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Professional P3P Instability Problems Clarified After 1.2.6 Update

Discussion in 'Phantom 3 Help' started by GadgetGuy, Jun 26, 2015.

  1. GadgetGuy

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    I can now reliably predict, before launch, whether my P3P will launch safely with stability.
    Unfortunately, it isn't happening very often, but this is major progress! No more uncertainty before lift off, and no more pushing the limits of my ATTI and manual flying abilities, trying to immediately safely hand catch the rogue craft before it crashes wildly out of control!

    The key is the displayed Pilot app nose direction on the map. If the Pilot aircraft nose direction on the map is the SAME as the true current aircraft nose direction on the ground, the flight will be stable. If it isn't, it won't be. Don't take off. Keep recalibrating the compass until they agree. Unfortunately, it may only be correct for one out of 5 allegedly "successful" calibrations, and if successful, the successful calibration will usually not even survive a simple battery change! On my Pilot map, whenever the launch will be unstable, the Pilot nose consistently points 70° to the right of the true aircraft nose direction, which means the compass is still off by a full 70° even after a "successful" compass calibration. However, if I keep recalibrating the compass, and turning the aircraft battery off and on, and relaunching the Pilot app, eventually it will be correct, and I can launch with no problems until the aircraft battery is turned off, or replaced with a fresh battery. Then, I have to start all over again, to try and get a proper compass calibration where the Pilot app nose direction agrees with reality, before I can relaunch with the same stability, but I cannot depend upon the Pilot app report of "Normal" for the compass, nor the aircraft confirmation of a successful calibration. Only the nose knows! ;-)

    I have been plagued with these instability problems since the 1.2.6 FW update. As a result of this instability, immediately after one takeoff, I had one minor crash that I could not prevent, which appeared to have only damaged the props, but the issue existed well before that crash. I was able to avoid crashing during the other unstable flights, because the aircraft still remained in sight, but on the one unstable flight that crashed, the craft hooked wildly left upon throttling up, and flew up over the rooftop, and completely out of my line of sight!

    Following the sage wisdom of blade strike, after recalibrating the IMU on a level surface and recalibrating the gimbal and Compass yesterday, the majority of my last 10 post crash test flights have still been unstable, but all were recoverable, thanks to my vigilence!

    However, seemingly randomly, since the Update, I have had several completely normal stable flights. However, each time I have had a safe test flight since the crash Monday, as soon as I replaced the depleted battery used for testing with a fully charged one, to enjoy safely flying my P3P for an extended flight, the instability would immediately return. Then, I started paying attention to the Pilot app nose direction before launching. I got lucky and had a full battery in the craft when I got the Pilot nose direction agreeing with reality. I spread my wings and took off!

    My last successful flight this evening was to a location a full 2,700 feet away and back at a height of 300 feet, covering over a mile with a level horizon in the video (Yeah!). No issues at all during the flight, recorded in 4K video. However, as soon as I turned off the aircraft battery and turned it back on again, the Pilot app once again showed the nose pointing 70° to the right of the true aircraft nose direction, meaning a relaunch would have been unstable again!

    My biggest concern is that the Pilot app and the aircraft are both reporting a Normal compass reading and a correct compass calibration, but can still both be off by 70°, when the Pilot app nose direction doesn't agree with reality on the Pilot map before takeoff. Seems like the compass calibration checks are creating a bogus "Normal" state when things are wildly off! However, they randomly agree with reality, and a safe flight results. I just wish it was more often that they agreed!

    Any thoughts or suggestions?
     
  2. Akrosfer

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    Last week i tried flyind my P3A to a point which is about 6200 m.away from the home point and RC. I could fly it to 5400-5500 m. before losing the signal. Waited silently for a couple of minutes hoping that the "go home" function works properly. When i got the signal again, The Phantom was flying to the home point in correct direction. The only problem was the 20% percentage of the battery about1500m. away from me. The UAV probably drained the battery faster during its auto "Direction true? Yes. Direction true? No. Correct it." style slow fly. So i chose a safe (preselected before flight) place to land the UAV and get it by car.

