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Afraid of using "full descend" ?!

Discussion in 'Pro/Adv Discussion' started by ShelbyPoker, Apr 4, 2016.

  1. ShelbyPoker

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    Hi

    When flying my P3A, It's always with a bit of fear when descending !

    The reason ? Well, when the bird is landed and you want to stop the engines, you can do it by pulling (and holding) the left stick all down - that's fine

    But, I always have that in mind when descending and pulling that left stick all the way down.....what if the bird all of a sudden, mistankenly, thinks that it's on the ground and then shuts of the engines ???

    How do the bird know that it's landed and how does it know when it's airborne ?

    Am I just seeing ghosts from al that "falling from the sky"-reading on this forum ? :) ...or is a real threat
     
  2. N017RW

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    The prevailing thought is that it uses [just] the barometer to determine it is no longer descending but as time has passed I believe it is using the IMU as a whole in that the accelerometer and gyro are used as well.
     
  3. With The Birds

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    You could be right, accelerometer value would be back at a stable -1Z when stationary (landed). Barometer alone may well be not accurate enough.
     
  4. 4wd

    4wd

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    There is a slight risk of instability due to Vortex Ring State.
    They've more or less done away with the risk by canting the motors a few degrees in the P3, but you might still note a tendency to wobble.
    No risk at all of shutting off until descending stops.
    Provided you don't do a CSC ...
     
  5. Mark The Droner

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    But the important thing, I think, is there hasn't been a single case (that I've seen on this site ) of somebody complaining that their motors shut down while in full descent. That alone should quell most fears.
     
    Ross likes this.
  6. alokbhargava

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    Your fear is reasonable. Anything can happen if electronics fail or if there is a glitch in the SW. We got to be prepared for it.

    The built in logic is simple, if bird can't further descend with full stick down for 3 seconds and stays at the same location, motors stop. This condition occurs when bird lands. Can such condition occur in any other hypothetical situation while the bird is still in the air? Can the bird hang in air during extreme windy conditions? Possibly No.
     
    #6 alokbhargava, Apr 4, 2016
    Last edited: Apr 4, 2016
  7. Meta4

    Meta4 Moderator
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    Two reasons not to worry.
    DJI designers aren't that dumb .. and if they were the manual would have a big warning and we'd all have crashed in our first week.
    Full left stick down descent has been heavily tested by thousands of users with no hint of a problem.
     
  8. Reed L

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    As long as I'm in P- GPS, I use full descend every flight. The only time that I haven't is when flying in P- Atti mode because of loss of GPS or none to begin with and that's a different type of flying style anyway.
     
  9. Erroll

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    One lands and shuts off the motors in the same manner in ATTI mode.