An FPV drone that won't arm is almost always being blocked by Betaflight's safety checks. The flight controller names the reason as an "arming disable flag": the most common are RXLOSS (no radio link), THROTTLE (throttle not at zero), ANGLE (the quad isn't level) and ARMSWITCH (the arm switch was on at power-up). Find the flag, fix that one thing, and the quad arms.
Find out why it won't arm
Betaflight tells you exactly what's blocking it. Look in one of three places:
- Goggles OSD. Most setups show the active flag as a warning on screen when you flip the arm switch.
- Betaflight Configurator, Setup tab. The arming disable flags are listed live.
-
CLI. Type
statusand read the "Arming disable flags" line.
The usual flags and fixes
- RXLOSS / BADRX / FAILSAFE: the flight controller isn't getting a valid signal. Check the receiver is bound to your radio, the radio is on the right model, and the receiver protocol and UART match in the Ports and Receiver tabs.
- THROTTLE: throttle isn't at its lowest. Lower it fully, and check the Receiver tab shows throttle near 1000 at the bottom. Adjust endpoints in the radio if it doesn't.
- ARMSWITCH: the arm switch was on when the quad powered up. Flip it off, then on again.
- ANGLE: the quad is tilted past its small-angle limit (25 degrees by default). Put it on level ground. If it's level and still flagged, calibrate the accelerometer in the Setup tab.
- CALIB / NO_ACC_CAL: sensors are calibrating or the accelerometer was never calibrated. Wait a few seconds, or calibrate it on a level surface.
- CLI / MSP: the Configurator or CLI is connected. Disconnect USB to arm normally.
- RPMFILTER: the RPM filter is on, but the ESCs aren't sending bidirectional DShot telemetry. Enable bidirectional DShot or turn the filter off.
- REBOOT_REQD: you changed a setting that needs a reboot. Power cycle.
- RUNAWAY / CRASH: a protection tripped. Disarm, check props and motor direction, and power cycle.
It arms but won't take off
- Props on wrong. Check rotation direction against the motor layout in the Motors tab (props in or props out).
- Motor order or direction wrong. Test each motor with props off in the Motors tab.
- Throttle too low. In Acro mode the quad needs throttle to lift off; there's no altitude hold.
- Weak battery. A sagging pack can trip a low-voltage warning or not have enough punch.
Not connecting to Betaflight
- Use a data cable. Many USB-C cables only charge.
- Drivers on Windows. Install the virtual COM port (VCP) driver; for flashing in DFU mode you may need the driver Betaflight Configurator suggests.
- Close other apps that might hold the COM port, and try another USB port.
- Battery off for setup. Plug in USB only, and always take props off before any bench test with a battery connected.
DJI O4 and goggles
With a DJI O4 Air Unit, Betaflight warnings show in DJI goggles only if MSP DisplayPort is set up on the right UART. See Betaflight OSD in DJI Goggles 3. If your DJI ready-to-fly drone (Avata 2, Neo with goggles) won't start motors, that's a different problem: see drone won't take off.
New to the hobby? Read how to fly an FPV drone and FPV terms explained, or browse our FPV gear.
Related guides
- Why won't my DJI drone take off?
- DJI drone won't land or turn off: what to do
- DJI gimbal protectors: when to use them (and when to take them off)
- Analog vs digital FPV: which video system should you choose?
- DJI Goggles 3 vs HDZero goggles: which digital FPV system?
- Do DJI Goggles 3 work with analog FPV?
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