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A bit of a scarry launch today

Discussion in 'Inspire 1 Discussion' started by JimPA, May 11, 2015.

  1. JimPA

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    I took the Inspire out for an early morning flight this morning to get the sunrise at Lake Erie near where I live. I'm guessing I've had about 80+ flights at this point, so not my first time.

    I was launching from a pier that was mostly concrete. It had metal sides and when I was near the one side of the pier I got a compass warning. So, I moved to the center of the pier and the error went away. Had good GPS lock and the safe to fly status. I used the auto launch and soon as she got off the ground she started to drift pretty good. I was not too far from some small trees, so I decided to get some height. It kind of was doing what it used to do a few firmware updates ago where it would do the whole circling the drain, but this time the drain was like 30-50ft wide. I had to put a ton of stick into it to offset what the Inspire was doing on it's own.

    Once I got up to about 50 ft it all cleared up and the rest of the 10-13 minute flight was uneventful. I did not get near or try to land on the pier. I landed in a nearby parking lot and had no other issues. I launched two more times from that same parking lot.

    I did not look at my MOD values, but will from now on. I don't think this has anything to do with the latest firmware. I'm sure it had everything to do from launching from an area that had too much metal in it.

    This is more of a warning or note to other's not to do this. I got lucky and was able to get it under control.
     
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  2. jon b

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    Yep, seen the same kind of thing happen flying not just the Inspire. The compasses are pretty sensitive.
     
  3. The Editor

    The Editor Moderator
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    I'm sure that HAD you have checked your mod values (as you should do before EVERY launch) they would have been outside of the acceptable range.
    This is why I advocate NOT compass calibrating in the field/launch site. Had you have calibrated on the pier this compass mod values would have adjusted for the Inspires immediate environment (the pier). Then, once you were airborne the influence of whatever was in the pier would be absent and you would have a skewed compass calibration and quite possibly crashed.
    You said yourself, once you were clear of the Pier everything behaved normally. Had you have calibrated on that pier I would guess that would not have been the case!
    Glad it worked out and .........check those mod values EVERYTIME
     
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  4. kenny kustom

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    So, where should the calibration be done ?
    if he had checked his mod values, and saw them out of line, what should be done ?
    find a different launch site ? ( not being a smarty pants.. just trying to understand more )

    BTW.. the on hold music for dji is really bad.....
     
  5. The Editor

    The Editor Moderator
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    IMU should be done on a flat level surface with no outside disturbances or vibrations
    Compass calibration should be done in an area away from magnetic interference (I use the same spot in my garden I have used form years)
    If compass values are abnormal then yes, do not take off from that spot.
    You have the last say whether you go airborne or not..... If something isn't right then do not fly. The pilot ALWAYS has the last word.
     
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  6. m00se

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    i made about 30 or more flights from an area that was absolutely tiny, and had magnetic interference all around it. if i moved the i1 more than 30cm in any direction i got the light sequence showing the compass had to be calibrated.

    i took off quick each time to get up and out of any possible trouble, and landed quickly, but i only ever got any degree of compass toilet bowl dance once.
     
  7. JimPA

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    An update to my earlier post about a bad launch I had.

    I went back to the same pier and same location and checked the MOD values. While near the side of the pier where I got the error I was reading 2200. When I moved closer to the center I was still reading values between 1750 and 1900. So, I'm pretty sure this is my reason for my erratic flight. On the walkway to the pier, there was a metal plate. Just for the heck of it I put the AC on that and read 3300.

    As a side note....In the parking lot were I launched from several times, while on the sidewalk where I was setting up I got readings 1700-1800. I'm guessing there is some rebar in the concrete. Over in the middle of the asphalt parking lot I was getting mid 1500's.

    Moral of the story....ALWAYS check your MOD values prior to launch.
     
    #7 JimPA, May 13, 2015
    Last edited: May 13, 2015
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  8. White Airwolf

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    And what should the MOD values say then?
     
  9. TR1PL3D

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    From reading various posts on various forums, the below seems to be the target IMU values.

    GOOD IMU VALUES:
    GYRO= 0
    ACCEL= .99-1.01
    COMPASS= 1400-1600
     
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  10. Drone Mastery

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    I have 92 flights, Never had any flight issue, I ALWAYS calibrate compass before first flight of new location then check mod values. You can't over-calibrate your compass, if the values are bad where you calibrate it then i would find a different location.