The four forces of flight
Meet lift, weight, thrust and drag.
Identify lift, weight, thrust and drag, and recognize why their balance matters.
Lift and weight
Weight acts toward the center of Earth. Lift is the component of aerodynamic force perpendicular to the relative airflow. Lift does not always point vertically upward: a banking airplane tilts its lift vector.
Thrust and drag
Thrust comes from the propulsion system. Drag resists motion through the air. These forces are balanced in straight, level flight at constant speed.
Put it together
An airplane that accelerates has an unbalanced net force. A climb is not simply a matter of lift becoming greater than weight; thrust, flight path and force directions all matter.
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Sample lesson · Editorial review pending. Educational introduction, not flight instruction.
Further reading: FAA handbook