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Compass Error

Discussion in 'Inspire 1 Discussion' started by David Pelly, Mar 1, 2016.

  1. David Pelly

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    Hi Guys,

    I was out flying yesterday evening at a site I have flown at many times before with no problems. After completing all the usual pre-flight checks I embarked on my first flight which lasted around 14 minutes with no problems. My second flight was somewhat different, after hovering for about 30 seconds to check everything and make sure battery was up to temp ( air temperature was 4 degrees C and I had preheated the battery with the DJI heater). I then proceeded with the flight and 30 seconds into it when I was about 40m height and 150m distance I got a compass error suddenly come up on the Go app and the Inspire started to do its own thing with no input from me. I immediately switched to ATTI mode and got control of the aircraft and got it back home and successfully landed it. I then did a full compass calibration and then completed 3 further flights with no problems at all.

    Anybody got any ideas what could cause this? I do not routinely do a compass calibration every time I fly as recommended by the Editor. The site where I am flying is open countryside over moorland. There are no overhead power lines or underground cables present anywhere and I always have at least 17 satellites showing on my display.

    Cheers

    Dave
     
  2. The Editor

    The Editor Moderator
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    Very difficult to say what caused it other than if possibly your previous compass calibration was on the 'threshold' of being a good one.
    Even then, being over 100ft up should preclude anything on or under the ground from affecting the magnetic flux acting on the compass. Are you are confident your mod values were all fine prior to take off (specifically compass)?
     
  3. David Pelly

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    Thanks for your input Ed. All mod values and compass readings were fine before take off and the 30 second hover was rock solid. It just had the compass error flash up suddenly and everything went haywire until I took control in ATTI mode. Had I not switched to ATTI I think this would have been a fly away/ lost quad thread !

    As I say I fly very regularly here and have never had any problems. Just shows that you should always be aware that even with good pre flight preparations things can go wrong very quickly
     
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  4. The Editor

    The Editor Moderator
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    Very true.
    I would have to put this one down to a software glitch although I REALLY hate not knowing the cause of something.
    Glad you caught it quickly which is why I drum home to people always be competent and ready to switch to Atti if necessary. :)
     
  5. David Pelly

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    Been thinking real hard about this one.
    The site I fly at is overlooked by a hill on top of which is a transmitting mast which does local TV and mobile phones. I've flown at this site with rc aircraft and helicopters for years and in the old days of 35mhz we used experience the odd glitch always in the same particular area which we put down to the mast. Since the change to 2.4ghz we have not experienced any problems. We have also been flying Phantoms and Inspires here for 2 years without any problems.
    Could the transmissions from the mast cause an upset in compass calibration whilst in flight? I would think the mast is about 1.5 km away from us.
     
  6. The Editor

    The Editor Moderator
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    Not really - You can possibly get caught in the Fresnel focal area of a microwave link which can blow out 2.4ghz connection. However, compass would be unaffected and even if you lost your control link the Inspire would just hover for a few seconds, then realise it has lost command link and then initiate RTH.
    A cell tower transmission or microwave link would not alter the magnetic flux acting on the compass and certainly would have no affect from over a kilometer away.
    Still a mystery.......
     
  7. David Pelly

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    Thanks ED.

    I think it must be down to a software glitch as you originally suggested. Like you I hate when it you can't put your finger on exactly what the problem is.
     
  8. The Editor

    The Editor Moderator
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    Yup - hate not knowing. :mad:

    You have already completed a compass calibration since the incident and that maybe all that was required to rectify things. I would just keep a lookout for it again but would imagine you will not experience another occurrence.