No frame from the receiver in time (ERR RADIO-2)

What ArduPilot says:

• ERR RADIO (Subsys 2)

The log's RADIO error has one code, 2 (late frame): no valid frame came from the receiver for RC_FS_TIMEOUT seconds (1 by default) while the radio failsafe is switched on. It is written at the moment the radio failsafe starts, so “ERR FAILSAFE_RADIO-1” and the message “Radio Failsafe” follow it at once. A radio failsafe without this error started the other way: frames kept coming, with the throttle below FS_THR_VALUE.

What to do, most likely first

1. The link was lost: the receiver stopped sending frames, or flagged its own failsafe.

   CheckLink quality and RSSI in the log fall in the seconds before the error.

   FixFind why the link dropped (range, antenna placement, the transmitter's battery) and repeat the bench failsafe test before the next flight.

2. The receiver's power or signal wire is intermittent, so frames stop without any fall in link quality.

   FixRe-seat or solder the receiver's connector and secure its wires; check its 5 V supply under load.

Parameters to look at

Where to do it:Failsafe ExplainerSetup & Tuning Guide