Welcome to PhantomPilots.com

Sign up for a weekly email of the latest drone news & information

What just happened to my P3P?

Discussion in 'Pro/Adv Discussion' started by Reuben, Aug 25, 2015.

  1. Reuben

    Joined:
    Jun 14, 2015
    Messages:
    53
    Likes Received:
    6
    Guys I might be playing a bit dumb here but just wanted to know if anyone had any similar behaviours.

    So today I decided to go fly my p3p over a marina at night to take some cool shoots of the light colours at night with reflections on the sea and here's what happened.

    Firstly I live in the UK and currently on holiday in Malta with my p3p since I arrived in malta I only did one compass calibration which was before my first flight In Malta due to the large distance in miles from the UK.
    After that never got compass error so just flew it freely with no problems until today.

    I started up the bird while I was on top of a parking lot adjacent to the marina and first thing I see was gimbal over load and compass error. So restart the bird and gimbal overload was gone but compass error remained I checked the sensor values and they were around 12000 so thought it would be wise to recalibrate. So went ahead and tried to do the calibration and no success. After 5 attempts I gave up and moved to right adjacent to the marina on the ground floor outside of the parking lot. The reason I did this cause I thought that one of the reasons the compass is messing about was due to the wire mesh that was probably inside the concrete below me and also the parking lot lights and electricity below me.

    Anyway after moving right next to the marina same thing compass error and calibration failed but after the 2nd failed calibration attempt the compass error disappeared so I checked the sensor values and they were just above 14000 so thought it was safe to fly even though the compass failed to calibrate. (Silly me I guess) anyway I told to my self be very careful as something is not right. And something in my head was telling me pack it up and go home and don't fly. Anyway took it up in the air about 3 meters and let it hover first as I always do but 2 seconds into the hover this bird started drifting all over the place backwards forwards left right completely crazy also I got compass error again in the air. I missed the parking lot wall by inches at one point. Luckily enough I managed to descend it down and land it safely without a scratch. And believe me it wasn't easy as I had a parking lot behind me. Road lights on poles in front of me and open sea with the marina in front of me. Not to mention the people that gathered around to watchful bird fly. Lol I felt like a complete fool. After landing I decided I would not fly it again there but still wanted to check if I could calibrate the compass successfully after another 3 attempts it was finally successful but still packed it up and went home.

    So my question is does the compass have anything to do with keeping the bird in a stable position? Shouldn't the GPS take care of that? Excuse my ignorance if that question is to dumb. I'm here to learn!! Also do you guys calibrate compass before every flight? Because from what I read here compass recalibration is only needed if you travel over 50 miles from previous flight but DJI recommends a calibration prior to each flight so which is the best practise? Tomorrow I can load up the flight logs from the controller and aircraft if that helps provide further investigation.

    My last questions is can anything be done if you want to fly in an area with strong electromagnetic interference so I can fly the bird safely?
     
  2. bobmyers

    Joined:
    May 10, 2015
    Messages:
    3,611
    Likes Received:
    866
    Location:
    San Antonio, TX
    You compass errors were due to metal or strong magnetic interference. Steel in concrete, steel frames, chain link fences-- if it is metal and close to your Phantom, it may cause a compass error. This is especially bad when you take off-- the Phantom may do unexpected things as yours did. Calibration will not solve a compass error-- only moving to a different location which is away from the metal.

    No, you do not need to calibrate the compass after every flight.

    No, you shouldn't fly in an area of strong electromagnetic interference-- it is just too risky.

    So what version of FW are you flying, which tablet, and which app?
     
    clkilljoy likes this.
  3. Oso

    Oso

    Joined:
    May 19, 2015
    Messages:
    2,536
    Likes Received:
    1,483
    Location:
    Sacramento CA
    Am I reading this correctly? You lifted off with a compass mod value of 14000? If so, you are very lucky things weren't much worse!

    I would have tried to calibrate the compass a kilometer or two away (nearest open field) and then gone back to the marina to try flying without recalibrating.
     
    #3 Oso, Aug 25, 2015
    Last edited: Aug 25, 2015
  4. JohnK

    Joined:
    Jun 4, 2015
    Messages:
    512
    Likes Received:
    169
    Location:
    Hudson Valley, New York
    Yikes. Based on all the things I've read, checking the mod is now part of my pre-flight checklist, and since I can't rely on my flagging memory these days, I have a big card glued into my carry case to remind me of the essential pre-flight steps. Wouldn't have known to do that without this site, so credit to all of you who provide new people with good info and tips.
     
  5. Meta4

    Meta4 Moderator
    Staff Member

    Joined:
    Jan 8, 2014
    Messages:
    7,750
    Likes Received:
    3,462
    The Phantom has lots more sensors beside compass and GPS.
    It uses a combination to maintain position.
    The compass is essential for flying straight.
    The manual does not say to recalibrate each flight. It mentions calibrating for each new location .. but they don't define new location.
    Experience and DJI support guys have confirmed that if you are within 100 miles of home recalibration isn't necessary.
    (I was 500 miles from home last week and couldn't find a good location for calibrating and flew 16 flights safely without recalibrating).
    As you've found out the risk of flying with a bad calibration is high.
    There are very few flying locations where strong electromagnetic interference will be encountered.
    It's really hard to give an answer because there are so many variables.
    What you guess may be strong electromagnetic interference may not really be strong or might be imagined.
     
