The motor emergency stop is active

What ArduPilot says:

• PreArm: Motors Emergency Stopped

The emergency stop, which cuts every motor at once, is switched on. It is set by a transmitter switch with the function Motor Emergency Stop (RCn_OPTION 31, stop when high) or Arm/Emergency Motor Stop (RCn_OPTION 165, stop when low). While disarmed, the second kind resting in its low position is not reported, because that is where it belongs.

What to do, most likely first

1. The Motor Emergency Stop switch is high.

   FixMove it low, then arm.

2. You tried to arm with the sticks or from the ground station while an Arm/Emergency Motor Stop switch was low.

   FixArm with that switch itself: its high position clears the stop and arms; its middle position clears the stop only.

3. The channel is reversed in the transmitter, or the switch function is on the wrong channel.

   CheckFlip the switch and watch its channel in the Radio Calibration screen; the line “RCn: MotorEStop HIGH” or “LOW” in the messages shows what ArduPilot saw.

   FixCorrect the channel in the transmitter or move the function to the right RCn_OPTION.

The emergency stop works in the air too: it stops the motors and the aircraft falls. Put it on a switch you cannot knock by accident.

Parameters to look at

Where to do it:Setup & Tuning Guide