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Losing the 6th satellite

Discussion in 'Phantom 2 Vision Discussion' started by Will Rockwell, Jan 4, 2014.

  1. Will Rockwell

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    New pilot here, I've had only one day of flying but have a question. On my third short flight, the Vision tilted sideways on the pavement and did not respond to an engine power-off command. As I was doing my pre-flight I noticed the satellite count changing from 5 to 6. What happens if that 6th satellite connection is lost and there are only 5, could that be the cause of the strange behavior? Should I have pulled the S1 switch to the down position?
     
  2. sangfhas

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    it not need switching s1 it still fly stable but the position may not accuracy .
     
  3. AnselA

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    Location:
    Declination +8° 11'
    Firmware Updates on Dec.19

    "Major New Features:
    a) In a Failsafe situation, if less than 6 GPS satellites are found for more than 20 seconds, the aircraft will
    descend automatically."
     
    Bob Royall likes this.
  4. iDrone

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    After touchdown always stop your motors with a Left Stick Down until they all come to a stop, them release the stick. DO NOT do a CSC else it may flip!!!

    iDrone
     
  5. garygid

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    Location:
    Laguna Hills, Orange county, CA 92653
    Assuming normal default Vision mode operation:

    If you take off and fly with 5 or less GPS satellites locked, are you flying in Atti mode?

    To set Home position, you need 7 or more GPS satellites locked, right?

    If you are flying with 7 or more satellites locked, you are in Vision-GPS mode, and there
    is no way that you can get out of it and retain control, even if there is some GPS-Compass
    conflict that is causing the P2V to fly away, right?

    In this case, the novice flier has only one recourse, which is to turn the RC Transmitter
    Off, and hope that the confused P2V might try to fly home, which is unlikely, since the
    P2V is already so confused that it is attempting to do a fly-away, right?

    The P2V's Atti mode does not use the GPS, right?

    So, if the novice had Atti mode available, and a fly-away was starting, switching to Atti mode
    might allow recovery of attitude (and altitude?) stabilized flight control, right?

    Am I missing something important, or does the novice have insufficient control to stop a fly-away?

    Thanks for your patience, I am trying to learn, and some of these things are confusing,
    or at least insufficiently documented, in my opinion.
     
  6. Pull_Up

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    Location:
    South Oxfordshire, UK
    As there has been no one "smoking gun" cause for flyaways found it's hard to tell. I have seen people confirm that they have rescued a flyaway by switching to manual mode, rather than atti. I am assuming that this is because although atti mode no longer uses GPS to hold station horizontally it still uses compass/GPS data for orientation control (it needs to know which way its pointing in order to keep pointing that way, if you know what I mean). Manual mode doesn't use compass, GPS or barometer so the theory goes if you are quick enough to catch it, you can bring it back (or more likely crash it if you've not got your manual flying "wings" yet, but the crash will be closer to home).

    I've seen a YouTube video somewhere of a guy running a NAZA controller on a pro hexa or octa rig that was behaving badly and filming being able to arrest the start of a flyaway using manual. When he flipped it back from manual the flyaway would start again. I'll see if I can find it...

    EDIT Here it is: http://www.youtube.com/watch?v=iW0hqzixwsk Note it's not with a Vision (or even a Phantom) but it is a NAZA controller. Obviously there have been firmware updates since this, and indeed the Vision may have an entirely different version of the NAZA in it (I don't think so, though - the development cost would have been large - I think it's just firmware limited/modified) but it was interesting to watch nonetheless.
     
  7. gunslinger

    gunslinger Moderator
    Staff Member

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    Location:
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    Looks exactly like the "spiral of death" caused by a confused compass...

    -slinger
     
  8. LeoS

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    If GPS\motor\user error cause flyaways...

    We should be calling compass errors flushaways...
     
  9. gunslinger

    gunslinger Moderator
    Staff Member

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    Location:
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    Do they spin counter clockwise in Australia??? ;)
     
  10. LeoS

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    I've just viewed that video too, and it convinced me that ATTI mode does not use the GPS nor the compass... and simply relies on gyro (and altimeter) to keep the craft level.

    Of course going manual will completely disable the fly-by-wire nature of NAZA and be the 'safest' way to avoid any interference\sensor failures, but most mere mortal (and noobs like me) can't handle that mode safely =P

    Thankfully the guy in that video also suggested to use ATTI mode in a flyaway situation :)

    Dunno about that... but they stink all the same :lol:
     
  11. BenDronePilot

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    Problem is you took off your Phantom too soon to begin with. You should wait with your Phantom on the ground till it maintains a stable lock of 6 or more satellites for no less than 30 seconds though I will wait as long as a couple of minutes depending on my environment. If I take off in my back yard GPS has a harder time locking properly so it can take a couple of minutes to maintain a sold GPS lock of 6+. When I fly at the park however satellite lock is much faster and I can take off sooner with less concern.

