The Machine That Cheats the Need for a Runway: How Helicopters Fly

An airplane must move forward to fly; its fixed wing needs airflow, and airflow needs speed. A helicopter sidesteps that bargain by spinning its wing. The main rotor is, in effect, a set of long, narrow wings rotating around a mast, generating lift whether or not the aircraft is moving over the ground — which is why a helicopter can hover, climb vertically, and fly sideways or backward, reaching places no runway-bound aircraft can. Control is a marvel of mechanical cleverness. The collective pitch control raises or lowers the pitch of all rotor blades together, changing total lift to climb or descend. The cyclic control changes blade pitch at different points around the rotor's circle, tilting the lift and tipping the helicopter in the direction the pilot wants to go. And because spinning the big rotor one way would spin the fuselage the other (torque again), most helicopters add a tail rotor — controlled by the pedals — to counter that twist and steer the nose. Coordinating all three at once, especially in a hover, is famously demanding. The most counterintuitive fact about helicopters is that an engine failure is survivable through a maneuver called autorotation. With the engine gone, the pilot lowers the collective so that air flowing up through the descending rotor keeps it spinning, storing energy like a windmill; near the ground, that stored energy is traded back into lift for a controlled landing. Igor Sikorsky's practical single-rotor design in 1939 launched the type, and today helicopters do the work airplanes cannot — rescues at sea, landings on rooftops, lifts to mountaintops — proving that flight does not always require a runway.