    Why am i telling these to you?
    After the flight, i checked the flight records and realised that "wrong direction of the nose" problem on the app.for the first time.
    The UAV flew into a direction but the nose looked to another direction on the app. Lucky me, nothing wrong happened during the flight, including the "go home" auto fly part.
     
  3. GadgetGuy

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    Akrosfer, impressive and very interesting. There is one YouTube video in Turkey of a 7,400 meter distance flight and return, and he switched to ATTI mode to get the best speed and battery performance, and still made it back home with 10% battery left. Thinks he could do 8,000 meters next time by flying straighter! These long range flights are best conducted with a chase crew, like hot air balloons require! Best if there is someone at the other end to hand catch it and secure it for you!

    The nose direction issues in 1.2.6 are indeed troubling, and I have also on occasion seen inverted arrows too!
     
    #3 GadgetGuy, Jun 26, 2015
    Last edited: Jun 26, 2015
  4. happydays

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    Great tip. Mine flies faultlessly, but a brief check could save someone else a headache. Just a thought, there aren't any magnetic interference issues in the rocks in the terrain where you are, are there? Probably not, as I suppose they would not have allowed so many compass calibrations to take place. Just a thought.

    I had an issue with my PV+ which took off on its own due to magnetic interference in the area. I now have a cheap compass that i wave around to check the area if I'm unfamiliar with it.
     
  5. Meta4

    Meta4 Moderator
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    I'm wondering if you are going the wrong way on this.
    A problem with the direction showing in your app sounds suspiciously like a calibration problem with your mobile device.
    If this is the problem, any amount of recalibrating the compass in your P3 won't fix it.
    If your Phantom has no problem flying straight it doesn't sound like there's any problem with the Phantom's compass.
    All that recalibration should be unnecessary. Get a good compass calibration and stick with it.
     
    Akrosfer likes this.
  6. FRBEAR

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    Interesting. I flew today with a new battery and had an unstable launch. The first compass cal failed and I repeated the procedure. First launch took off sideways and I landed in the grass. I had 2 successful flights after that. Moved about a 1/4 mile and inserted another battery and even though everything showed OK, it took off and went sideways again. I had left the gimbal lock on when powering up and thought that may have been the problem.
     
  7. GadgetGuy

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    Unfortunately, the few good compass calibrations do not even survive a battery change. It only flies straight if the Pilot nose direction agrees with the actual nose direction. If they don't correspond, it won't hold its position or fly correctly. I only wish I could stick with the good compass calibration. It only lasts as long as the battery power is on.
     
  8. Meta4

    Meta4 Moderator
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    Have you calibrated the compass in your tablet?
     
  9. GadgetGuy

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    I get prompted to roll the ball in the circle that I do, every time I launch the Pilot app. Is that the iOS tablet compass calibration you are referring to? Is there a way to initiate it independently of the app to make sure it is done properly?
     
  10. Meta4

    Meta4 Moderator
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    I'm not familiar with IOS issues or the ball in the circle thing but when the Phantom direction in the app is wrong it's usually an issue with the compass in the tablet. Google may be some help to find an app or a method for calibrating your tablet's compass.
     
  11. GadgetGuy

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    I just re calibrated the compass in my iPhone 6+, using the Compass app (cool app!). It brings up a compass when successful. I don't get that compass at the end when I get prompted to roll the ball in a circle on my iPad Mini Retina by what I assume is the Pilot app. Will look into recalibrating the iPad Mini compass when I get home, and will try using iPhone 6+ instead. I think you may be on to a possible solution!
     
  12. TAZ

    TAZ

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    You are promoted to recalibrate you iOS compass every time you launch the Pilot App? Every time? That isn't normal. I have iPhone 6, and I'm never prompted to recalibrate my phone when I launch the pilot app. Sometimes when I get in my car...but that's normal, as I'm surround by metal.
     
  13. bobmyers

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    FYI-- Here are some notes off the Apple site re compass calibration on IOS

    iPhone and iPad: Calibrating Compass

    You may need to calibrate the compass on your iPad or iPhone 3GS or later before using Maps, Compass, or other apps that use this feature.

