Helicopters have rotor blades above them that are aerofoils. When they turn rapidly, they create lift. The blades are tilted slightly, so that they also provide thrust. The helicopter’s tail rotor blades stop the helicopter from spinning and enable it to turn. With this combination of rotors, a helicopter can move in any direction or simply hover. Without long wings, helicopters can manoeuvre in tight places, such as alongside cliff faces, so they are particularly useful for rescue and emergency work.
The science of a helicopter is exactly the same as the science of an airplane: it works by generating lift—an upward-pushing force that overcomes its weight and sweeps it into the air. Planes make lift with airfoils (wings that have a curved cross-section). As they shoot forwards, their wings change the pressure and direction of the oncoming air, forcing it down behind them and powering them up into the sky: a plane’s engines speed it forward, while its wings fling it up. The big problem with a plane is that lots of air has to race across its wings to generate enough lift; that means it needs large wings, it has to fly fast, and it needs a long runway for takeoff and landing.
Helicopters also make air move over airfoils to generate lift, but instead of having their airfoils in a single fixed wing, they have them built into their rotor blades, which spin around at high speed (roughly 500 RPM, revolutions per minute). The rotors are like thin wings, “running” on the spot, generating a massive downdraft of air that blows the helicopter upward. With skillful piloting, a helicopter can take off or land vertically, hover or spin on the spot, or drift gently in any direction—and you can’t do any of that in a conventional plane.
