Can I bench test the Failsafe?

Good day,

I have completed the assembly and setup/calibaration of my first quadcopter,

Plan a test flight this weekend.


Failsafe action = 2.

DX8 - followed the post to calibrate the failsafe. Looks good.

On the bench, without props I noticed the motors increased in speed when I shut off the transmitter.

Now I'm worried that it will take off if I try this in the field.

I assume it is trying to climb to 10 meters before it can RTL.

Is there a method to bench test the failsafe?




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  • I saw the same effect on our test quad.  Motors spun up when sitting on the bench when the radio was shut off.  The correct low throttle was received around 950.

    When I tested in the field I first wanted to see what would happen based on the bench results as this seems to be a safety issue. APM 2.5 with firmware 2.7.3

    With the copter sitting on the ground armed but with motors off I shut off the radio.  The copter did climb, in a shaky manner unlike normal flying, to about 10 meters then after a second basically fell at a rapid rate to the ground. The test was on a almost indestructible frame with some extra "shock absorption"  measures in case of the worst so I was not concerned about the copter which suffered no damage - but this could hurt someone accidentally turning off the radio.

    Perhaps there should be a check in the loop that prevents fail safe actuation of the motors are already off.  While one should not turn off the radio before powering off the copter it happens sometimes either through ignorance or a mistake.

  • The way I tested (after I had some scary moments field testing) was to load a backed-up configuration into a simulator model with FlightGear. This let me test the failsafe with hardware in the loop. Granted, it isn't an exact test since you have to flash the simulator firmware instead of your actual quad firmware, but it at least let me see what happened with my radio and configuration settings in the simulator, and it let me track down an issue with the configuration.

  • Developer

    We were actually discussing this very issue on this week's dev call..the need for an easy way for people to check their failsafe and know what happens.  Anyway, as Jason says..checking the radio input (either through the cli or as you have through the mission planner's radio configuration screen) is a good start to know whether it will be activated..but there's no super easy way to know exactly what action will be invoked on a failsafe (i.e. RTL or not).

  • Developer

    If the motors spin up they are probably trying to gain altitude.

    Try this: open the Serial window of Arduino and run the CLI.

    There is a test called PWM. Run that to see the raw PWM output. 

    Turn off the radio and note what it does. It should drop below 975.

    If it goes higher, well,  you have problems with your radio setup.


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