  6. Reuben

    Joined:
    Jun 14, 2015
    Messages:
    53
    Likes Received:
    6
    I was running 1.2.6 FW and the latest Go App on iOS iPad mini 2
     
  7. D4T_PoM

    Joined:
    Jul 28, 2015
    Messages:
    693
    Likes Received:
    183
    Location:
    London UK
    Agree, you have to understand that if your on top of a car park the materials inside the concrete were you stand, its mostly iron and steel.

    I usually fly from my driveway but when I tried to take off a few feet away from the street corner where there was bollards I got a compass error and realised it was due to the bollards, moved away and it was fine, I tried taking off in the park not far away from a bench and it gave me an error because of the material the bench was made from lol.

    Always be safe and check surrounding for possible interferance.
     
  8. jonnylees88

    Joined:
    Jun 20, 2015
    Messages:
    62
    Likes Received:
    15
    What is checking the mod john ?
     
    StumbleBee likes this.
  9. bobmyers

    Joined:
    May 10, 2015
    Messages:
    3,611
    Likes Received:
    866
    Location:
    San Antonio, TX
    That is probably one of the issues-- if you are running the DJI Go app and IOC on 1.2.6-- that will create some issues within itself. When DJI released that app update, and your IOS device installed it-- it may have updated your controller with 1.3.2-- which demands that the aircraft be updated also. I had some major connection issues with mine for the same reasons. May not be the cause of your issues -- but the GO app will create connection issues, especially when the controller and aircraft have two different FW versions.
     
    Fplvert likes this.
  10. JohnK

    Joined:
    Jun 4, 2015
    Messages:
    512
    Likes Received:
    169
    Location:
    Hudson Valley, New York
    DJI indicates that if your compass MOD value is lower than 750 or greater than 2250, you should recalibrate the compass. You can check it in the Sensors menu, which you will see when you click the icon next to the home icon in the upper left corner of the GO app.

    I check mine after the lady voice tells me that home point has been recorded.
     
    #10 JohnK, Aug 26, 2015
    Last edited: Aug 26, 2015
    unclejas likes this.
  11. AlphaZeroOne

    Joined:
    Feb 11, 2015
    Messages:
    39
    Likes Received:
    5
    Interesting post. I'm left wondering also, as you were in or near a marina, how many of those moored boats had their GPS and navigation equipment switched on. Just a thought but it is well known that wifi and other electronic equipment can become problematic to anyone flying near or through the vicinity.
     
  12. MattyDread

    Joined:
    Jun 23, 2015
    Messages:
    328
    Likes Received:
    108
    Location:
    Canberra - Australia

    I thought the mod value should be be closer to 1500 - between 1450 & 1550 otherwise I'm not pushing that stick up !:)
     
  13. JohnK

    Joined:
    Jun 4, 2015
    Messages:
    512
    Likes Received:
    169
    Location:
    Hudson Valley, New York
    Yes, but DJI apparently uses 750-2250 as the extreme range. 1500 is the midpoint of this range. Most of the posts I've read have therefore strongly recommended around 1500 as the "Sweet spot". I am not expert on this - just the result of reading LOTS of posts when I had a minor back injury.

    I'm with you on the 1500 number - I want to be one of those people who never experiences a flyaway. Apparently, they exist ....
     
    #13 JohnK, Aug 26, 2015
    Last edited: Aug 26, 2015
    P3ChinaSkies likes this.
  14. Oso

    Oso

    Joined:
    May 19, 2015
    Messages:
    2,536
    Likes Received:
    1,483
    Location:
    Sacramento CA
    Gyroscope Mod should be around 0.00
    Acceleration Mod should be around 1.00
    Compass Mod 1400-1600
     
  15. P3ChinaSkies

    Joined:
    Aug 25, 2015
    Messages:
    62
    Likes Received:
    10
    Best advice I've heard today JohnK. And you made it simple. Check it after the Lady sings.....
     
  16. JohnK

    Joined:
    Jun 4, 2015
    Messages:
    512
    Likes Received:
    169
    Location:
    Hudson Valley, New York
    Thanks!!!
     
  17. Reuben

    Joined:
    Jun 14, 2015
    Messages:
    53
    Likes Received:
    6
    i did think that also actually. on more thing i thought about is that all the moored boats have a 3 phase electricity connection so that must have created some serious interference also
     
  18. Reuben

    Joined:
    Jun 14, 2015
    Messages:
    53
    Likes Received:
    6
    sorry I meant to say just above 1400. must have typed in an extra "0" :) i always make sure I am between 1400and 1600 before takeoff. checking the mods is in my preflight checks always!!!
     
    Oso likes this.
  19. Reuben

    Joined:
    Jun 14, 2015
    Messages:
    53
    Likes Received:
    6
    but the bottom line seems to be that the compass mod is not everything. even though i was just above 1400 the bird still acted crazy
     
  20. Reuben

    Joined:
    Jun 14, 2015
    Messages:
    53
    Likes Received:
    6
    for those interested here is the logfile from my ipad. you can see the drone moving laterally without any stick inputs. the only inputs i made was to avoid the wall behind me and eventually to land it.
     

    Attached Files: