Hazardous fixedwing failsafe motor behaviour

[rts18]

Current Behavior

I inadvertently flew into a region of elevated RF noise. This caused the GPS to loose satellite coverage and the radio went into failsafe at the same time.
When failsafe takes over using failsafe_procedure = RTH. It disregards failsafe_throttle = 1000 and throttle_idle = 0.000 with airmode disabled. And continues to run the motor at idle during the emergency landing procedure.

I have encountered this before on a single motor airplane. But not with a twin motor until today.
The unfortunate part was only one motor continues to run, while the other stops. This caused the airplane to spiral into the ground. Instead of a circular descent landing.

The motor mixer is configured correctly for operation. The ESCs have worked correctly in flight previous to this event. Both motors are on the same timer using Dshot300.

When I got home I tested another twin motor airplane to find what went wrong.

Steps to Reproduce

1. Have your plane powered on the bench with a battery and NO GPS fix
2. Have the motors running at what ever throttle
3. Turn off the transmitter or use FS test mode
4. One motor stops and the other continues to idle high using the aforementioned settings.

Expected behavior

Both should obey failsafe_throttle = 1000 and stop the motors in a fixedwing spiral emergency landing.

• FC Board name and vendor: Tested with a Matek F405 and H743
• INAV version string: 10.0 RC1

[breadoven]

Have you checked the log to see what's being sent to each motor when this happens ?

[rts18]

When failsafe = ON with EMERGENCY_LANDING_IN_PROGRESS. Motor 1 = 24% and motor 2 = 0%.
I'm not sure where 24% throttle for motor 1 is coming from.

[breadoven]

When failsafe = ON with EMERGENCY_LANDING_IN_PROGRESS. Motor 1 = 24% and motor 2 = 0%. I'm not sure where 24% throttle for motor 1 is coming from.

Does it have differential thrust set ? Diff would be useful.