What Forces Act on an Aircraft?


The primary forces that act on an aircraft and affect flight are thrust, drag, lift, and weight. The understanding of and ability to control each of these forces is crucial to proper and efficient flight. This blog will define each of them, provide insight into what makes these forces occur, and describe how they affect an aircraft during flight.

Thrust is the forward force produced by the powerplant, propeller, or rotor. In flight, thrust acts to overcome the force of drag - thrust must be greater than drag for an aircraft to begin movement. To maintain a constant airspeed, thrust must be monitored so it is equal to drag. When thrust is greater or less than drag, the aircraft will speed up or slow down respectively. Generally speaking, thrust acts parallel to the longitudinal axis.

Drag is defined as a rearward, retarding force caused by the disruption of airflow over the wing, rotor, fuselage, or other protruding parts of an aircraft. Drag opposes thrust and acts rearward relative to the wind. There are two types of drag: parasite and induced. Parasite drag is the combination of all forces that work to slow an aircraft’s movement. These forces include displacement of air by the aircraft, turbulence in the airstream, or hindrance of air moving over the surface of the fuselage or airfoils of the airplane. The second type of drag is induced drag. Induced drag is based on the fact that no mechanical system can operate with 100% proficiency. When a wing or rotor produces lift, it will inevitably create drag as well. This unavoidable drag is induced drag. Induced drag is always present when lift is being produced.

The third force, lift, is the force that opposes the weight of an aircraft and holds it in the air. It is a mechanical aerodynamic force created by the motion of the airplane through the air. While each part of the aircraft has a role in producing lift, most of it is done by the wings. Lift operates based on Newton’s Third Law of action and reaction. When a moving flow of fluid (liquid or gas) is turned by a solid object, in this case a wing, the flow turns one direction, and lift is generated in the opposite direction. Without fluid and motion, lift is not achievable.

The final force that acts on an aircraft is weight. This is the combined load of the aircraft itself, the crew, fuel, cargo, and baggage. The force of weight is generated by the aircraft’s gravitational attraction to the earth. Unlike lift and drag, which are aerodynamic forces, weight is a field force. Field forces are forces that do not have to be in physical contact with an object to generate an effect on them. For proper flight, the aircraft must overcome the problems presented by its weight while still maintaining control. Weight and lift are closely related. Simply put, lift is the upward force on the wing acting perpendicular to relative wind required to counteract the aircraft weight. During level flight, the forces of lift and weight are equal.

At Buy NSN, owned and operated by ASAP Semiconductor, we can help you find all the rotor blade parts, fuselage parts, and thrust parts for aircraft in the aerospace, civil aviation, and defense industries. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at sales@buynsn.com or call us at 1-919-348-4040.


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