Aerodynamics · Interactive Student Tutorial

Aircraft Lift, Airflow & Stall

Change airfoil camber, airspeed, and angle of attack. Watch the airfoil shape and airflow respond, calculate lift, compare lift with aircraft weight, and see why increasing angle of attack eventually stops helping when the wing stalls.

L = ½ ρ V² S CL

The central idea

Lift depends on the air, the aircraft's speed through it, wing area, and the lift coefficient. Camber and angle of attack strongly influence CL; speed influences the dynamic pressure term ½ρV².

01 · Lift basics

Three controls, three different aerodynamic effects

Camber

Shape of the mean line

Camber is the curvature of an airfoil. A positively cambered airfoil can produce positive lift even at zero geometric angle of attack because its zero-lift angle is shifted negative.

Airspeed V

Controls dynamic pressure

Dynamic pressure is q = ½ρV². If every other quantity remains unchanged, doubling speed produces four times the dynamic pressure and therefore four times the lift.

Angle of attack α

Changes lift coefficient

Angle of attack is the angle between the wing chord line and the relative wind. Before stall, increasing α usually increases CL approximately linearly.

L = q S CL,    q = ½ρV²,    CL ≈ a(α − α₀) before stall

Why airflow changes direction

For positive lift, the wing turns the surrounding airflow downward. The air exerts an equal and opposite aerodynamic force on the wing. Pressure differences around the airfoil and the momentum change in the airflow are two consistent ways of describing the same fluid-dynamic interaction.

What this tutorial is modeling

This page uses an educational, quasi-steady aerodynamic model. The attached-flow region follows a typical lift-curve slope, camber shifts the zero-lift angle, and a simple post-stall decay represents flow separation. It is not a CFD solver and should not be used for aircraft design, certification, or flight planning.

02 · Interactive laboratory

Change the wing and flight condition

The three large controls are the ones to explore first. Advanced values are supplied so the page can turn the dimensionless lift coefficient into an actual force.

2.0% chord
0% symmetric6% strongly cambered
40 m/s
0100 m/s
5.0°
−12°24°
Advanced aircraft and atmosphere inputs
kg/m³
m²
kg
m

Airfoil and relative airflow

Attached flow
α = 5° Lift Drag Relative airflow → Streamlines are schematic, not CFD.

What the forces mean for the aircraft

Force balance
Lift Weight Relative wind This compares vertical force magnitudes only; actual flight path also depends on thrust, drag, pitch dynamics, and pilot/control inputs.
Lift coefficient CL
—
Dynamic pressure q
—
Lift
—
Lift / weight
—
Zero-lift angle α₀
—
Estimated + stall angle
—
Drag estimate
—
Reynolds number
—
03 · Stall

Why more angle of attack eventually gives less lift

1

Attached-flow region

At modest angle of attack, the boundary layer largely remains attached to the upper surface. Lift coefficient increases approximately linearly with α.

2

Adverse pressure gradient strengthens

As the flow moves toward the trailing edge, it must recover toward ambient pressure. At high α, this pressure recovery becomes difficult for the slower boundary-layer air.

3

Flow separates

The boundary layer can reverse locally and separate from the surface. A broad turbulent wake forms over part of the upper surface.

4

Lift falls and drag rises

Once significantly stalled, increasing α no longer produces the pre-stall lift increase. The lift coefficient drops from its peak while drag grows strongly.

Lift curve for the current camber

The curve is generated from the same simplified educational model used by the simulator. The current angle of attack is marked on the curve.

A stall is primarily an angle-of-attack phenomenon, not simply a low-speed phenomenon. Low speed matters because the aircraft may need a larger lift coefficient, and therefore a larger angle of attack, to support its weight. The wing stalls when its critical angle of attack is exceeded.
04 · Guided experiments

Use the simulator like a small wind tunnel

Choose a preset, observe the visual and force outputs, then change only one control at a time.

Experiment A · Camber

Compare presets 1 and 2. The geometric angle of attack stays at 0°, but positive camber moves the zero-lift angle negative, so the cambered wing develops positive lift.

Experiment B · Speed squared

Compare presets 3 and 4. The aerodynamic coefficients stay approximately the same because α and camber are unchanged, but increasing speed from 25 to 50 m/s multiplies dynamic pressure and aerodynamic forces by about four.

Experiment C · Stall

Compare presets 5 and 6. The larger angle does not guarantee more lift. After the critical angle, the separated-flow model reduces CL and raises drag.

05 · Tutorial data

Useful values and relationships

QuantityTypical educational value or rangeWhy it matters
Sea-level standard air densityabout 1.225 kg/m³Lift is directly proportional to density.
Dynamic pressureq = ½ρV²Contains the speed-squared effect. This is why speed changes aerodynamic force so strongly.
Airfoil camber0–6% of chord is a useful classroom exploration rangePositive camber typically shifts the zero-lift angle to a negative value and changes maximum lift behavior.
Pre-stall lift-curve slopeoften roughly 0.08–0.11 per degree for many subsonic wing/airfoil examplesExplains the near-linear increase of CL with α before nonlinear effects dominate.
Critical angle of attackoften roughly 12–18° for conventional subsonic airfoils, but highly configuration-dependentBeyond this angle, significant separation can cause stall.
Reynolds numberRe = ρVc/μChanges boundary-layer behavior, transition, drag, and stall characteristics. Real stall cannot be predicted from α alone.
In the simulator, a 2% cambered wing has a negative zero-lift angle. Set α = 0° and compare it with a symmetric wing. This demonstrates why camber can create lift without a positive geometric angle of attack.
Real wings are three-dimensional. Finite span creates wingtip vortices and induced drag, while flaps, surface roughness, Reynolds number, Mach number, sweep, icing, and unsteady motion can all change the lift curve and stall angle.
06 · Concept checks

Test the physics, not just the calculator

1. If speed doubles while CL, density, and wing area remain fixed, what happens to lift?

Lift increases by a factor of four because lift depends on V².

2. Can a cambered airfoil produce positive lift at 0° geometric angle of attack?

Yes. Positive camber can shift the zero-lift angle to a negative angle, leaving a positive effective angle relative to the zero-lift condition.

3. Does an aircraft stall because its airspeed reaches one universal number?

No. Aerodynamic stall occurs when the wing exceeds its critical angle of attack. A particular stall speed applies only for a particular weight, configuration, load factor, density condition, and set of assumptions.

4. Why can lift decrease when angle of attack is increased beyond the stall angle?

The upper-surface flow separates strongly. The wing no longer maintains the attached pressure distribution responsible for the pre-stall lift increase, so CL falls while drag rises.