    If you don't wish to wait too long on the ground before take off. At the very least make sure your Phantom did a "Home Lock" before take off which is indicated by the tail lights quick flashing green, followed by a solid green. You can immediately take off if you really want to, but if you're only at the minimum of 6 satellites when you do there is always the chance you will drop down to 5 again.

    Flying with less than 6 satellites means the following will happen. 1) If you hit the fail safe either by flying beyond controller reception, or by shutting it off. Your Phantom will auto land where it is and NOT fly back to the home position it took off from. 2) The Phantom will behave more as if it were in Attitiude mode, minus the more responsive controls (attitude mode has much higher gains set on the stick control vs GPS mode. What this means is your Phantom can be easily blown away from you and our of range should a gust of wind hit you. If you get pulled out of controller range and still have less than 6 satelites, refer to point number 1.

    Info regarding "Attitude" mode. Attitude mode is not available out of the box. Firstly, for a new flyer I would leave things as is. If you become more experienced then you can go to the DJI assistant software and first enable "Naza" mode which you get to by clicking "Phantom 2" on the top right of the application. Naza mode will enable Attitude mode. By default Attitude mode will be available by moving your S1 switch to the middle or lower positions. Alternatively you can customize the bottom position of the S1 switch to instead enable the "Fail Safe" mode (without having to turn off the controller) or "Manual" mode (absolutely do NOT fly in Manual mode, you will most likely crash, badly) Be careful if flying in attitude mode. First, if flying and you let off of the controls your Phantom will keep moving in the direction you were flying, it will not quickly stop on it's own as in GPS mode. It also takes less movement to move your Phantom quickly. Aggressive forward movement will drive your Phantom straight into the ground as it's not using GPS to hold your altitude position. You can also fly a lot faster in Atti mode, up to 50mph versus around 35mph or so in GPS mode so you can easily fly out of visual or transmitter range if not careful.

    With Naza mode enabled you can also turn on IOC "Intelligent Orientation Control" under advanced. Which gives you the following two modes. S2 switch up, off, middle, Course Lock, S2 switch down, Home Lock. With course lock on, lets say you take off with your Phantom 2 Vison directly in front of you and GPS locked. regardless of which direction you point the nose, moving the Forward Back Left Right controls will always do just that, and not get reversed or mixed up, like if you had the nose of your Phantom pointing at you, or sideways. Home Lock works when your Phantom is more than 33 feet away from the "Home Locked" position. Keeping in mind you must have good satellite lock. When you switch to home lock, regardless of which way the front of the Phantom is facing, or where it is in the sky. Pulling back on the right control stick (assuming you didn't change your controller from mode 2 to mode 1) will always fly the Phantom back in a straight line towards the marked "Home" position.

    I hope that helped, and was not too much information for you starting out. Please read the top three threads for some more helpful information for new pilots. And especially as a new flyer try not to fly too far out of your comfort zone. it's also a good idea as a new flyer to keep your initial few flights in a very open grassy field so you have less chance of crashing into something, or someone.
     
  12. rotaryboots

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    Thank you BenDronePilot for posting that reply. DJI didn't exactly this change when they began sending P2's with the "Phantom" labeled Naza FCs.

    Thanks
     
  13. gfredrone

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    Sounds like you did a CSC and didn't hit the diagonal move of the sticks perfect. Then you panicked seeing it flipping over in slow motion, nnnnooooooooooooo, as the blades made their way toward the pavement. This is where the grit hit the fan, pun intended. Same thing happened to me on my 3rd flight. Luckily no damage done except having to clean grass stain from the props with some alcohol wipes.

    Probable cause is your right stick move was quicker than your power down move. If you are quick on the right stick without first powering down, you are telling the P2V to go in a backward left direction with power still applied, and over she goes. If you miss the CSC command with the left stick and your diagonal move is off a little, you will be telling it to yaw right.

    Like idrone said safest way to power down after touchdown is to just hold the left stick all the way down until the motors stop. I've gotten pretty good with the CSC but I always move the left stick to the all the way down position before doing the CSC.

    Don't just go diagonal over to the the bottom right position. First down then over. This has worked for me after learning my lesson with one flip in the soft grass.

    So to sum it up;

    1. left stick straight down to bottom position, hold down and the props will stop after about 5 seconds.

    or

    1. left stick straight down to bottom position (right side remains in center)
    2. at the same time move left and right stick to inside bottom corners.

    Walk off a winner without incident! :)