Flight
Lift, Drag & Aerofoils
14 min · 2 worked examplesFree
How a wing makes lift, why it stops working past a certain angle, and the two kinds of drag that fight each other.
After this lesson you can
- Name the four forces and what balances what
- Explain what a stall actually is
- Say why induced and parasite drag pull in opposite directions
Where lift comes from
A wing turns air downwards. By Newton's third law, the air pushes the wing up. That is the honest description, and it is sufficient.
The pressure account is the same thing seen differently: the flow over the upper surface is faster and its pressure lower, and integrating that pressure difference over the wing gives the same force. Both descriptions are correct and they are not competing explanations.
The lift equation is L = ½ρv²SCL, air density, velocity squared, wing area, and a lift coefficient that depends on the shape and the angle of attack.
The v² is the term that dominates. Doubling airspeed quadruples lift, which is why takeoff speed matters so much and why a heavily loaded aircraft needs a longer run rather than a bigger engine.
In the full lesson
- Where lift comes from
- Angle of attack and the stall
- Two kinds of drag
Free with an account. Read it, work the examples, answer the questions, then build it in the simulator.