The throttle input is reversed and the failsafe value is on the wrong side

What ArduPilot says:

• PreArm: Invalid THR_FS_VALUE for rev throttle

The throttle input channel is reversed (its RCn_REVERSED is 1). Plane then recognises a lost radio by a pulse above THR_FS_VALUE, not below it, so THR_FS_VALUE must be higher than that channel's RCn_MAX. Here the throttle failsafe is on (THR_FAILSAFE is not 0) and THR_FS_VALUE is below RCn_MAX: ordinary stick positions would be taken for a lost radio.

What to do, most likely first

1. The throttle was reversed in ArduPilot, though the transmitter could have done it (or it was not needed at all).

   CheckRC3_REVERSED (or the channel that RCMAP_THROTTLE names) is 1. In the Radio Calibration screen the throttle stick fully down should read about 1000 µs before any reversing.

   FixSet the direction in the transmitter so that stick down gives the short pulse, set RC3_REVERSED back to 0, calibrate the radio again and leave THR_FS_VALUE at 950.

2. The reversed throttle is intended, and THR_FS_VALUE was left at its default of 950.

   FixMake the receiver send a pulse longer than the stick can give when the link is lost (for example 2100 µs) and set THR_FS_VALUE between RC3_MAX and that pulse (for example 2050).

Parameters to look at

Where to do it:Starting Parameters