplane?

The balance of an aircraft means that the sum of the forces acting on the aircraft is zero, and the sum of the torques formed by the forces on the center of gravity is zero. When an airplane is in equilibrium, its speed and direction remain the same, and it does not revolve around its center of gravity. On the contrary, when an aircraft is in an unbalanced state, the size and direction of its speed will change and it will rotate around the center of gravity. Whether the aircraft can automatically maintain the balance state, aviation vibration balance instrument is the problem of safety; How to change its original equilibrium state is a manipulative problem. Therefore, the study of aircraft balance is the basis of the analysis of aircraft stability and maneuverability. Aircraft balance includes "force balance" and "torque balance". In flight, the change of the center of gravity velocity of the aircraft directly and whether the forces acting on the aircraft are balanced; The change of the angular velocity of an aircraft about its center of gravity is directly related to whether the torques acting on the aircraft are balanced or not. For the convenience of research, the balance of moment of aircraft is generally studied relative to the three axes of aircraft.

The directional balance and lateral balance of an aircraft are related to each other and tie each other, and the directional balance is destroyed. If not corrected, the lateral balance will be destroyed. On the contrary, if the aircraft vibration balance instrument loses the lateral balance, the directional balance cannot be maintained. The combination of directional and lateral balance of an aircraft is called lateral balance of the aircraft.