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Near Fly Away

Discussion in 'Pro/Adv Discussion' started by sesco-lb, Sep 26, 2015.

  1. sesco-lb

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    Okay, so I got my P3P 1 week ago, and did about 15 flights till now, and been very impressed how much it is stable and easy to fly. Going back in time, before I even buy it, I read nearly all the posts in this forum, all instructions and bad experiences the users had with their bird. Back to subject so I reached my flying zone on a top of a hill, where around 800m far, I can see high voltage poles. Here's the best part, knowing that I recommended not to fly around these things, I thought am far from danger, so I turned my phantom on, calibrated compass first time with an error(near magnetic field), I thought because of the car near by and the phones, so I walked couple of meters away, re calibrated the compass and another failure poped on the screen for an instant and then it gave me (safe to fly), long story too short, so I took off, got about 200 m away, and suddenly it started drifting away in unknown direction out of control with a compass error blinking on the screen, heart beats exploded, I though I lost it, but thanks to this forum I quickly switched it to atti mode with zero experience for this mode, and took me about complete 5 mins to get back going left - right - forward and backward against about 12km/hr wind, and catched it with my hands. I NEVER EVER THOUGHT THAT THE POLES CAN AFFECT THE BIRD FROM THIS DISTANCE. I will be spending many and many hours on the atti mode for sure.
     
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  2. Oso

    Oso

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    Wow. You were seriously lucky. You took off with a known compass issue that forced ATTI mode with no prior practice, but you still controlled it and didn't slice your fingers or worse while catching it by hand in ATTI mode for the first time in windy conditions. Really, wow. Super lucky.

    Outstanding idea to spend many hours practicing ATTI mode. It's an outstanding idea for everyone!
     
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  3. StumbleBee

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    The OP should buy a lottery ticket ASAP. His luck will never be better than it is now. :)
     
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  4. sesco-lb

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    But the question am still doubtful about it, is it because of those power lines, or it is just a random compass error?!!!!!
     
  5. StevenQX

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    Maybe there was iron below your feet and you didn't know.
     
  6. sesco-lb

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    No I took off an asphalt balanced side road to the hill, with no issues and stable for the first 200 meters, nothing around me could interfere except for those power poles!
     
  7. Dronason

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    Good you were able to recover it. Same happened to me 2 times. First time I didn't know the ATTI tip, and it finished up-side down.
    If there is too much metallic stuff around when you calibrate the P3 compass, including bellow ground (pipes, reinforced concrete, ...), maybe the P3 accept the calibration and to fly, but when you go up in the air, it is no more affected by all these metallic parts and the calibration then becomes invalid and it starts to drift away.
    You can check in the sensor data what is the MOD value for the compass. It should be around 1500. Also the gyroscope MOD should be 0.00 and acceleration MOD 1.00. For these 2 it is IMU calibration at home that would be required if not ok.
    Having a look on these values is good to have in your pre-flight check list.
    Bellow is a bad sample at my home, so the compass MOD is not good.
    Screenshot_2015-09-19-11-08-47.png
    Best is to have a good calibration of compass in a really remote area with nothing around 100 meters and then to stick to it in general. If you change your flight place for some long distance, there could be change in the magnetic deviation of magnetic North and that would require a recalibration. Also firmware upgrades usually are followed by recalibration, just to be on safe side.
    Sometimes the P3 indicate a compass error at start due to some metalic part in the soil or in the environment. So moving it a little usually do the trick. When it is up, it again get better condition.

    Another think to check is the level of solar activity that can affect the bird. You can check at UAV Weather Forecast the Kp level for a given place and date that could indicate period where it is better not to fly. There are also apps for that.
     
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  8. brianb87

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    Did the app tell you to calibrate? I was just flying close to power lines, shooting a buddies party. I did not calibrate. My mod values were a little high, not by much.
     
  9. StevenQX

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    Have you checked the compass mod value with the bird on the asphalt after your calibration? If not, is this the problem.
     
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  10. sesco-lb

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    Thanks for the info, I'll keep in mind
     
  11. sesco-lb

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    Yes the app asked me to calibrate, 2 times.
     
  12. sesco-lb

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    So what's the correct mod values, do I have to check before each flight ?
     
  13. StevenQX

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    1500 +- 30~
     
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  14. Wibble

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    Well done getting it home safe. Quite an achievement for a beginner!!!
    There is no need to calibrate each flight. Just calibrate somewhere well away from ANYTHING. I even take my watch off!
    I have only calibrated once since owning my P3. I am careful not to place near speakers etc in the car and I make sure I have no errors before takeoff.
    I often fly near powerlines with no problems - I would never calibrate near them!
     
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  15. Dronason

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    That can vary from place to place depending where you leave but I have read for values between 1450 and 1550 are typical.
    What I personally do is that I check these values one time for the first flight for a given place. Now I am more afraid about what is in the underground. After take off, I lift it up at 5-10 meters and hover for some seconds to check its behavior. If it looks strange, then better to land with the finger on ATTI switch and recheck.
     
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  16. Meta4

    Meta4 Moderator
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    You would have to be very close to the powerlines and towers for them to have any effect.
    You didn't mention a distance but I'm guessing you were more than 50 metres from them.
    If that is right, they had no effect at all and your compass error probably if from underground.
    Get a good compass calibration somewhere safe and stick with it.
    Calibrating in an area of distorted magnetic field will cause your Phantom to fly weirdly when you get up out of the distorted field.
     
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  17. Shammyh

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    This.

    Obviously something else was causing a bad compass calibration, either in the ground, or on your person, and this almost certainly lead to the eventual "fly away" behavior.

    Even very high voltage power lines are unlikely to generate a noticeable magnetic field (at least, as compared to the Earth's magnetic field), unless you are very very close to them. The effect of EM fields dissipates exponentially with distance (generally and non-scientifically speaking). Aka, a 2 step move away in distance is a 4 step decrease in EM intensity, if you'll indulge my made up units and a simple inverse-square relationship.

    We all know that change happens rapidly when exponential factors are involved, meaning, you don't have to go far away from a very strong EM field (the powerlines) to no longer be affected by them. One of my favorite walking spots happens to be accessed via crossing a utility easement. This easement has 480 kv power lines. I've walked directly underneath them with my phone compass app on and there wasn't even the slightest glitch. I was actually disappointed to be honest, but turns out, those laws of physics really do apply everywhere...
     
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  18. John Locke

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    What I've noticed is high tension lines will mess with GPS signal reception quite a bit when near them. I can't get GPS signals hardly at all when near them, I need to be at least 150'away, so I try to always be 200' away when flying at one of my nearby flying spots in a park.
     
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  19. Buckaye

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    Yes... I think there was something running under the asphalt that caused this issue... I get compass errors on my deck if I place the Phantom right over the screws... My guess is there was something hidden underground that caused your issue... Meta4 I think has the right idea....
     
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  20. N017RW

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    The effect is most likely due to the low cost implementaion of the GPS engine in our Phantoms (i.e. shielding).

    At the risk of digressing a bit from compass to GPS interference issues, here's an interesting research paper if you're interested. It gets pretty deep but the intro and conclusion sections are pretty 'digestable' IMO.

    Just bypass the need to sign-up,login, etc. It worked for me.

    Investigating the Impact of High Voltage Power Lines on GPS Signal | Ahmed Hattab - Academia.edu
     
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