Hi Everyone.


Recently got into ArduCopters, and have a standard 3DR frame with the 850 motors, APM1 etc. Radio I use is a Spektrum DX8.


Being a total noob, I have been the cause of a number of crashes and I can live with that, however for the second time now, my quad has just fallen out of the sky. It was flying quite stable (2.5.1) and alt-hold, loiter and RTL all worked quite well, although I do have some yaw issues, but I will save that for another day.


What happend today and also about 2-3 weeks ago, is that it's flying along as expected, responsive etc, and then nothing, not throttle, I could see the props stopped, turned turtle, and met the ground with some force, damaging all four motors. Luckily I learnt from last itme and bought one of those boxes which protected the APM.

Also since the last crash I have moved the power to a different ESC.


So it's the same field, and was about the same distance away from me (about 150-200 meters), when it crashed. Looking at the logs, you can see the Throttle, Pitch, Roll in all just die. Could it be a range issue?

.log file and a pic of the graph attached.


Appreciate any help!

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I am looking into that now.  I want the Failsafe to be my RTL.  It is a little scary knowing that I really don't have a Failsafe.

But if you can't program it in the actual radio, then you can program the RX different?

The way it works is that, with the aircraft on the ground, no motor power, you put your radio in the condition you want the failsafe.  So, all sticks at neutral, and RTL mode selected.  Then you push a button on... I think it's on the Rx, and it beeps, and that means you have saved that failsafe position.  Simple as that.


I have the same Problem like you, and i have a DX8 too.... :/

But this error i have only 2and time! I fly now over 3-4hours with my new APM2.0 from the V2.4 -> 2.5.3, have no problems like this....

And i hope i dont have this "error" in high altitude ....


Is the APM fail safe not when you set the rx to output less than 950uS. That way the APM knows it's all gone Pete Tong and  it needs to do what you preset i.e. RTL. it's got nothing to do with channel 7.

Just found it: http://code.google.com/p/arducopter/wiki/AC2_Failsafe

To enable failsafe, set the parameter THR_FAILSAFE to 1 (0 = disabled).

If you have enabled and triggered failsafe, your copter will rise 10m, RTL back to home, and auto-land after 20 seconds.

For safety, Failsafe RTL will NOT engage unless you are Armed and at least 10m from GPS home. Even with these requirements, you must remain diligent when using failsafe. It is likely you may accidentally trigger failsafe by turning off the radio accidentally. This may cause the AC to lift off and hover 10m above it's current location.

Failsafe is triggered when your receiver outputs a low throttle signal (below 975µs by default). This can be done by looking at the Status or Raw Sensor View (Radio) and changing the end point on your low throttle setting so that it is below 975µs. Then programme that into your receiver as a Failsafe setting (refer to your receiver's manual). Then reset your low throttle setting back to what it was e.g. 1100. Test that the receiver Failsafe setting is working by viewing the radio data as above and then switching off your Tx. The Ch 3 setting should now drop to the below 975µs setting. Switching the Tx back on should restore the Ch 3 setting to your normal neutral throttle value. Recalibrate your radio settings once you have completed this exercise.

Once you enter faIlsafe, the copter will rise 10m above it's current altitude to avoid obstructions as it flies home and auto-lands. You can recover the copter in the air when you regain the radio link by switching the flight mode switch.

There are two options for failsafe. If you are in Auto and prefer to continue your mission, the parameter THR_FS_ACTION should be set to 1. If you prefer to have the copter RTL even if it is flying under autopilot, set THR_FS_ACTION to 2.

That seems like the APM failsafe? 

I could also be on totally the wrong track...

Interesting find Crispin, I thought I had read that before, so to me this is a APM failsafe. Will look at this in a bit more detail tomorrow. 

Also did some testing with range again, and compared to another DX8 radio and similar set up we got similar results more inline with what I was expecting.  The only other thought with regards to range, is that there is a phone cell mast about 100 meters behind me where I have been flying, so this could be part of the issue .

Will try and fly again tomorrow but from a different field.

Thanks for all the responses, lots to think about.

So for the benefit of others, Tony and I live about a mile apart. 

We were pondering a few minutes ago about where he was flying. It's a farmer's field but the corner where Tony was has a cell tower not that far from it. Maybe 100m or so from where he was flying. One of the antenna on tower was facing towards where he was flying. They are slightly directional I assume as there are 3 on the tower.

Rough idea:

Could the proximity of the tower have caused the rx to loose touch? It would have been about equidistant between him and quad and him and cell tower.

GSM only goes from 900 to 1900 so a fair gap (unless some harmonics are involved?) but could it just have  drowned?

Just thinking out loud.


I'd say it's unlikely.  Phone towers are relatively low power and spread across a band.

If it was a TV, FM or AM broadcast transmitter, then I'd say yes.  I've had my GPS clobbered when within about 500m of a TV tower.

Right following ion from Crispin's blog post here http://diydrones.com/profiles/blogs/spektrum-dx8-and-ar8000-failsaf... , I set up the failsafe and went to test.....


Mixed results, really.


Quad was very stable all round, Alt-Hold, Loiter, RTL and auto land all worked well. No issue with those.


As far as the failsafe test goes... well it works, but the end result was the same... 2 maybe 3 motors bent :-) However, it did try to RTL, headed back to the launch position then it tilted and at that point I panicked, switched the radio back on, and crashed.

Very cool, and not bothered by the crash as I was kinda expecting that, but I won't be testing that again. If it happens in real life, I know the backup mode is there and will deal with it on the day. Hopefully have enough time to recover if/when it comes back into range.

Well bumping a old thread of mine as I still seem to be struggling with the quad dying on me and crashing. I am now running a APM 2.5 version 2.9.1b

Been playing around with Auto flight modes over the last few weeks, and I have had mixed results.

First test, I set a planned flight and set the quad off. It completed the flight ok, and landed pretty much where expected. After a few minutes I then started the mission again, and when it got to the furthest point away, it lost all power and dropped out the sky. Fortunately some stinging nettles broke the fall, and apart from a nicked prop no other damage.

Looking at the logs and KMZ files, it seems it was flying fine then FS, and then it went into stabilze mode...

First flight, completed ok.

Second flight crash:

Log file:

So onto another day and a different flight plan (and location), and again first flight was fine, returned and landed as expected, however second flight ended in a crash.

First flight OK:

Second flight crash (excuse the crude writing):

Log file:

This is my failsafe settings:

What I don't understand is what is triggering FS. Will this only happen if radio range comes in play? Looking at the second crash, it does look like it FS to RTL (which is what I set it to do), but why did it loose all throttle? I may have panicked and kicked in the final Auto mode, but I doubt it. 

Would appreciate any thoughts on this.

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