What Is Meant by Flight Equilibrium?

The Forces Acting on the Aircraft in Flight:

These basic forces are:
- Lift, the upward acting force
- Weight (or gravity), the downward acting force
- Thrust, the forward acting force
- Drag, the rearward acting, or retarding, force.

When in flight, there are certain favorable forces and other unfavorable forces acting on the aircraft. It is the primary task of a pilot to control these forces so as to direct the aircraft’s speed and flight path in a safe and efficient manner. To do this the pilot must understand these forces and their effects. Among the aerodynamic forces acting on an aircraft during flight, four are considered to be basic because they act upon the aircraft during all maneuvers.

While in a steady state of flight the attitude, direction and speed of the aircraft will remain constant until one or more of the basic forces changes in magnitude. In steady flight the opposing forces are in equilibrium.