Tested failsafe with a not so good result...

E

europe

Member
Hi everybody,
today I decided to test failsafe for the first time. I flew away about 100 metres and "parked it in the air", then flipped the fail-safe switch at about 5 metres altitude. It started by descending a meter or so, then went up to 20 metres, turned towards the take off point and came back. Waited for some time at 20 meters altitude and the started to descend. Fast.:livid: Actually since I never had seen it perform this I didn´t know what to expect and by the time I realized that it would hit the ground in a not very controlled manner it was too late. It was not that it turned off the motors 20 metres up, but it didn´t seem to give enough throttle to descend slow and easy. The quad hit the ground hard enough to let the propeller protection ring hit the props and both the protection and my new Tiger carbon props were destroyed. Luckily the cameras did survive.

After a few seconds on the ground the motors were revving up again and it did a few jumps before it settled. Quite scaring actually as the whole fail-safe operation not seemed to be performed under control at all :confusion:

I did have a good and solid satellite status and no error messages/codes. I had just flown two full batteries using GPS, IOC etc. without any problems. My radio is a DX8 and I programmed the fail safe function for TX lost with 50% throttle even though I guess it doesn´t matter since the Naza takes over control? The fail-safe switch have been verified functioning for all flight modes prior to this test in the software assistant. Battery status was good (verified with both timer and OSD).

I got the impression that the Naza miscalculated either the starting point altitude or that the quad was too heavy to slow down when it came closer to ground. It feels like I have enough powerful motors when I´m flying and they do not get very hot. It is consuming around 30A when hovering and I use a Zippy 3S 5800mAh 30C battery. The quad is a 500XT with Tiger motors and an all-up-weight of about 2 kg.

I have Naza-M GPS v1 with firmware 3.12

Any ideas what might have been the problem or seen anything like this before?
 
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Tomstoy2

Tomstoy2

Member
GPS calibration, especially z-axis. Jumping on the ground is an indication, thinks it hasn't come close to the ground yet. Z-axis is critical. Make sure you know how to bail out of failsafe, ( flip off failsafe, then toggle mode switch out of gps and back into it ).
 

E

europe

Member
Ok, by GPS calibration you mean the Naza dance? I didn't get any indication of GPS or compass problems. The quad was rock stabile both in position and direction and I left it hovering for about 30 sec. to wait for a passing car just before I engaged fail-safe. It performed a perfect position hold at 5 metres altitude during this time with absolute no stick input from me.

How can I tell if and when I have a z-axis GPS problem?

Good to know there is a procedure for bailing out of fail-safe. I tried just to flip the FS switch back, but seemed to gain no control of the aircraft as it bounced around with damaged props. I never flipped the flight-mode switch which was left in GPS during the whole flight. And, by the way, there was no wind at all.

I definately need to find a reason for this minor crash before I try FS again. I am planning to use my quad for AP and the national authority demands a functional fail-safe function in order to grant the necessary permission.
I am learning all the time... :)
 
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Tomstoy2

Tomstoy2

Member
No, the dance is compass calibration. I'm talking about xyz set up for the gps. To figure z setting for the naza you must figure the balance point when the multi is stood up vertically on its side. Have everything on the frame, battery, gimbal and camera, if you use one, and figure out exactly where the balance point is when stood up on its side. Then measure how many cm it is from the balance point to the center of the imu. There are several boobtube videos out on how to determine this. Care must be taken in entering the figure as either positive or negative entry in the data field. Review the manual again, watch the vids and then redo your figures.
 

OneStopRC

OneStopRC

Dirty Little Hucker
Question I have is... How much weight has this bird got on board? I have not tried my fail-safe since removing the battery fail-safe auto-land feature due to the way it came down last time. GoPro and landing gear made it fall faster then normal, the naza has NO CLUE how fast it descends and really does not care. Mine hit the ground very hard, but my landing gear absorbed the impact.

I wonder why, the Naza has a fixed rate of decent? why can't it calculate based on the barometric sensor how quick it is descending and make adjusts on the fly.
 

E

europe

Member
My quad weighs 2150g and out of this about 450g is camera equipment. I used 11x4.5 Tiger CF props which gave me plenty of lifting power.

I will double check the balance point which I guess is the same as COG?

I also got the impression that the descending from 20 metres was simply too fast to recover.

Thanks for your input! Still puzzled...
 



OneStopRC

OneStopRC

Dirty Little Hucker
I am going to retract my statement about the autoland, I grew some balls and tested it yesterday... 2 times and it is working fine now.

Anyway, my F550 loaded without a GoPro is 4.3 Lbs or 1.95 Kgs. I get about 8 minutes of flight using 2 2650 3S 25c lipos in Parallel. You're not much heavier than I am, and right now on the F550 I have standard motors, standard 30 amp ESC, standard 10" props, landing skids, Naza with GPS. My 2 batteries way in at 15.0 oz 3S 2650 mAh, my 4S 4500 mAh weighs in at 1lb 1.4 oz and does not seem to give me anymore flight time at all.... reasons are weight related and how much this thing can lift or a power to weight ratio. There is a very thin line with batteries and airtime, some think a bigger battery will keep them airborne longer. In some ways it will, if you have the right motors and props to do the work of lifting the weight. Sounds like you might need to figure out motor and prop size for a heavy lift project.
 

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