    To learn more about Compass, see the user guide.
    [​IMG]

    The built-in digital compass works like a magnetic-needle compass. The accuracy of digital compass headings can be affected by magnetic or other environmental interference, including interference caused by proximity to the magnets contained in the iPhone earbuds. The compass may need to be calibrated from time to time.

    When the device displays the calibration alert, tilt the screen to move the red ball around in a circle. You should use the digital compass for basic navigation assistance, but you shouldn't rely on it to determine precise locations, proximity, distance, or direction.

    When this warning comes up on my ipad with the DJI app open, I have to follow the calibration procedure before the app will come on and be available for use.
     
  14. GadgetGuy

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    Very helpful information! Thank you!
    Does anyone know to what extent the Pilot app relies upon the iPad Compass calibration, independently of the P3P Compass calibration for stabilty?
    If my iPad Compass app is inaccurate, even after recalibration, will that throw off stability of a properly IMU and compass calibrated P3P in flight?
    Is there any way to repair defective iPad Compass or is that a defective hardware issue?
    Here is a comparison of my iPad Compass to a real compass, after several attempts to recalibrate it to fix the error. It's not a full 70°, but it is way off by 25° or so, in this image, and walking around with it, it was off by as much as 90° or more at times! My iPhone 6+ Compass app exhibits no such variation in the same area, nor does the real compass!
    image.jpg
     
  15. bobmyers

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    Don't put the real compass that close to the Ipad-- the edges of the Ipad are magnetic and will cause the compass you have next to it to not read properly-- it is in-fact pointing to your ipad and not magnetic north.
     
  16. GadgetGuy

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    Success! Thanks for everyone's help. Apple auto-updated my Pilot app to 1.2.0 late last night, so another variable has been introduced. I immediately started getting intermittent warnings before launch about unsafe flying conditions and to avoid long distance flying. This is new and led me to re-evaluate all other possible causes of interference. Pilot Arrow was still facing some 70° to the right of the P3P nose direction, so I again recalibrated the P3P compass and also completely removed the covered patio coffee table that I had been using for launching, and replaced it with a cardboard box to keep the P3P up off the ground and dirt and dust. The coffee table had been moved to the deck for a party last Saturday, which is when all the instability problems began, as I conveniently used it as my launching pad. Boneheaded move! Turns out the "coffee table" is actually an all metal firepit, covered with a wooden top and a table cloth, which hid the metal underneath. The Pilot arrow is now consistently properly aligned! Now my P3P flies like the gem it is.

    Lesson learned! Make sure your launching surface isn't hiding metal underneath it!

    The new Center Point reference for the Camera view in 1.2.0 is VERY helpful, too. It started sprinkling towards the end of my second long flight this evening, and just using the normal flight controls in P-GPS mode, I was able to quickly aim the new arrow at the new center point/home point by turning the craft slightly and then brought the P3P straight back at full speed in under 60 seconds!
     
  17. GadgetGuy

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    Good point! Actually, however, in this case they coincide, as within our house, the regular compass is, indeed, pointing in the correct direction of magnetic North, as confirmed by my iPhone6+ Compass App, which I couldn't use because I took the photo with it! I also held the regular compass up in the air some 2 feet above the iPad and shot a photo with it, which shows the iPad compass error.
    image.jpg
    Truth be told, however, there is also a metal frame in the table it is resting upon, that pulls the table apart, and the iPad reading might be influenced by that, just like the Phantom was on top of the metal firepit! :(
     
    #17 GadgetGuy, Jun 27, 2015
    Last edited: Jun 27, 2015
  18. bobmyers

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    Same thing on my patio-- metal table-- compass error-- Don't sit Phantoms on or near anything metal--:D:D:D:D
     
  19. snerd

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    I love happy endings!!
     
  20. GadgetGuy

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    Me, too! Couldn't have done it without you guys! If I had sent it off to DJI, I would have missed out on the next 6-8 weeks of flying! :D