Naza M Lite failsafe issue?

[Dickw]

I am new to DJI products and have a query about failsafe following a recent incident with my F450 Flamewheel fitted with a Naza M Lite.

I flew around for a while until I found I needed to keep the throttle almost fully open to stay up. Assuming that was because the battery was nearly discharged I came back near to myself to land. I have failsafe set to “landing” so I thought I would switch to failsafe and see if it really would land itself â€" didn’t work like that!!!!

The quad immediately shot upwards at high velocity â€" instinctively I switched back to normal and closed the throttle - the motors then stopped so the quad started to fall from a considerable height. I managed to open the throttle again in time to slow the impact, but even so it bounced and landed again upside down. Happily  it still works OK, and the only damage was to my ego at the sound of my friends laughter  .

Did I miss-understand how failsafe works, or do I have a fault to find?

You can see the curent (red line) and throttle channel (blue line) from the logs, and I didn't lose Tx/Rx link at any time either.

Dick

[ched]

I think the failsafe is set to automatically rise to 20m then fly back to the landing position. So your quad just opened throttle to climb to 20m to then fly back to the take off point and land. I believe in the configurator it has a picy of the quad climbing then coming home.

Silly question but you do realise if you discharge the batter too low you will damage it!!!!

I thought there was a setting within the configurator to have battery warnings via the LEDs?

You really need to have a battery warning of some sort. The cheapest are only a couple of quid and clip onto the balance port of your lipo. Then when voltage gets to a lower limit it beeps.
Best way is to have an alarm set on your tx with flight battery telemetry.
For a really simple way is to time a flight then check battery voltage if it's higher than limit have a bit ore of a fly and check again. A rested lipo cell should be about 3.7v for each cell.

[Dickw]

Well there seems to be two failsafe options:-
a)   Landing
b)   Return to home then land
I can understand why it would rise up if it was going to return home with option (b), but I have option (a) selected so was just expecting it to land â€" am I wrong?

Don’t worry about the Lipo I have been using them for years (but you were right to point out the risks  ). Yes, there is a LED Lipo warning but I have set that very low and instead use both voltage and capacity telemetry plus voice alarms in the Tx to warn me. Lipo immediately after flight was 11.3v = 3.75v per cell, and just checked it now 3 days later at 3.79v per cell.
It’s just how DJI works that is causing me problems  .

Dick

[ched]

It is a while since I used the config so I forgot about the 2 methods. In that case I have no idea.
How did you switch to failsafe, did you turn tx off? If so how is rx failsafe set?

[Dickw]

It will go to failsafe if I switch off the Tx (I did test it on the ground), but I also have failsafe on a switch and used that in this case â€" works the same in ground tests.

Just thinking over what happened and looking at the logs, I have a theory :-

I don’t think I have the voltage alarm set low enough in the FC, so as the battery voltage dropped it started to lower the power as a warning. Unfortunately, I knew from telemetry that the battery was still OK so just kept opening the throttle to compensate.
The FC and I were fighting each other.
So, when I switched to failsafe the FC forgot it had been lowering the throttle itself and just looked at my near full throttle with the results you see in my log extract in the OP.

Does that make sense?

Dick

[ched]

Does make sense as the rx would have had high throttle signal. So therefore last throttle signal before failsafe would be high throttle but when failsafe is triggered by tx I have no idea how the FC reacts.

[Dickw]

OK then - next outing I lower the voltage alarm in the FC to a point it will never see in flight so it can't interfere with what I am doing. I then trigger failsafe in flight again and see what happens - at least I will be prepared for excitement this time. I will report back on what does happen.

Thanks for responding.

Dick

[Dickw]

This time everything went as expected. Triggered failsafe in a hover and the F450 stayed where it was for a few seconds and then gently lowered itself to the ground.

My conclusion is that my earlier "issue" was indeed down to my having the throttle fairly high in the hover without realising I was fighting the FC which was trying to land it - when I switched to failsafe it saw the high throttle and shot up before it got round to trying to land itself  .

we live and learn.

Dick