If your plane uses a ESC (electronic speed control) for motor output then you will probably need to calibrate it.
You should remove the propeller from your aircraft before starting ESC calibration
Calibrating your ESC involves teaching your ESC what range of throttle inputs it should respond to. It needs to know what PWM value on the throttle channel corresponds with the commanding the motor to be off, and what PWM value corresponds with full throttle. These values are stored inside the ESC.
You should not try to calibrate your ESC until you have completed both your RC inputscalibration and your servo setup.
Typical ESC Calibration
The most common type of ESC calibration for small electric aircraft is the max-throttle/min-throttle method.
To perform this type of calibration you will need to be able to control power to your motor separately from power to the autopilot. If you don’t have separate power, then you can temporarily power your autopilot from a USB cable for the purposes of this calibration.
The steps for calibration are:
- start with the autopilot powered, but with the motor unpowered or propeller removed
- switch to MANUAL flight mode
- disable the safety switch (if fitted)
- move the throttle stick on your transmitter to maximum
- add power to the motor
At this stage the ESC/motor should beep to indicate that it is in ESC calibration mode. Typically it will be 2 or 3 quick beeps, but the motor won’t turn.
- now lower the throttle stick rapidly to zero
- the ESC should beep to indicate it has accepted the new calibration range
- now slowly raise the throttle and check that the motor responds correctly
Alternative ESC Calibration
If you can’t use the typical ESC calibation method above then you can instead adjust the SERVO3_MIN and SERVO3_MAX values in ArduPilot to match the existing range of your ESC. This assumes you have your throttle on channel 3. If you have assigned the throttle on a different channel then you can adjust the MIN and MAX for that channel.
To use this method slowly raise the SERVO3_MIN value until it is set to a value just below the point that the motor comes on. A value about 20 PWM below the point where the motor starts turning is usually a good choice.
Next move the transmitter stick to full throttle and adjust SERVO3_MAX until maximum RPM is reached. You can use a tachometer, or just use the sound of the motor as a guide.