With an 18MZ and a 7008SB, you can set individual failsafe behavior by channel (I believe a number of receivers can do this).
So instead of making my PPM encoder and APM figure-out it lost radio contact, I did the following setup with my Futaba failsafe:
All sticks to neutral
Channel 5 to Alt-Hold level
Channel 6 to neutral (used for gain adjustment)
Channel 7 to off (used for random things)
Channel 8 to active – which is always used for RTL
So if the radio goes dead, you’d expect the RTL signal on channel 8 to override everything else and put the copter in RTL mode. But in testing on the ground, the mode was set to Alt-Hold about 75% of the time and to RTL about 25% of the time.
A few hours later, I tried something: By disabling the failsafes on channels 5-7 all together (just go with the switches as they were – essentially a “Hold”), powering-off the receiver always sends it to RTL mode. I don’t understand why, but it’s almost as if the artificial receiver Alt-Hold signal (channel 5) and RTL signal (channel 8) were competing with each other.
Anyone know why it would do this? It isn’t really a problem (since I fixed it), but it sure does seem like peculiar behavior.
Channel 8 to active – which is always used for RTL
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If it does the above all at the same time it might depend on where ch 5 was in the first place. For instance if it were already in alt hold then the only mode change would be to RTL on ch 8. However if ch 5 was in say stabilize mode then when it went into failsafe it would effectively be flipping ch 5 and ch 8 at the same time. Whichever the pixhawk sees as the last thing would be set. I could see how this might not be consistent. Maybe if you just eliminate the failsafe from doing anything with ch 5 then you would know it will for sure only do ch 8 to set RTL. Alt hold isn’t needed as you can set the default RTL altitude in the params. Just my guess
Channel 8 to active – which is always used for RTL
[/quote]
If it does the above all at the same time it might depend on where ch 5 was in the first place. For instance if it were already in alt hold then the only mode change would be to RTL on ch 8. However if ch 5 was in say stabilize mode then when it went into failsafe it would effectively be flipping ch 5 and ch 8 at the same time. Whichever the pixhawk sees as the last thing would be set. I could see how this might not be consistent. Maybe if you just eliminate the failsafe from doing anything with ch 5 then you would know it will for sure only do ch 8 to set RTL. Alt hold isn’t needed as you can set the default RTL altitude in the params. Just my guess [/quote]
I believe that’s exactly what is happening. What I need to try to test that theory is to fly in one mode (i.e. Stabilize) and flip the RTH swtich. Then, a second or more later, flip the “Alt-Hold” switch.
Based on what I’ve seen and what you’ve speculated, that second switch flip should over-ride RTL mode and put it into Alt-Hold Mode.
I’ll test it one day when I have adequate light and weather.
Yea it will for sure go back to alt hold. RTL is like all other modes in that it will only stay in that mode until another mode is called for. Also… in my case I have RTL on ch 5 which is only a 2 position switch. If I flip it from ON to OFF it will go back in whatever mode it was in before it got turned ON.
