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Phantom 2 Vertical Stability

Discussion in 'Phantom 2 Discussion' started by calipilot, May 2, 2014.

  1. calipilot

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    When I am flying and filming I am noticing the Phantom moves vertically up or down when I am not moving the throttle stick up or down. If I am flying in a circle around something and filming it will descend slightly instead of maintaining a consistent altitude.

    I have used a Futaba radio on a F550 and don't recall this being an issue. I assumed with the self centering stick on the Phantom 2, this would be even easier to maintain.

    Are there any settings I can change to fix this or is this just the characteristics of the copter? I know it is small and light, but still powerful.

    Thanks!
     
  2. thedjiguy

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    Go into the Naza and recalibrate the IMU. Then before your next flight, recalibrate the compass. This should fix the issue.
     
  3. OI Photography

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    Does it exhibit the same behavior when you're in ATTI mode as it does in GPS mode?
     
  4. usaken

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    Here's a little tidbit from airplane pilot airmanship. One of the things you learn as a pilot is to manage energy. When you initiate a turn from straight flight, it takes some of the stored energy to break the inertia and turn the plane. If you don't pull back on the yoke a little the plane will decend throughout the turn. if you don't old back the yoke then you are trading altitude to make the turn. If you do hold back the stick you will maintain altitude but trade speed for the turn. As a result of holding the stick back you will also slow a bit. I suspect something like this here.
     
  5. WessexWyvern

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    Lift from an airfoil acts perpendicularly to it and continues to when you bank so when you turn, the force from the wing (or propeller)is no longer acting straight up so to in order to compensate for the reduced vertical component of lift you either need to increase the angle of attack (you can't, the props are fixed) or increase their speed. This you can do...or at least the Naza can do it for you. So I'm not sure if this is the problem...not saying it isn't but I'd be surprised if such a simple adjustment can't be made by the flight computer. Isn't that the whole point of flight computers, to take those sort of decisions out of our hands and allow us to just get on with what we want to do without thinking of those sort of technicalities? Unless you are in manual mode - I have no idea how much control is handed back to the pilot in this mode ?

    If recalibrating doesn't fix it, one possible answer could be due to the inherent inaccuracy of how a GPS gets it's altitude fix and is summed up in this snippet from the Garmin website "the accuracy permitted by geometry considerations remains less than that of horizontal positions". It's odd you didn't experience it before but compensating for a reduction in the vertical component of lift can't be beyond the wit of DJI...can it? Maybe in the instances where you experienced a descent you were receiving reduced satellite coverage?
     
  6. ianwood

    ianwood Taco Wrangler
    Staff Member

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    GPS is not used for altitude as it is much too imprecise under 10 satellites. The barometer is used for vertical positioning and while it relatively much more accurate than the GPS, it is not precise enough to keep the Phantom at exactly the same height. The gyro and accelerometer help in that regard but when you are moving, they are too and their precision will be effected.