The Four Aerodynamic Forces Explained! | Theory of Flight 3 ✈️✈️

[@aygunbaylas3376]

Thank you sir!

[@jaesoo1565]

Sir, i have 2 questions From 3:00, if all forces are in equilibrium. Doesn’t the aircraft be either not moving in the sky OR moving in a CONSTANT Velocity in the sky? And on 3:15, if the aircraft is on the ground. It should be in equilibrium cuz there is a reactant NORMAL FORCE acting perpendicular to the weight of the ac if it is on the ground. Correct me if i’m wrong, i’m still a newbie learning aviation.

[@knowledgeexplorer7122]

Wow that’s some great questions, had me thinking for a while! Regarding the first question, it has to be not moving. If it’s moving at some velocity, that implies thrust is greater than drag, hence the forwards motion. However, upon further reflection, I don’t think it’s possible to reach equilibrium by the plane alone. This is because when thrust = drag, the plane has no forward motion. This means no lift would be created by the airfoil, therefore no force to counter balance weight. Hence, I believe the only possible way to achieve equilibrium is to have an external force (ex. Upwards winds) to push the plane upwards and negate the weight of the plane, thus the aircraft will not move and reach equilibrium.

[@knowledgeexplorer7122]

Regarding the second question, you are correct about normal force (that is why the plane is stationary and not falling into the core of the earth) However, I believe these questions are talking about aerodynamic forces, and thus we are only thinking about: lift, weight, thrust, drag.

[@monketeachmonkelearn7054]

​​​​​@@knowledgeexplorer7122 Thanks for clarifying. With what you asked "if the parked airplane is in complete equilibrium" I am thinking this: The horizontal and vertical forces are all equal resulting in the plane parked stationary relitive to the ground. Since these forces are all equal it is necessarily in complete equilibrium. Is there a distinction/term/concept between equilibrium suspended in the air vs on the ground that the test would clarify? Like, would it ask if this parked airplane in airborne equilibrium? I guess there is a difference between static and dynamic equallibrium. The parked airplane wouldnt have a dynamic equallibrium but a static one