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WARNING: Home-point Reset by Interference During RTH

Discussion in 'Phantom 2 Vision Discussion' started by PVFlyer, Apr 13, 2014.

  1. PVFlyer

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    As I lost my P2V several weeks ago due to unknown reason, I probably figured out why my P2V went down. My friend experienced the exact same scary case recently.

    My friend flew his P2V the same path as I did several weeks ago. When he initiated RTH 500M away at 100M altitude, and his P2V was flying back as usual until 200M away from the home-point (almost the same spot as I lost my P2V), his P2V started auto-landing right into the pond. Why the hell P2V was auto-landing 200M away from home-point? When he was aware the aircraft was landing, he regained the control immediately at 50M altitude and flew back manually. When he flew back home-point (the real one), the Vision app indicating 200M from the home (fake) position.

    I know switching S2 (left switch) multiple times can reset the home-point during P2V in the air. I suspect some sort of RF interference switching S2 at such spot 200M away during RTH. Thus P2V believed it's back home, then executed auto-landing.

    This is likely a software/design bug (or feature) of the NAZA flight controller for all Phantoms (including P2, P2V, new P2V+ & probably P1). I strongly urge DJI to put a better safeguard of reset home-point in the air.

    I know it's handy to reset home-point for those take-off/landing on boats/trucks. But it does NOT make sense to reset home-point during RTH. This could be an easy fix in the firmware to disable reset home-point temporary "during RTH process", and re-enable it upon regain control.
     
  2. Ozzyguy

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    This is likely a gps signal problem. Gps is les accurate the less satellites that are available. This dan greatly affect accuracy.
     
  3. PVFlyer

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    I initially thought it was getting less than 6 satellites during RTH, then it executed auto-landing. But the logic is when my friend flew back to the real home-point (probably with 9 satellites), Vision app showed 200M away. This indicated the home-point was reset above the pond. Anyway, it should NOT reset home-point even it gets less than 6 satellites.
     
  4. Geoelectro

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    I wonder if it could be an intermittent switch/connection on the controller. I had to resolder a connection on mine after only a month old.

    Geo
     
  5. PVFlyer

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    I don't think of intermittent switch, while it needs switching S2 continuously 5 times to reset home-point. Furthermore, this happened 2 exact coincidences on 2 different P2Vs with the same flight path and same fake home-point auto-landing. It could not be coincidences.

    Thus, I strongly believe this is caused by RF interference. In fact, such reset home-point feature was introduced in Nov-2013. DJI also implemented triggering RTH if >10 seconds with exact same command in order to avoid flyaway.
     
  6. BenDronePilot

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    That's a possibility. The DJI manual states that there are two different behaviors of RTH depending on the satellite connections. or three if you count taking off without first having satellite lock.

    Assuming you initially took off with a home lock of your position for take off the following will happen should you enter fail safe mode and you have + or - 6 satellites.

    If you have less than 6 satellites for any reason during a fail safe operation your Phantom / Phantom 2 / Phantom 2 Vision will begin landing where it is.

    If you enter fail safe and have 6 or more satellites you're Phantom will ascend to 66 feet or stay at it's current altitude if higher than 66 feet, fly back to your home position, hover for a moment, then land.

    If you enter fail safe without having had a home lock before take off you will always land where you are if entering fail safe.

    Resetting your Home Point while in the air requires flicking the S2 switch down and up 5 times. You will see a visual confirmation of the tail lights on your Phantom quickly flashing green. It also does not matter if your new home point is at a lower or higher elevation than your first home point. Your Phantom will still land fine.