Failsafe doesn't trigger LAND whilfe flying in LOITER

Hi guys,

I'm using a Pixhawk with AC3.2-rc10 and ran into problems while setting up the throttle failsafe function. I followed the instructions on the wiki page and everything works fine and as described on that page while being in stabilize mode. So the copter switches to LAND when the transmitter is being turned off, motors run for approximately 5 seconds and then the copter disarms (propellers are removed and the copter just sits on my desk, I haven't tested it "live" in the air yet).

But my problem is, that when I turn off the transmitter while being in loiter mode, the flight mode displayed on the MP failsafe page stays "loiter" and motors immediately disarm, which would propably lead to a crash, while being in the air and loosing transmitter connection.

So I'm wondering, if this behaviour is normal. Shouldn't the copter change it's flight mode to land from loiter the same way as from stabilize when the failsafe is triggered? The wiki page doesn't give any information about this.

Thanks a lot in advance. Would be nice to get some thoughts about this, since I'd like to have the failsafe working properly before I'm going to let my little monster take off. :D

L.B.

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  • shame on me for not guessing you might be trying that without GPS :)

    • GPS was 3D fix at the time, I did the test. ;) Although GPS precision and accuracy seem not be very good at the moment, but thats another story...

      But I discovered another little issue with the failsafe especially with the battery failsafe. I wanted to deactivate it, so I changed the FS_BATT_ENABLE value to 0 (disabled), but anyway experienced a failsafe event triggering when voltage dropped below the threshold defined in the FS_BATT_VOLTAGE parameter. Only when I additionally changed the FS_BATT_VOLTAGE value to 0 the battery failsafe event didn't occur.

      It's no real problem, but in my opinion a bit counterintuitive. It would be better to beeing able to disable the whole battery failsafe feature by just changing the FS_BATT_ENABLE parameter to 0 no matter what the value stored in the FS_BATT_VOLTAGE parameter is. Just my opinion although I cannot be absolutely certain that I didn't make a mistake in the setup (arducopter greenhorn at work... ;))

  • Developer

    Ok, the web page is slightly out of date.  This is what is says:

    When a throttle failsafe is triggered one of the following will happen:

    • Disarm motors – if you are in stabilize or acro mode and your throttle is zero
    • RTL – if you have a GPS lock and are at least 2 meters from your home position
    • LAND – if you have no GPS lock or are within 2 meters of home when the failsafe triggers
    • <snip>

    In fact what you're seeing is the top response.  It's because the vehicle is landed (on your bench) in Loiter mode so it immediately disarms.

    Thanks for the report, I'll update that line in the wiki.

    • Thanks a lot, Randy. I should have tested it in the air, but I wanted to ensure that everthing works properly before doing so.

  • Are you saying something else happens if you switch off tx in stabilise or other mode ?

    It is not flying, then it's not landing, sounds like expected behaviour when on your desk.

    • Thanks for your answer, Andre. And yes, the behaviour of the failsafe between stabilize and loiter is definitely different. When the copter is in stabilize and the TX being turned off the flight mode on the failsafe page changes from "stabilize" to "land" and the motors slowly lower their speed to the minimum speed and after that the copter is being disarmed.

      In contrast to that the flight mode doesn't change while triggering a throttle failsafe in loiter and the motors stop directly and the copter is being disarmed. I also tested moving the copter round while being in loiter, but the behaviour stays the same.

      So in stabilize the failsafe is working absolutely fine, but in loiter triggering the throttle failsafe would probably lead to a crash, since motors would just stop running.

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