Welcome to PhantomPilots.com

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

P3 Pro unstable during landings

Discussion in 'Pro/Adv Discussion' started by tgilbert, Dec 26, 2015.

  1. tgilbert

    Joined:
    Aug 19, 2015
    Messages:
    26
    Likes Received:
    4
    Location:
    Brisbane, Australia
    I am seeing increasing instability in my P3 Pro during descent and landing and I wonder if something is going wrong with it?

    First few flights I was amazed by how well it landed at the home point and how smoothly it descended. Have now flown about 20 flights and sometimes it misses the home point by a couple of metres. In descent it wobbles and even rotates, even on RTH descent. I've had to start cancelling RTH about 10m above ground and landing manually.

    Is this likely to be prop balance? I've balanced the props but who knows how well? Checked solar levels yesterday when it wobbled badly, thinking it may be GPS interference, but K=1 and I was out in the wide open spaces so nothing to interfere with GPS. 20 satellites.

    I probably should start hand catching but with it wobbling like that I'm not sure I want to risk my wrists!
     
  2. msinger

    Approved Vendor

    Joined:
    Oct 30, 2014
    Messages:
    19,056
    Likes Received:
    5,611
    Location:
    US
    Wobbling during a descent is usually an indication of VRS. That can be easily avoided by using stock props and not descending straight down with the left stick in the full down position.

    FYI, if you're using the auto takeoff and landing features, I'd recommend you learn how to do it manually instead. You'll be able to manually fly with much more accuracy. Perhaps after a bit of practice too ;)
     
    snowghost likes this.
  3. tgilbert

    Joined:
    Aug 19, 2015
    Messages:
    26
    Likes Received:
    4
    Location:
    Brisbane, Australia
    Only using stock DJI props. I have two sets, but have only used one set so far. Not sure how long they last. I might pull the second set out and see if I have the same issues.

    I am landing manually more and more now. Mostly use RTH only when I've been doing something complicated and can't be sure I'm still pointing where I thought. But I'll try landing with less down stick and see if that improves the stability.
     
  4. George Race

    Joined:
    Dec 10, 2015
    Messages:
    159
    Likes Received:
    66
    Location:
    Albion, MI
    Just a thought, I read somewhere that it would be wise to do an IMU calibrate after every software update. That could effect stability.
    Also make sure that the bottom looking camera and the ultrasound sensors on the bottom of the bird are clean.
    GR
     
  5. msinger

    Approved Vendor

    Joined:
    Oct 30, 2014
    Messages:
    19,056
    Likes Received:
    5,611
    Location:
    US
    Speaking of that, you might see better results too if you turn off VPS. It was designed to be used indoors.
     
  6. tgilbert

    Joined:
    Aug 19, 2015
    Messages:
    26
    Likes Received:
    4
    Location:
    Brisbane, Australia
    Agree but I don't think that's the issue as the wobbling is apparent 20-30 metres above ground. Don't think VPS works at that height?
     
  7. msinger

    Approved Vendor

    Joined:
    Oct 30, 2014
    Messages:
    19,056
    Likes Received:
    5,611
    Location:
    US
    It's possible. But, I suppose a set of severely damaged props could have caused the same thing. I'm assuming that wasn't the case though.
     
  8. tgilbert

    Joined:
    Aug 19, 2015
    Messages:
    26
    Likes Received:
    4
    Location:
    Brisbane, Australia
    Definitely no visible prop damage. Just recalibrated IMU to see if that makes any difference. Will try the other prop set too just in case.
     
  9. msinger

    Approved Vendor

    Joined:
    Oct 30, 2014
    Messages:
    19,056
    Likes Received:
    5,611
    Location:
    US
    Going back to your original post above, are you saying this happens when automatically landing or also when manually landing? The automatic landing is at a pretty rapid descent (I believe equivalent to full stick down). Try manually descending with the stick at about 75-80% down and see if the same thing happens.
     
  10. tgilbert

    Joined:
    Aug 19, 2015
    Messages:
    26
    Likes Received:
    4
    Location:
    Brisbane, Australia
    I'll try that too. Just waiting for the weather to clear a bit so I can go out and fly. Queensland, beautiful one day, just not today.
     
  11. Meta4

    Meta4 Moderator
    Staff Member

    Joined:
    Jan 8, 2014
    Messages:
    7,754
    Likes Received:
    3,466
    Hi TG ...Wobbling and/or rotating during descent doesn't sound good but what's causing it is a bit of a puzzle.
    Is it still unstable if you control the landing rather than leaving it in auto? How about just hovering?

    The accuracy of RTH landings will vary since GPS accuracy is variable. Most of the time it will be within 1-2 metres but it can sometimes be more than that.
    Cancelling RTH and resuming control is a good idea anyway since you can probably see and land better than the Phantom.

    It's definitely nothing to do with GPS or K-index, neither would have the effect that you've described.
     
  12. tgilbert

    Joined:
    Aug 19, 2015
    Messages:
    26
    Likes Received:
    4
    Location:
    Brisbane, Australia
    Just tried it in the driveway with the new prop set, IMU calibrated, compass calibrated (because it demanded it), hovering at 2m in P Mode it was moving more than a metre side to side. Had to quickly bring it down again because I don't have a lot of space out there (trees, roofs, etc).
     
  13. Musicman666

    Joined:
    Dec 1, 2015
    Messages:
    8
    Likes Received:
    1
    Did You put a spirit level on the table to check it was level?

    Also best try doing it first in an open field ...my first flight in the back garden did the same thing and collided with the neighbours wall ...not totally sure why but best you iron out these issues in open space.

    Also get some prop guards to save stressing the props if things go wrong.
     
  14. jack1144

    Joined:
    Jul 12, 2015
    Messages:
    74
    Likes Received:
    23
    I know you tried a compass calibration, but the rotating and wobbling sure sounds like compass error.
    Did you try compass calibration in a place where no sources of metal , electromagnets,etc are located? Open field near you would be good.
    Is the compass value very near 1500?
     
  15. Meta4

    Meta4 Moderator
    Staff Member

    Joined:
    Jan 8, 2014
    Messages:
    7,754
    Likes Received:
    3,466
    The reason your Phantom informed you that that there was a problem with compass calibration was because the compass detected a significant difference between the magnetic field and what it expected.
    You had your Phantom on top of steel reinforcing mesh in your concrete driveway.
    Recalibrating in a situation like that is asking for trouble.
    You calibrated for the distorted field close to the steel and when your Phantom gets further away, the compass is swinging all over the place.
    Learn what compass calibration is about and when to calibrate to fly safer.
    Compass Calibration, A Complete Primer | DJI Phantom Forum