Crash on maiden flight- need help

Well, I should have taken the advice of, pretty much everybody, and built a simpler model as my first build. But I didn't... I jumped right in and built a DYS D800 X8, and a Tarot X6 at the same time. I took the D800 X8 out yesterday for her maiden flight.

I really took my time building this thing. I studied everything I could find. I used a Pixhawk, and I very carefully did all of the calibrations, and motor checks in Mission Planner. From my limited experience, it all looked good. Motor numbers, and rotations all look good. I was very careful about installing the props. I'm pretty sure I got all that right.

Here's what happened: I found a great place to maiden flight. Set up everything. radio on. Battery on craft connected. Tower as a GCS. Everything looks good. Good GPS. I armed the craft, and got very nervous, so I disarmed. Did that about 7 times. Finally got up the nerve to go for it. Throttled up, and she rose a bit and immediately did a very fast back filp to the port side and landed about 10 feet away. Some damage, but it can be repaired.

Now I'm trying to figure out what went wrong. I'm a beginner at all this, and reading flight logs. At first glance it looks as though the voltage drops out, and the current spikes as soon as I throttle up. After adding a few more lines to the chart, it looks as though the barometer is going crazy each time I armed/disarmed (when the props spin). The barometer really went crazy on the fateful throttle up.

Could one of you kind folks please take a look at my flight log to help me determine what went wrong and how to fix it? I'm a beginner who took on way too much. However, I am a quick learner. I just need some help. I have attached the log. Any help would be greatly appreciated!

2017-01-18 12-28-14.log

2017-01-18 12-28-14.bin

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  • hello, do you still have this drone? can I buy your tarot x6? its sold out every where!
  • Well I hooked up a power analyzer and took off (with a 7 lb. payload in addition to the craft, for a total AUW of about 12 pounds) with these "max" results:
    1517 Watts Peak
    6.6 Watt Hours
    1143 Amps Peak
    445 Amp hours

    ...but I don't know how to interpret these in terms of (1) am I ruining the battery or engines? (2) does it tell me why the flight times are so short?, and (3) is it telling me anything about whether or not the batteries in fact did have 16,000 Amps.

    Interpretations and other suggestions welcome.
  • Thanks for the reply.

    Flight time with no “additional payload” is about 8 minutes, with the red-blinking light on almost from the first 10 seconds.
    Do you think the 10C discharge rate is an issue?  I suppose not, because while it might reflect a strain on the set-up to fly, it would not explain the short flight time.
    I re-tuned my scalp and I think I get what you get (image attached).
    This DIY drone guy is looking again at just buying a DJI Spreading Wings 1000 configuration... I almost give up.
    -Peter

    ecalc screen shot.png

  • I would be careful discharging your batteries to the point where it won't take off - this will almost certainly damage them.

    I just configured your setup in ecalc and it's coming back with a hover flight time of 8.9 minutes.with an AUW of 12 lbs. Mixed flight time is only 6 minutes, so realistically you're pushing the limits of this setup with that much weight and a better battery isn't going to help all that much

    What's your flight time with no payload attached?

  • Well, flew just now and one flight (WITH full load of 12 lbs AUW) lasted just 3 minutes and the other about just 2 minutes before the drone landed itself.  Not good.  The red blinking warning light came on almost immediately on take-off.  

    -Will now recharge at least one battery, then attach the power analyzer and look at the results after increasing throttle take-off power.

    Delete me Feb 28th.png

  • Dear Justin,

    Thanks for the continued assistance here.  

    First, to your points:  Yes, the voltage shows 16.8 when fully charged.   I can't figure any way to test the mAh inside (maybe don't know my multimeter well).  I have not attached a power analyzer, but I will today.

    The low voltage levels to on my flight controller are set to 13 volts, if I recall correctly.  It's a Naza M Lite.

    When I flew yesterday, a fully-charged battery lasted only 8.5 minutes before no amount of "pitch" would keep it aloft, and it settled to the ground.   Tried it again with another battery and got about the same result.

    I recharged the batteries after being sure remove the "capacity shut-off" and one took 2.5 hrs. to charge on a 5 Amp charger, and the other took a whopping 5.5 hours to charge on a different 6 Amp charger.     So "hope springeth eternal" that it might have been a charger issue.

  • I think it fairly unlikely to be a problem with the batteries or the charger, more likely something to do with the set up of your X8.

    Have you measured the battery voltage with a lipo tester / multimeter? (should be 16.8V when full for a 4s battery)

    Additionally, what have you set the low voltage levels to on your flight controller? You've not mentioned which one you have other than it being DJI.

  • Ah.. second correction on my part.  I was measuring some "spares" in a kit bag.   The actual ones on the x8 are, as you suggest they should be, 12".  

    And the mounting on the X8 is as follows:   All 4 on the top rotate CCW and all four on the bottom rotate CW.  Seems wrong to mount the bottom ones "upside down", but that is what I have to do to get the lettering on top.

    Thanks for the response.   Do you think the nearly instant re-blinking light is from the lack of mAh in the battery?   Any way to test how much mAh it contains (to see if the charger is the fault)?

    -Peter

  • Ecalc probably isn't far off saying it won't get off the ground, those props are WAY too small. Those motors are designed to be used with 11-13" props on 4s. (and would need at least 30A escs.)

    http://www.rctigermotor.com/html/2013/Professional_0912/46.html

    I'd suggest you find some carbon 12" or 13" props (if they will fit your frame)

    Peter Farnsworth said:

    Thanks.  

    First a correction on my part:  the battery is a Multistar 14.8 volt 16000 10c   

    Other details: 8 motors are T-Motor MT2814  KV 770   the props are 8" APC ones with a 4.5 pitch  The payload, including batteries, etc. (AUW?) is 10 lbs.  (5400 grams)   The frame is 24" square.  

    (I tried eCalc and it says the x8 won't get off the ground, so I must be inputting something wrong there).

    Someone suggested my charger is blocking the full mAh, so I loaded my own settings and charged it.  We'll see if that works as soon as I can get back out to fly it.

  • Thanks.  

    First a correction on my part:  the battery is a Multistar 14.8 volt 16000 10c   

    Other details: 8 motors are T-Motor MT2814  KV 770   the props are 8" APC ones with a 4.5 pitch  The payload, including batteries, etc. (AUW?) is 10 lbs.  (5400 grams)   The frame is 24" square.  

    (I tried eCalc and it says the x8 won't get off the ground, so I must be inputting something wrong there).

    Someone suggested my charger is blocking the full mAh, so I loaded my own settings and charged it.  We'll see if that works as soon as I can get back out to fly it.

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