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Why won't my Compass Calibrate??

Discussion in 'Inspire 1 Discussion' started by John Casey, Aug 24, 2015.

  1. John Casey

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    I tried to fly today-out of town in a paddock - no power lines no trees - just open land and blue skies and sunshine. But when i tried to calibrate the compass, I just coninued to get a warning stating that there was a compass error, and I should switch P-GPS off. When I checked the sensors, they were quite low (1300-1390). I did it about 30 times, and only twice did the sensors readings look OK (about 1500). I did take off but only hovered about 2 metres above the ground and moved around a bit but onlt a metre or two. The aircraft appeared to have a bit of difficulty flying in a straight line. I ran the battery down to about 30% and landed. i then tried another battery, but the same thing happened. I checked the IMU and it said the IMU calibration was OK. Does anyone have any clues as to how I can get a good quick calibration?
     
  2. Aviator

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    Check your pockets for metallic and/or magnetic devices/gadgets (mobile phones etc..).
     
  3. Kilrah

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    And make sure you're not on a metallic structure.
     
  4. The Editor

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    Do your calibration at home (or wherever you know you get a good calibration) and leave it alone.
    There was obviously something affecting the magnetic field at the location that was unseen (probably beneath your feet). If you had calibrated there and continued to fly I wouldn't mind betting you would have experienced TBE or worse, lost control of your AC under P-GPS mode.
    This is why I always advise NOT to calibrate out at location - for the very reason you experienced.
     
  5. John Casey

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    This confuses me immensely. I have seen you write this on many occasions, and I respect your wealth of knowledge but I cannot understand how one can calibrate in one place and not re-calibrate before taking off again, when I have had nothing but trouble with drifting calibrations. For example, my worst moments of owning an Inspire 1 when I landed for a battery change, changed the battery and then took off again and the aircraft went crazy. I did manage to land it and I immediately checked the sensors, and they had shifted from 1500 to 1300 on that battery change. I did another calibration and the readings went up to 1500, and I took off again, and it flew normally. So I just can't see how I can get away with not calibrating before every take-off. But this one would not work at all.
     
    #5 John Casey, Aug 24, 2015
    Last edited: Aug 24, 2015
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  6. John Casey

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    No I'm out in the Australian bush. Nothing for many miles except land and sky. I had 17 sattelites visible, and it was mid afternoon on a bright sunny day. the only object there was my car about 10 metres away.
     
  7. John Casey

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    No nothing in my pockets. Phone is in the car 10 metres away. And 2 different people tried the calibration.
     
  8. Kilrah

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    Looks like your bird is defective then.
     
  9. LockMD

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    Or a big metal object is buried under your feet ????
     
  10. John Casey

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    Or perhaps I should try to understand what you are saying, because it doesn't make any sense to me. Are you saying that I should calibrate at home, then drive 80 kms and just fly ? Without calibrating again on location? Should I check the sensors readout and if they read low or high, should I then ignore them and just fly? Or if they are reading something other than 1500, should I then re-calibrate? If the App says to re-calibrate, do I ignore it because I've calibrated at home before I left. And under what circumstances should I decide to do a compass calbration? I'm not trying to be smart or disrespectful here, but it just doesn't make sense to me, and is totally opposite to all other advice I've received, and experienced.
     
  11. John Casey

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    What part, the compass? Any idea what the remedy is?
     
  12. John Casey

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    Well, not real likely considering it is Australian pristine bushland and nothing around for many kilometres. And I have been there months before and did a calibraton in that spot some months before.
     
  13. The Editor

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    But you do not know what was underground immediately under your feet!
    Iron ore, magnatite rocks etc
     
  14. Aviator

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  15. The Editor

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    Yes.
    Yes - ALWAYS check your mod values before you take off.
    No, if they are out of range - Move, your compass is being thrown out by some local magnetic influence.

    No - your compass is being thrown out and is not accounting for just the magnetic declination at that location - move several feet and check the readings again.

    I actually cannot remember the last time I did a compass calibration other than when a new firmware is released (not counting beta versions etc).
    I have travelled 100's of miles between flights (over 250 miles in a couple of instances) and never recalibrated.
    I NEVER take off if any mod values are not within tolerance.
     
  16. John Casey

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    OK- Fair enough. But When I was flying a couple of months ago and had troubles, I did a compass calibration on the side of the road, flew for 18 minutes, ran the battery, landed on the spot I took off from, replaced the battery, took off again and it was almost out of control. I managed to land it again (soft normal landing) and checked the sensors readouts and they had dropped from 1500 to 1300. I then re-calibrated and they went back to 1500 so I decided to take off again to check if it was now OK, and it was perfect. Do you have any idea why that would happen? Because that is why I am too scared to omit to do a calibration. I suppose I could have just checked the sensors, but it still would have required a re-calibration on the same spot 20 minutes after the first one (which was OK). The only thing is that it was within 3 km. of where I was yesterday, so I guess it could be the area itself but it would have to be naturally occurring because there is nothing there except mountains and paddocks and creeks etc.
     
  17. John Casey

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    No I have no idea what the geology of the area is made up of. It is a rural area.
     
  18. John Casey

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    I did move about 200 metres up the road and try again, but not much better, although I did eventually get it to calibrate.