What caused the mode change to Loiter? and how to prevent mode change during RTL?

Hi, All

There maybe a problem with RC FAILSAFE RTL, I am using a WFT09 brand RC, when the receiver lost connection with RC, the recerver indicate this event by low the throttle(CH3) below 970, and set all others at MID, this is OK for APM RC FAILSAFE triggering.

The problem is, the moment the copter is losing RC connection(far away), when will be ‘connection TURBULENCE’, that is, the connection may ON and OFF for un unstable moment, chennal output maybe unstable during this period.

I got this LESSON once a time: the copter flew away and a long time not coming back, when I supposed it crashed, it came back— hovering above my head. I checked the log, and found that the RTL mode was updated to Loiter by the mode chennal, and, because this moment the connection is OK already, RC lost RTL will never triggle again, then, the copter was LEFT there, Loitering!!! fortunally, the wind blow it back to my direction, and slow it came back.

After that, I had set the Loiter mode at CH5 MID position, because when I start a auto mission, I always start from Loiter, with CH5 at MID, in this way, even RC connection lost, the receiver CH5 default output is still MID(1500), then the CH5 mode chennal will not interrupt the RTL mode.

I am happy with this setting, untill today, I was flying a copter 3.4.6 PIXRACER, same WFT09 receiver with PPM encoder, about 970m away,
the RC LOST RTL triggled and comming back, but, interruted by not knowing reason, mode to Loiter, fortunaly, I can saw this on telemitry android phone, I use CH8 to force coper to RTL again, and it came back.If I failed to do this, my copter would have LEFT far away, loitering and crash…

Now, can any friend can tell(refer to LOG),
1, what caused the mode change from RTL to Loiter ( I checked and found CH5 no change in MID, my setting is low mid high STA LOITER ALTHOLD in CH5., I use CH8 to trigger RTL forcefully, see attachment, could CH8 MID -LOW edge trigger MODE change from RTL to LOITER? )

2, what is best solution to my above Connection Turbulance Problem?

huilaibianloiter.zip (2.5 MB)


I haven’t looked at the log but from your images it looks like that when you lost RC connection the receiver started sending low values (1000 PWM). When it resumed RC connection it went back to about 1500 PWM, which is seen by the system as a mode change, so it goes back to Loiter.

You should setup your receiver in one of two failsafe modes:

  • stop pulses
  • lower the throttle channel (and only the throttle the channel)

From what I found in the Internet, it looks like you can do the second one with your receiver.

Thank you OXINARF, we may find the problem. but I think the Trigger is CH8 MID-LOW edge, I set CH8 HIGH as RTL for emergence use, so very possibly it is CH8 MID-LOW jump triggle copter to check mode and switch mode back to Loiter.

I test at home a moment ago, and found if switch CH8 to HIGH, mode change to RTL, if turn back, mode change back to MODE setting by CH5, so, I suppose this is the problem.

Now, I change emergency RTL to a 3-band switch HIGH, and intially set this switch at MID, then, even RC lost, default value is MID, and will not trigger any mode change.

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