How do helicopters fly?

Each rotor blade has an aerofoil shape, so as it spins it creates lift like an aeroplane wing. The pilot uses the collective control to change the angle of all blades at once, making the helicopter climb or descend. The cyclic control tilts the rotor disc, directing some lift forward, backward or sideways so the helicopter moves that way. Because the spinning main rotor would make the body turn the opposite way, most helicopters use a tail rotor to counter this torque. Some designs, like the Chinook, instead use two main rotors spinning in opposite directions.