I flew my first apm flight today and noticed a possible error in the way fail safe and circle mode works. It almost resulted in the loss of my aircraft.Firstly, does circle mode circle around the GPS location it was engaged in? Or does the circle just drift with the wind.Today I flew out of range of my RC Tx as a test and was already out of range of my ground station (so we couldn't see the plane on the screen). Circle mode engaged after 1 second of RC Tx loss, but when it re acquired my Tx signal, it did not go back into Auto mode, instead, it continued to drift downwind circling, seeming to not enter RTL after 20 seconds because the Tx signal was re acquiring, then getting lost during each circle. Finally it hit 20 seconds of no RC Tx signal and commenced RTH, but when it re acquired the signal this time, it went into auto mode and tried to continue the mission. At this point, it flew out of range again and the same process started again.I managed to get the aircraft home by forcing an RTH whilst I had RC signal.Testing shows that it will go from circle mode back to auto mode if I jump to stabilize then back to auto.Remember that the whole time I was out of range of my 433mhz ground station, so we couldn't see the plane.So in brief,1) circle mode is not able to automatically resume auto mode when it re acquires RC Tx2) circle mode seems like its not based around a GPS point and drifted the circles in the wind (did I say it was 20 kts breeze).3) after it did the 20sec RTL failsafe, it went back into auto (should it continue home?), and then flew the mission until it hit failsafe againlastly, in mission planner, the 1 second failsafe drop down menu shows one option of RTL even though the action is actually circle mode.I believe, that the action in event of a 1 sec failsafe should actually be loiter.Hope this all makes sense, or someone can tell me I'm wrong about how it works, but seemingly my tests showed that the aircraft can potentially be blown away. My plane drifted about 1km downwind and out of my sight during this test.I have afew other questions, but I'll post them in the appropriate place in these forums.ThanksMatt
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Matt, On the intended behaviour of CIRCLE you might find this useful from the 2.69 release notes, Paul
'Another significant change in mode behaviour is that CIRCLE mode now holds altitude. This is important because CIRCLE is used in the first stage of failsafe conditions, and if your plane is badly trimmed it could lose quite a lot of altitude before the RTL stage of failsafe kicks in. Note that this doesn't mean that CIRCLE is now the same as LOITER - in a LOITER the plane will adjust its roll to keep going around the target position, whereas in CIRCLE the position of the plane isn't considered - it just holds a small roll angle, which results in a large circle that drifts with the wind. This is deliberate as we want CIRCLE to not be dependent on the GPS, and to involve no sharp turns.'
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'Another significant change in mode behaviour is that CIRCLE mode now holds altitude. This is important because CIRCLE is used in the first stage of failsafe conditions, and if your plane is badly trimmed it could lose quite a lot of altitude before the RTL stage of failsafe kicks in. Note that this doesn't mean that CIRCLE is now the same as LOITER - in a LOITER the plane will adjust its roll to keep going around the target position, whereas in CIRCLE the position of the plane isn't considered - it just holds a small roll angle, which results in a large circle that drifts with the wind. This is deliberate as we want CIRCLE to not be dependent on the GPS, and to involve no sharp turns.'
HI Matt,
Thanks for the report, that does indeed sound like a bug. I'll have a look at it for the next release.
Cheers, Tridge