How Airplanes Fly
Explain lift, stalls, and drag correctly, spot the myths almost everyone repeats, and read a wing like an engineer.
This course is for members
$9 unlocks every course in the library, this one included, plus a credit to build a topic of your own and at least 10 new courses every month.
What you will learn about How Airplanes Fly
The 7-day sprint
- The Four Forces and Where They Point. An airplane is always in a tug of war between lift, weight, thrust, and drag, and three of those four are defined by the direction the airplane is moving through the air, not by the ground.
- Air Is Stuff, and Only Moving Air Makes Lift. Lift is generated by the difference in velocity between the object and the air, so there must be a fluid present and there must be relative motion between the airplane and that fluid.
- Lift Is Turning the Flow. All that is necessary to create lift is to turn a flow of air, so any body that produces a net turning of the flow makes lift, curved wing or not.
- The Lift Equation. Lift equals the lift coefficient times dynamic pressure times wing area,
L = Cl * (rho * V^2 / 2) * A, and the speed term is squared. - Angle of Attack and the Stall. Angle of attack is the angle between the relative wind and the chord line of the airfoil, and the wing stalls when that angle exceeds the critical angle of attack, at any speed and any attitude.
- Drag, Especially the Kind That Lift Creates. Drag comes in three flavors, friction, pressure, and induced, and induced drag is the unavoidable bill that a finite wing pays for producing lift.
- Killing the Myths, and the Grown-Up Explanation. The equal transit time story is measurably wrong, Bernoulli and Newton are not rival explanations, and the real engineering answer is circulation fixed by the Kutta condition.
The 80/20: the 7 concepts that matter most
- Lift is the reaction to turning a flow
- The four forces point relative to the airflow, not the ground
- Lift scales with the square of speed
- Angle of attack, and a critical angle that never changes
- Induced drag is the price of lift
- Bernoulli and Newton are the same story, told twice
- Circulation and the Kutta condition
The core idea, explained like you are 5
A wing flies by turning moving air downward, and the air pushes back on the wing just as hard, which is lift.
Then the quiz and the ladder
10 questions that correct you when you are wrong, and beginner, intermediate, advanced levels, each with a practical exercise.
Created Sep 13, 2026. No mistakes have been reported by learners.
Written from these sources
- What is Lift? | Glenn Research Center | NASA, www1.grc.nasa.gov. definition and direction of lift, days 1 and 3.
- Lift | Glenn Research Center | NASA, www1.grc.nasa.gov. day 2, relative motion and vacuum requirement.
- Factors That Affect Lift | Glenn Research Center | NASA, www1.grc.nasa.gov. day 3 and top Pareto concept, turning the flow.
- Lift Equation | Glenn Research Center | NASA, www1.grc.nasa.gov. day 4 lift equation and lift coefficient.
- Guide to Aerodynamics | Glenn Research Center | NASA, www1.grc.nasa.gov. framing of aerodynamics across the course.
- www.grc.nasa.gov, grc.nasa.gov. day 7 equal transit time myth and its failure.
- Bernoulli and Newton, grc.nasa.gov. day 7, Bernoulli versus Newton and Venturi theory.
- Computer drawing of an airliner. Induced drag coefficient equals lift, grc.nasa.gov. day 6 induced drag, vortices, aspect ratio.
- On the Origins and Relevance of the Equal Transit Time Fallacy to Explain Lift, arxiv.org. history of the equal transit fallacy and circulation fix.
- Education Sciences (Jul 2023), doaj.org. expert stage claim that lift is well understood.
- Pilot’s Handbook of Aeronautical Knowledge | Federal Aviation Administration, faa.gov. FAA handbook scope, forces of flight framing.
- Chapter 5: Aerodynamics of Flight, faa.gov. day 1 forces, Bernoulli and Newton taught together.
- The Four Forces | How Things Fly, howthingsfly.si.edu. day 1 four force definitions and equilibrium.
- Forces of Flight | How Things Fly, howthingsfly.si.edu. day 1 design tradeoffs among the four forces.
- Welcome to How Things Fly, howthingsfly.si.edu. vertical climb example in day 1 and Pareto.
- The Four Forces of Flight: Explainer Demo | National Air and Space Museum, airandspace.si.edu. day 2, air has mass and sea level pressure.
- Stall Performance - CFI Notebook, cfinotebook.net. day 5 angle of attack, critical AOA, boundary layer.
- Not All Airfoils Stall The Same, Part 1 | Aviation Week, aviationweek.com. day 5 progressive separation, high-lift devices, camber.
- Kutta%E2%80%93Joukowski theorem, en.wikipedia.org. day 7 and expert stage, circulation theorem.
- Kutta condition, en.wikipedia.org. day 7 Kutta condition and starting vortex.
- The Kutta-Joukowsky condition, galileo.phys.virginia.edu. expert stage, thin airfoil theory and theory limits.
- Lift Balance - Operation | Glenn Research Center | NASA, www1.grc.nasa.gov. Wright brothers wind tunnel and lift balance detail.