How a wing makes lift
Turn the air down, get pushed up. Angle of attack, pressure and stall, without the equal transit time myth.
The problem,
and the picture.
The brief
The most popular explanation of lift, equal transit time, is wrong. NASA says so. The film had to give the right one in under a minute.
The approach
A wing cross-section in a field of moving air particles. The flow turns down behind it and a lift arrow grows. Pressure zones appear above and below, then the wing tilts further until the flow separates and it stalls.
- FieldAviation
- Runtime0:58
- Made forStudio sample
- SourceNASA Glenn Research Center, Beginner's Guide to Aeronautics
The narration.
Planes are heavy. So how does a wing hold one up? As the wing moves, it meets the air at a slight angle, called the angle of attack. Both surfaces of the wing turn the passing air downward. Push air down, and the air pushes the wing up. That's Newton's third law, and that's lift. The same turning shows up as pressure. Air speeds up over the top, so the pressure there drops. Below the wing, it's higher. Low above, high below: the wing is pushed up. Tilt the wing up a little, and it turns more air, so lift grows. Tilt too far, and the airflow separates. The wing stalls. And the idea that air over the top must catch up with the air underneath? It's a myth. Turn the air down, get pushed up. That's how a wing makes lift.