ENGINEERING COMMISSION #7973: a working small tunnel with instrument readouts — lift and drag as measured facts; feeds the aircraft-mechanic and pilot cards.
Air Is a Fluid
The first thing the tunnel teaches is that air behaves like water: it flows, it separates, it makes wakes and eddies. A student who has watched smoke break over a wing stops thinking of air as nothing.
Lift Is Not Magic
The wing turns the air downward; the air pushes the wing upward. That is Newton's third law and it is sufficient. The popular "longer path over the top" explanation is wrong, and this panel says so plainly.
Drag, and the Cost of Shape
Two objects of the same frontal area, one blunt and one teardrop, at the same wind speed. The drag differs by a factor of ten. Every fuel bill, every cyclist's crouch, every whale is downstream of this measurement.
The Wright Tunnel
In 1901 the Wrights stopped trusting the published lift tables, built a six-foot tunnel out of a starch box, and tested two hundred wing shapes themselves. The aeroplane was not invented in the air. It was invented in that box.
Stall
Raise the angle of attack and lift rises — until it doesn't. The flow separates, the wake goes wide, and the wing stops flying. Watching stall happen in smoke is the difference between knowing the word and understanding the event.
Scale and the Model
A model is not a small aeroplane; the air does not shrink with it. Reynolds number is how engineers make a small test say something true about a large object — and it is the reason wind-tunnel work is a science and not a hobby.
Smoke breaks over the wing and the vortices become visible — the test section of a working wind tunnel.