Quadcopter
A four-rotor aircraft enabling simple drone flight control.
A quadcopter, also known as a quadrocopter or quadrotor, is a rotorcraft with four rotors. While experimental quadrotor helicopters and convertiplanes existed for decades, the design remained a novelty until the rise of modern drones. The small size and low inertia of these unmanned aerial vehicles allow for a very simple flight control system, making the small quadrotor practical for the first time.
Each rotor generates lift and torque around its center, plus drag opposing the direction of flight. Typically, two rotors spin clockwise and two spin counterclockwise. Flight is controlled by independently adjusting each rotor’s speed, which changes its lift and torque. Pitch and roll are managed by shifting the net center of thrust, while yaw is controlled by altering the net torque. Unlike conventional helicopters, quadcopters usually lack cyclic pitch control, where blade angles change dynamically as they rotate.
In early aviation, quadrotors (then called helicopters) were seen as a solution to vertical flight problems. Counter-rotation eliminates torque-related control issues and the inefficiency of a tail rotor, which provides no lift. Short blades are also easier to build. Several manned designs appeared in the 1920s and 1930s, and were among the first successful heavier-than-air vertical takeoff and landing vehicles. However, early prototypes performed poorly, and later ones required excessive pilot effort due to weak stability augmentation and limited control.
If all four rotors spin at the same speed—two clockwise, two counterclockwise—the net yaw torque is zero, eliminating the need for a tail rotor. Yaw is produced by unbalancing the aerodynamic torques, such as by offsetting thrust commands between counter-rotating pairs. Quadcopters are subject to normal rotorcraft aerodynamics, including the vortex ring state.
The main mechanical parts are a frame, four rotors (fixed- or variable-pitch), and motors. For best performance and simplest control, the motors and propellers are equally spaced. A quadcopter can also use a coaxial rotor configuration, where each arm has two motors spinning in opposite directions—one facing up, one down—for more power and stability at lower weight.
The quadcopter configuration is relatively easy to program for autonomous flight, enabling experiments with complex swarming behavior based on basic sensing between drones.
- Fastest speed
- 685 km/h
- Longest flight time
- 2 hours, 31 minutes and 30 seconds
- Endurance record holder
- Ferdinand Kickinger of Germany
- Endurance record year
- 2016
- Speed record holders
- Benjamin Biggs and Aidan Kelly
- Speed record location
- Australia
- Speed record date
- 20 May 2026
Lore & Background
Each rotor produces both lift and torque about its center of rotation, as well as drag opposite to the vehicle's direction of flight. Quadcopters generally have two rotors spinning clockwise and two counterclockwise. Flight control is provided by independent variation of the speed and hence lift and torque of each rotor. Pitch and roll are controlled by varying the net centre of thrust, with yaw controlled by varying the net torque. Unlike conventional helicopters, quadcopters do not usually have cyclic pitch control.
In the early days of flight, quadcopters were seen as a possible solution to persistent problems in vertical flight. Torque-induced control issues and efficiency issues originating from the tail rotor can be eliminated by counter-rotation, and the relatively short blades are much easier to construct. A number of manned designs appeared in the 1920s and 1930s. These vehicles were among the first successful heavier-than-air vertical take off and landing vehicles. However, early prototypes suffered from poor performance, and later prototypes required too much pilot workload due to poor stability augmentation and limited control authority.
The first heavier-than-air aerodyne to take off vertically was a four-rotor helicopter designed by Louis Breguet, tested only in tethered flight. Etienne Oehmichen experimented with rotorcraft designs in the 1920s, including the Oehmichen No. 2, which made over a thousand test flights and established the first-ever FAI distance record for helicopters of 360 m in 1924. Dr. George de Bothezat and Ivan Jerome developed the de Bothezat helicopter, which made its first flight in October 1922. The Convertawings Model A Quadrotor, flown many times from 1956, was the first four-rotor helicopter to demonstrate successful forward flight.
Reader's Guide
The quadcopter configuration has become popular for small-scale unmanned aerial vehicles or drones in the first decades of the 2000s. The need for aircraft with greater maneuverability and hovering ability has led to a rise in quadcopter research. The four-rotor design allows quadcopters to be relatively simple in design yet highly reliable and maneuverable. The quadcopter configuration is relatively simple to program for autonomous flight, which has allowed experiments with complex swarming behaviour based on basic sensing of the adjacent drones.
All quadcopters are subject to normal rotorcraft aerodynamics, including the vortex ring state. The main mechanical components are a fuselage or frame, the four rotors (either fixed-pitch or variable-pitch), and motors. For best performance and simplest control algorithms, the motors and propellers are equidistant. A quadcopter can employ a coaxial rotor configuration, where each arm has two motors running in opposite directions, to allow more power and stability at reduced weight.
Notable records include the longest flight time achieved by a battery-powered quadcopter of 2 hours, 31 minutes and 30 seconds set by Ferdinand Kickinger of Germany in 2016, and the fastest speed of 685 km/h by Benjamin Biggs and Aidan Kelly in Australia on 20 May 2026. Alternative power sources like hydrogen fuel cells and hybrid gas-electric generators have been used to dramatically extend endurance. Airbus is developing a battery-powered quadcopter to act as an urban air taxi.
Did You Know?
- The fastest speed achieved by a quadcopter is 685 km/h, set in Australia on 20 May 2026.
- A quadcopter can employ a coaxial rotor configuration with two motors per arm running in opposite directions.
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