Problem with Hexacopter using APM 2.8


I recently purchased a Tarot 690s hexacopter , it was partially assembled (e.i the ESCs and UBEC were already soldered to the PDB). The Flight controller is an Arducopter APM 2.8 and the TX/RX combo is The RadioLink AT10 and RadioLink R10D. The problem I have is, upon take-off the copter immediately tips over backwards and the rear props hit the ground. I've tried everything I can think of. Double checked the props and motor rotation, the signal inputs and outputs,  everything. Reinstalled the firmware for the APM. Updated the firmware for the transmitter. Still, nothing worked.One would think that you could just trim something like that out with the Transmitter, but I tried it. This led to the discovery that the copter isn't responding to any input other than the throttle. It doesn't respond to the yaw, pitch, or roll inputs from the transmitter. Nor does it react to its own internal gyros or potentiometers, when you tip or rotate it manually. Nothing but the throttle. In mission planner it shows the the transmitter is sending all of the signals to the apm, but it doesn't react to them. I don't know how to fix this at all.

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  • Darius, that is really good news.  That's why I always land and take off in Altitude Hold mode.  It's hard to manually control altitude on a heavy copter.

    Regarding the Headless mode (they call it Simple and Super Simple mode), you can set that up as a Channel 7 option using Mission Planner on the Config/Tuning, Extended Tuning page.  Alternately you can set it in the Full Parameter Tree page, Ch7_Opt.  3=Simple mode, 13=Super Simple Mode.  Simple mode is OK for beginners, but you will want to move beyond that soon and learn to fly in normal mode. 

    Let us know how it goes.


    • I can already fly in normal mode Xp. I have a little quad that I've been flying for a while that doesn't have a headless mode. I just  didn't know that the simple and super simple meant headless. So  I was trying to control the copter as if it were facing me. I'm going to get a FPV setup here eventually I'll be sure to share videos. Thanks for all your help, and the landing tip.

    • Congratulations, I'm glad you got it working.  If you haven't already, you should spend some time reading through the copter documentation on the wiki  It will help you understand more of the details.  The parameter page,  will give you all of the details on the copter parameters.  It is helpful for fine tuning your copter behaviors.  

      Can't wait to see some of your pictures. 


      Copter Home — Copter documentation
    • Hi Doug.

      So I was able to get out and fly the copter yesterday, and I noticed that it flies smoothly in Stablilize mode but in Altitude hold and loiter modes it sounds very twitchy like it's constantly adjusting, is this something that is normal?

      Also with a 10000mAH 4S battery that discharges at 10C, is there a way to calculate how long it should last?

    • Additional note:  I was wrong about the altitude hold.  It does not use the GPS at all.  It uses a combination of the barometer and accelerometer to determine altitude.

    • Update. I've flown a few times...and crashed into a tree once, lol, it came out of nowhere. Anyways the damage from the tree-crash gave me an excuse to buy retractable landing gear as a replacement. I also ordered an FPV setup as well, which I've tested but have yet to install on the copter, but that's for another time. The landing gear is what I can't seem to get going. I've gone through the on-site copter documentation and it points out some parameters that don't appear in my Mission Planner Full Parameter list.

      I can see that you're supposed to set the landing gear on one of your AUX channel but on my Transmitter my AUX channels don't do anything. They seem to be disabled somehow. So I can't Extend my landing-gear or do the Autotune that you mentioned in a previous post.

    • Do you have and 8 or 16 channel receiver?  If you only have 8 channels, then you are limited to what you can do.  I only have an 8 channel receiver.

      1-4 - RPY and throttle

      5 - flight mode

      6 - dedicated to tuning

      7 - can be set to several different functions, camera trigger, etc.

      8 - Return to Launch

      If you have more than 8 channels, you should be able to configure one for landing gear.

      Sorry I can't say more.  I'm not home so I can't connect, and I don't have any experience with landing gear.


    • Darius,

      In Position Hold mode the copter will try and hold a GPS position.  If the GPS signal is not rock stable, then the copter may appear to “twitch” a little as it hunts to hold a moving target.  I would not expect that exact same behavior in Altitude Hold however as the copter is only responding to changes in barometric pressure and some percentage of GPS altitude data.  The horizontal GPS data is ignored and the copter will just drift in the wind.   The fact that it is stable in Stabilize mode suggests that the Inertial unit (accelerometers and gyros) are all working fine.  So I would be inclined to think it is just GPS position errors that are causing the twitching.  My copter does the same thing in Position Hold. It moves around by about a meter or so.  Look at the Hdop parameter on your mission planner.  Hdop is an estimate of Horizontal Degradation Of Position based on the number of GPS satellites, their relative positions in the sky and the signal quality.  There is a parameter that sets the minimum acceptable Hdop to arm the copter and I believe it’s around 1.2.  I routinely see 0.8 or lower on a good GPS day.   Unless your copter is jerking around like crazy, I would say you are OK.  BTW, I just looked at the telemetry log you posted the other day, and you only had 7 to 8 satellites and hdop was runnig 2 or greater.  That would explain the twitching you were seeing.  You must have the GeoFence disabled, otherwise the copter would not arm under those conditions.  6 satellites is enough to fly, but it won't be a very good lock.


      Regarding the battery life, the first thing you should do is set up the batter failsafe to 3.5v/cell, 14 volts in your case.  Instructions for that can be found here  That will keep you from crashing due to a dead battery.  If you hit the failsafe limit, you can instruct the copter to land or return to launch and land.  You don’t want to run your batteries much below 3.5v/cell.  


      Regarding the 10C number on your battery – that just refers to the maximum discharge rate for the battery.  The mah rating of your battery is considered 1C.  So 1C for your battery is 10 amps (10000 ma) which is also considered the maximum charge rate.  A 10C battery could be discharged at 100amps but would only last 1/10th of an hour or 6 minutes.


      To calculate the estimated flight time, you need to know what your hover current is.  Let’s say it is 20 amps (20000 mah).  You should only plan on using 80% of your battery capacity during a flight.  That’s connected to the fail safe voltage.  So for your battery, 80% of 10000 mah is 8000 mah of usable capacity.  To get the estimate of hover time, just divide your usable capacity by the demand and your result is in hours (8000/20000 = 0.4).  Multiply that by 60 to get minutes (0.4 X 60 = 24 minutes).  Your actual flying time will be less than that because you burn more power when doing maneuvers.   


      The other way you can do this calculation is to use a smart charger if you have one.  Start with a fully charged battery.  Then fly your copter for say 10 minutes.  Put the battery back on the charger and read the mah that it took to recharge the battery.  Let say it took 4000 mah to recharge from a 10 minute flight.  Then your 8000 mah of usable capacity would give you 20 minutes of total flying time.  This is actually the best way to come up with flying time since it uses data from a real flight and not just hovering. 





      Battery Failsafe — Copter documentation
  • hey @darius , i have the exact same board like urs and it runs with NEO 6M GPS (made in china), you did your set-up without touching any PIDs and etc just the setup? what i mean was (freshly Out of box)

    how was the GPS works to you? how many satellite did you receive?

    let me know if everything went smooth.

    best regards!

    • Hi Muhammad, yes I was able to setup my GPS straight out of the box I get 9 satellites inside my house somehow. I never had a problem the GPS. Just the APM, which I finally got right.

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