How a drone flies
Four propellers, four motors
A propeller pushes air down; the air pushes the propeller up. That push is thrust. A quadcopter has four, and it controls everything by changing their speeds:
| You want | What the motors do |
|---|---|
| climb / descend | all four faster / slower |
| tilt forward (and so fly forward) | rear motors faster, front motors slower |
| tilt sideways | one side faster |
| turn on the spot (yaw) | the two clockwise propellers faster than the two anticlockwise ones, or the other way round |
Why two turning each way? Every spinning propeller twists the drone the opposite way (the same reason a helicopter needs a tail rotor). With two clockwise and two anticlockwise, the twists cancel. To turn, the drone deliberately lets one pair twist harder.
A drone cannot fly without a computer
A quadcopter is unstable: left alone, the smallest gust tips it, and it keeps tipping. No human can react fast enough. The flight controller (FC) does it for you:
- a gyroscope measures how fast the drone is rotating, thousands of times per second,
- the FC compares that with what your sticks ask for,
- a PID controller (the same idea as in our mecanum and IK + PID material) calculates how much each motor must change,
- the ESCs (electronic speed controllers) change the motor speeds accordingly.
In Angle mode (for beginners) the FC also uses its accelerometer to keep the drone level when you let go of the sticks. In Acro mode (for racing and freestyle) it only holds the rotation speed you command: let go and the drone stays tilted. You will learn in Angle mode.
The parts
| Part | Job |
|---|---|
| frame | carbon-fibre arms and plates that hold everything |
| motors (4) | brushless motors; their KV says how many rpm per volt, without load |
| propellers (4) | two clockwise, two anticlockwise; size and pitch decide thrust and efficiency |
| ESC (4 in 1) | turns the FC’s commands into the three-phase power the motors need |
| flight controller | the brain, running Betaflight, free open-source firmware |
| receiver | gets your sticks’ commands from the radio |
| radio transmitter | the sticks in your hands |
| LiPo battery | lots of current from little weight; also the most dangerous part |
| camera + video transmitter + goggles (optional) | live video for FPV flying; needs an observer by EU rules |
How much thrust is enough?
The thrust-to-weight ratio (TWR) is the total thrust of all four motors divided by the drone’s weight. Below 2, the drone can barely climb and cannot fight wind. Beginners are comfortable around 3 to 5; racing drones go far beyond. The flight time depends on the battery and how hard you fly. Try it:
What is in this guide
- How a drone flies (this chapter, free)
- The EU rules and safety: before you buy anything
- Choosing the parts
- Building it: soldering and the first power-up
- Betaflight setup
- First flights, batteries and maintenance
