What is a Quadcopter?

A quadcopter, also known as quadrocopter, multicopter, multirotor could be described as a Helicopter with four rotors.  Quadcopters are sometimes also called unmanned aerial vehicles (UAV) or Drones. They don’t have tail rotors such as helicopters so they have to compensate for Yaw somehow, otherwise they would continually spin, due to the body counteracting the Yaw forces of spinning rotor blades. Quadcopters accomplish this by spinning 2 propellers clockwise (CW) and 2 propellers counter-clockwise (CCW). Each propeller counterbalancing its opposite spinning  brethren. How does a Quadcopter fly,move , turn/spin (or Yaw)? Great Question. Airplanes deflect air flowing over their control surfaces to move the plane from it’s current path, quadcopters do this by using flight controllers /computers which control the speed of each motor based on the input from the transmitter (TX). To lift the motors simply speed together to lift the aircraft higher. To move side to side or forwards and backwards 2 rotors spin faster than the other 2 and this causes the one side to lift higher and therefore angle the quadcopter to begin moving in the direction requested form the TX. So for moving sideways, or forwards and backwards the flight controller simply picks the correct motors to speed up or slow down. To rotate the quadcopter while hovering in the same space either the CW or CCW motors spin slightly faster than their counterparts which slow down slightly to still overall produce the same amount of lift as before but causing the quad to pivot on its Yaw axis. All these movements are controlled by a very intelligent flight computer which in association with sensors such as gyroscopes, sometimes barometers, and compasses continually monitors the attitude of the quadcopter. Feel free to post your questions...