Quote:
Originally Posted by Stewart Way
Please explain how a plane stays in level flight with zero lift. Would think it would need lift equal to its weight.
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There are four forces that keep the airplane; thrust, weight, lift and drag.
Thrust, like any other object, keeps and maintains the forward motion.
Weight maintains the center of gravity or the center of mass so the airplane can fly as close to level as its design, minimizing the aircraft controls input. Its correlation is to thrust for its forward motion.
Drag, as any other object in motion is always there and the airplane, like any other vehicle, is designed to reduce the drag by reducing its footprint or coefficient of drag.
Lift is dependent of the airflow around the object as it moves forward due to thrust. There are other variables such as the shape of the object and weight. In the case of an airplane, the air moves around the wings give and maintain the airplane lift.
Zero lift is a term used in flight dynamics science in which during level flight there is an equilibrium of the yaw, pitch and roll axis during flight which is also known as leveled wings or Zero bank angle. In this configuration, the forces are balanced for optimum aircraft performance and operation.