How to Fix an FPV Drone That Will Not Arm
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Few things are more frustrating than setting up at the field, flipping the arm switch and hearing nothing. Flight controllers deliberately refuse to arm when something looks unsafe, such as throttle not at zero, the quad tilted too far or no receiver signal. The good news is that Betaflight and similar firmware tell you exactly why. Once you know how to read arming flags, most problems take minutes to fix.
Read the arming flags
Connect the quad to Betaflight Configurator and look at the arming disable flags on the Setup tab, or check the OSD in your goggles, which often shows a warning message. Each flag names a specific reason, such as THROTTLE, ANGLE, RXLOSS, MSP or CLI.
Flags can change as you fix each issue, so recheck after every change. Several flags may be active at once, and the drone will only arm when all of them are cleared.
Throttle and switch setup
The THROTTLE flag means the flight controller sees throttle above the minimum arming value. Check that the throttle stick is fully down and that the Receiver tab shows throttle around 1000 when the stick is at the bottom. Adjust endpoints on your radio if it reads higher.
Also confirm that the arm switch is assigned correctly in the Modes tab and that the switch range actually turns yellow when you flip it. A mismatched AUX channel is one of the most common beginner mistakes.
Angle and calibration
The ANGLE flag appears when the quad is tilted beyond the allowed arming angle. Place the drone on flat ground before arming, and calibrate the accelerometer on a level surface in the Setup tab if the model view appears tilted when the quad is flat.
If you fly acro only, some pilots disable the accelerometer, which removes angle-based arming checks. Understand the trade-offs, since angle and horizon modes need an accelerometer.
Receiver and failsafe
RXLOSS or FAILSAFE flags mean the flight controller is not receiving valid control signal. Check that the receiver is bound, powered and connected to the correct UART, and that the serial RX protocol matches the receiver in the Configuration or Receiver tab.
Move sticks and watch the channel bars in the Receiver tab. If nothing moves, rebind the receiver and check that your radio model is using the correct protocol and packet rate.
USB, CLI and other blockers
Many flight controllers will not arm while connected to Betaflight Configurator over USB, and MSP or CLI flags indicate the configurator is connected or the CLI is open. Disconnect and try again with a battery plugged in.
Other causes include a runaway takeoff prevention trigger, a disabled motor protocol or props-off safety tools. When all else fails, back up your settings with a CLI diff and compare them with a known working configuration.
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