Flight
Stability & Control
14 min · 2 worked examplesFree
The difference between an aircraft that returns to level by itself and one that needs a computer to stay pointing forwards.
After this lesson you can
- Name the three axes and what controls each
- Say what makes an aircraft statically stable
- Explain why a quadrotor is unstable on purpose
Three axes
An aircraft rotates about three axes, and each has its own control surface.
Pitch is nose up and down, controlled by the elevator. Roll is wings up and down, controlled by ailerons. Yaw is nose left and right, controlled by the rudder.
They are not independent in practice. Rolling into a turn produces adverse yaw, because the wing generating more lift also generates more induced drag and drags backwards, which is why a coordinated turn needs rudder as well as aileron.
A multirotor has the same three axes but no surfaces at all. It controls every one by varying the relative thrust of its motors, which is why it cannot fly for an instant without a working control loop.
In the full lesson
- Three axes
- Static stability
- Deliberate instability
Free with an account. Read it, work the examples, answer the questions, then build it in the simulator.