A little bit of theory: How do Quadcopters fly?

How do Quadcopters fly?


Quadcopeters as the name suggests use four motors to fly. Two motors rotates in clockwise direction and another two in counterclockwise direction. In this way their are balancing quadcopters rotation. When four clockwise motors would be used on the copter, it will start rotating always in clockwise direction and if only four counterclockwise motors copter would be rotating in counterclockwise direction. Having two pairs of contrary motors cause Quadcopters to stay in place. Peacefully hovering above ground. When speed on all motors equally increases or decreases drone will vertically take-off from the ground or

Good to know: lift, drag and thrust.



Quadcopter or any other copter, airplane or object can be rotated around three axis, they are called roll, pitch and yaw.

  • Rotation around the front-to-back axis is called roll.
  • Rotation around the side-to-side axis is called pitch.
  • Rotation around the vertical axis is called yaw.

Airplanes use ailerons, rudder and elevator to rotate around one or another axis. However copters doesn’t have them instead use four motors with propellers. Airplanes are more intuitive to understand but quadcopters are not as complex as they look.


Roll, Pitch & Yaw

Always to rotate drone through one or another axis two motors on one side need to speed up and other two motors on opposite side must be inversely changed.

Roll axis


To lean drone to right both left motors speed need to be increased and speed of both right motors decreased. To lean to left both right motors speed should be increased and left decreased.

Pitch axis



Rotating a drone thought pitch axis requires speed change of back and front motors. To lean forward speed of ‘front’ motors need to be decreased and speed of ‘back’ should be increased. To lean backward speed of ‘front’ need to be increased and ‘back’ should be decreased.

Yaw axis



Yaw axis full move explanation is a little bit more complex then other two axis. I would like to explain the basics here but if you would like to know more, just google it. Also good thing is that all flight controllers have this knowledge injected to their ‘brain’. In the nutshell, to turn drone left or right two diagonally across motors must speed up and second two should slow down.

Setup Raspberry PI (+navio) Raspbian and Flight Control Software (Autopilot)


Setting up Raspberry Pi is very easy and you can find a lot of guides step by step on the internet. By just to make it easy for you I will add quick guide of Raspberry Pi Raspbian OS installation.


Raspbian OS Installation


1) First download: Raspbian Operating System ISO file


2) Download & Install: Win32diskimager Tool which Installs ISO on microSD card)


3) Upload Raspbian ISO to SD Card using win32diskimager


Flight Control Software (Autopilot)


There are two main free flight controllers Ardupilot and PX4. I think they both are good. They have very strong community which as I have noticed works all week to make their software as best as possible. Ardupilot is more mature flight controller which I think also supports more platforms rovers and subs. On the other hand PX4 as I have read is more advance in accordance to multicopters plus has more modern architecture which uses 32bit CPU and supports more peripherals. But also Ardupilot has much much better documentation so for users which are not very tech people it will be much easier to do anything related to drones. As it also contains some documentation about drone build.

My plan is to start with PX4 and see how it will work for me. I will keep you blog posted. If not I will test Ardupilot. I will be also working on their code so I could have some other thoughts later which I will post about. So let’s see how we can install both software on raspbian with navio2.

 Ardupilot Flight Control Software Installation


Whole installation process you can find on emlid.com docs page at:



 PX4 Flight Control Software Installation


PX4 support Navio2 board from I think couple months so there is not much guide how to install it best link I have found is the one below.



Good luck,