Watch out for Spektrum "SmartSafe" Failsafe!

[KK1W]

I';m a noob with multi-rotors but I';ve done a lot of R/C over the years. Right now I';m in the process of getting comfortable flying around my yard in stabilize mode. I have been very methodical approaching my multi-rotor adventure and thanks to info and help on this group (among others) things have progressed fairly well. I consciously have not setup failsafe on the FC (Arduflyer 2.5 w/2.8.1 software) as at the moment I';m just flying in my backyard.

So, most of the snow it gone and I took the quad out to get in some practice. I also setup channel 6 to do some PID tuning and was looking forward to burning through a few battery packs. The first pack was a good flight. I landed, disarmed and disconnected the battery. New battery on, quad on the ground, armed and I looked at my TX and noticed the flight timer was not reset because I had not power cycled it. So, I turned if off. 

Holy CRAP! All of a sudden the quad started up and launched itself on the way to the moon.  As I watched it get smaller in the sky I flipped the TX back on and somehow gained control, got it safely down in the yard and went inside to change my pants :embarrassed  Once I got cleaned up I started looking into the reason (beside the fact I must be a moron).

A look at the FC programming with Mission Planner verified failsafe was indeed OFF (it was not configured). So what went wrong? I looked at the log file. There was never a mode change in the FC for the entire flight. It started in STAB and never changed. So for sure it was not a failsafe event as far as the FC was concerned. Graphing out Throttle IN, Throttle OUT and BARO ALT it was very obvious the throttle channel went to 1000 - so that had to come from the TX. Brought up the Calibrate Radio screen in MP, put the throttle stick down and turned off the TX. About 2 seconds later the throttle slider went to full power!

The problem turns out to be Spektrum';s SmartSafe failsafe. Upon binding the position of the throttle stick is remembered for failsafe (not the others). If signal is lost the RX returns the throttle to the bound setting while maintaining the last known stick position for the other three channels. Apparently when I bound the RX the throttle stick was in the full up position. Dammit! (my guess as to WHY the stick was full up was I was also going to calibrate the ESC';s - but who knows for sure, that was a few months ago)

Anyway, the takeaway here is that, even though I never setup failsafe, it still happened. The way to catch it would have been to watch the calibrate screen in MP and turn the TX off. Just because you never ';setup'; something doesn';t always mean there won';t be an ';event';!

The good news is, besides uttering some choice words and changing my shorts there were no injuries nor a destroyed quad. But what if I was standing over the copter when it happened? 

Oh yeah, and I never turn off the transmitter when the system is armed anymore either! 

Hopefully someone can learn from my mistake.

[teslahed]

Well that sounds dramatic and scary - well done getting the transmitter turned on and the quad back under control!

Thanks for reporting back as well - hopefully save someone else with a spektrum transmitter the same problem.

[Gaza07]

Thanks for letting us know KK1W    also if you reverse your throttle after binding in failsafe it will revert back to the other way 

[KK1W]

Thanks for letting us know KK1W    also if you reverse your throttle after binding in failsafe it will revert back to the other way 

Gaza,

Hey, that must be how it happened! Thanks for bringing it up.  I use a Spektrum module in a Futaba 9C. Throttle is reversed in Futaba world. I';m thinking now it was down when I bound the RX, then when I configured the model I reversed the throttle. The rest is now, as they say, on it';s way to the moon!

I still feel like a moron but at least I';m pretty sure now I didn';t bind with the throttle stick all the way up!

Good catch and one more variable to try and keep track of in the future.

[KK1W]

Well that sounds dramatic and scary - well done getting the transmitter turned on and the quad back under control!

Thanks for reporting back as well - hopefully save someone else with a spektrum transmitter the same problem.

Thanks Chris but it was pure luck getting it back down. The log showed it hit 50 meters AGL before I regained control. 

The problem lies both with the RX and the Futaba TX. There seems to be no way to disable the SmartSafe in the RX (It is a Spektrum AR7000) combined with the reversed throttle function in Futaba and you';ve a formula for bad things happening. Like you say, if it helps just one person avoid the problem it was worth writing up.

[peter_a]

I guess that`s the big advantage of the controller with arm and disarm .
If you throttle goes high in disarmed mode it just gets ignored !!!!.

[bunnygirl80]

Hi KK1W,

I thought I';d let you know, there are two ways to bind the Spektrum SmartSafe receivers. You can bind them to remember the throttle position only OR you can bind them to remember all channels. The standard method and the method known to most fliers is the first where the throttle only is recorded during bind.

NOT MANY PEOPLE KNOW THIS... as someone once said. If you want to bind and for the receiver to save all switch positions. This is something you almost always need for Quad failsafe, even if you';re using MultiWii or Naza. This is how you do it.

1. Plug in your bind lead into the Spektrum RX.
2. Power up your RX.
3. The lights on the RX will flash.
4. IMPORTANT... Remove the bind lead (yes, remove the bind lead).
5. This will put the RX into SmartSafe Record all channels.
6. Set all your TX throttle and switches to the correct place for failsafe.
7. Power up your TX with the bind button in.
8. Turn all off after the bind is completed.

Step 4 is the different one and also the important one... I hope this helps you set up your failsafe.

Stef