A helicopter is a type of rotary-wing aircraft in which lift and thrust are supplied by rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward, and laterally. Helicopters are used in a variety of applications, including airlift (transporting people or cargo), medical evacuation, search and rescue, law enforcement, firefighting, agricultural spraying, crop dusting, utility work (such as power line repair), tourism, civil engineering (construction or demolition), forest Fire suppression & fighting , pipeline construction & maintenance) military uses such as troop transport & attack missions.
The main rotor provides lift while the tail rotor counterbalances the torque created by the main rotor so that the helicopter does not spin around uncontrollably. The first successful powered helicopter was built by French engineer Paul Cornu in 1907. His machine hovered for 20 seconds at a height of one foot (30 cm).
In 1918 Igor Sikorsky designed and flew the first successful single-rotor helicopters. The U.S.-built Vought-Sikorsky VS-300 made its maiden flight on September 14th 1939 . It had an enclosed cabin with room for two passengers seated side by side; it was also equipped with skids for landing gear instead of wheels . While single-rotor helicopters continue to be produced today , most have multiple rotors . Multi-rotor designs provide greater stability than single-rotor helicopters but are more complex to build and fly.
One advantage of helicopters over fixed – wing aircraft is their ability to takeoff and land in confined spaces , such as small clearings , parking lots , rivers , lakes or even rooftops . They can also hover in place which is useful when conducting search -and -rescue operations or other tasks that require precise positioning . In addition , because they can fly slowly at low altitudes without stalling , they can be used for photography or other activities that require hovering .
Another advantage is that helicopters can fly vertically upward relative to their body axis ; this permits them to perform maneuvers (known as ” autorotations “) that would result in a stall if attempted by a fixed – wing aircraft . In an autorotation , air flowing up through the spinning blades provides most of the lift needed to keep the helicopter aloft while descending at a rate slow enough to avoid injuring occupants upon landing . This capability makes helicopters particularly well suited for emergency situations such as medical evacuations from inaccessible locations such as mountainsides or buildings .
While vertical takeoff and landing is one of the defining characteristics of helicopters , some types are able to take off and land horizontally like conventional airplanes do ; these are known as tiltrotors . Tiltrotors typically have large propellers mounted on tilting wings ; when taking off vertically , they rotate their wings so that both propellers face forward providing thrust like an airplane’s engines would during horizontal flight once airborne