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First Scare & Strange Behavior in Attitude mode...

Discussion in 'Phantom 2 Vision Discussion' started by James Cole, Dec 14, 2013.

  1. James Cole

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    Hello guys!

    Had my first scare today!

    I was flying my P2V on a big field today and decided to try Attitude mode non GPS, The phantom seems to fly much faster so this mode seems situ able for sport flying... Sooo I gun it and it went like stink about 25m/s which equates to 90 km per hour or around 57 miles per hour... until suddenly I saw that the Phantom was losing altitude very quickly in the direction it was traveling... I give it some lift to stabilize but It was going so fast that went out of range quickly!

    Connection was lost and I kind of saw the phantom traveling even further away! I thought it was flying away... then it suddenly stopped and returned home perfectly, Flipped the S1 switch and regained control.

    So I am happy the return home worked perfectly... Only that I am bit worried about Attitude mode not holding altitude... whats up with that?? I tried it a second time... full speed forward and it started to lose altitude again... but only while going very fast...

    Is this normal...?

    Thanks in advance!
    JC
     
  2. PhantomFan

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    Think about it for a minute and you will know the answer. Attitude mode voluntarily "excludes" the GPS data (until signal is lost) from your Phantom's scope of assisted flying. When you pitch the machine hard forward, the lift vector is more forward and less UP, so you lose altitude - just like they taught you in physics class.

    PF
     
  3. jimre

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    I guess I thought the Phantom attempted to maintain level altitude while in ATTI mode. Is this not the case?
     
  4. James Cole

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    Exactly...

    PhantomFan your point is very valid as well but Attitude mode is supposed to hold attitude... so whats the deal here?

    Have other experienced the same behavior?
     
  5. dkr77573

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    First Scare & Strange Behavior in Attitude mode...

    Attitude is not altitude. It is simply the horizontal orientation of the phantom. By pitching in either direction with the controller, you're telling the Phantom that you want it to GO, which can only be accomplished by leaving said stable attitude. However, when you release the controller it will return to that flat horizontal position.
     
  6. PhantomFan

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    I thought it would only recover attitude (level flight), using the gyros to auto-level in ATTI Mode, but I could be totally off-base here. In any event, the loss of altitude is through the mechanism I described.

    If you are correct and there should be maintenance of altitude as well, I recommend you go to the NAZA Assistant and up the vertical gain AND review the mounting location of the CG relative to the GPS. You may have added too much gear that 1) increased the weight and, 2) shifted the CG forward, resulting in the drop.

    PF
     
  7. jimre

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    Right. But being a newbie pilot, I watched Colin's DJI video explaining ATTI mode - and came away with a clear impression that the aircraft was free to drift in any horizontal direction, but would stay at the same height. If that's actually NOT true - and I got the wrong impression from the video - then it's good to know before I start testing ATTI mode next week.
     
  8. Celt in Siam

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    Could it be that the motors are experiencing a slight voltage drop given that the P2V is being flown a maximum speed?
     
  9. BenDronePilot

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    What you experienced is normal and why DJI had only GPS mode available as the default flight option so new pilots can fly and enjoy the aircraft without getting themselves into trouble by flying in atti mode of manual. There's good reason for that warning message when switching to NAZA James shouldn't be pushing it as he did without proper flight experience and taking more baby steps.
     
  10. Sidewinder

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    pull the pole, the houses get smaller, push the pole the houses get larger. That's the function of your cyclic. You only can produce so much power. at max power (throttle) there is still a limit to maintain level flight. In attitude you have command to maneuver anyway you wish with the controls. I would think that with the input of any control position the aircraft would respond accordingly ..... you let go of the controls from any input and any attitude they should center and the aircraft should respond likewise .... stop and hover.

    I only flew my phantom vision for a few minutes when the camera and wireless failed and pissed me off. So I sent it back for a refund or replacement but all my other multirotors work in this fashion although there's different terms for the three modes of flight.

    I would ask you consider the relation between power and angle of attack. When you push the cyclic forward from a stable hover without any additional power there is a point where the aircraft will descend without more power to keep it in level flight. If you slam both sticks full forward, one is saying put my nose down and the other is requesting max power. If there is plenty of power available the nose will point downward and the power will thrust the aircraft forward and up. Once the power and nose down attitude sort of reach a balance, should you maintain full forward on the cyclic the aircraft will begin to dive.
    If there's unlimited power the aircraft will climb with a nose down attitude producing faster and faster forward flight. Physics being what it is, there is a limit to just how long you can just stick the cyclic full forward without beginning a dive.

    Not sure if I'm making sense to you but that's basically what's happening.
     
  11. Pull_Up

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    Agree with all of the above. My understanding has always been that attitude mode will maintain a level attitude when you let go of the sticks. Let go of everything and it will maintain height and level attitude. Otherwise it assume you know what you are doing and will therefore allow effects as so excellently described above.
     
  12. dkr77573

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    Re: First Scare & Strange Behavior in Attitude mode...

    I think it's important to remember that in the demo video, he does state that in ATTI mode the Phantom will be subject to the wind and momentum. I'm willing to bet this would also apply to down drafts (which he did not experience). If a down draft was stronger than the idle lift, the altitude would decrease. However, it would drop with a flat/stable orientation. ;P