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Flying High

Discussion in 'General Discussion' started by phabixio, Sep 20, 2013.

  1. phabixio

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    Hi Phantom flyers
    Great forum full of precious info!!
    I have a phantom with a FPV immersion 600MV transmitter and a gopro Hero 3 attached, no gimbal as yet.
    I m planning to take of from a tall building for the first time to get some nice shots of the streets. Before I make such attempt I wonder if anyone has done it and could clarify some doubts.
    - I noticed the phantom at full load doesn't reach the same hight as when it s flying without gopro and transmitter. I am wondering if as soon as it gets out of the building perimeter it will drop down to a hight it can sustain and it won't be able to rise back to where it took off!!!
    - If it should get out of the range of the transmitter and the RHF would kick in, would it go down to 25 mt hight above the ground even if the home point is much higher than 25 mt?
    Thanks a lot for any hints!
    F
     
  2. Loppy

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    That is not making sense. The load and or overall weight of the Phantom should have nothing to do with how high (altitude) it can travel. It may effect how FAST it gets there, but not the altitude.

    As well, setting the home point (power up, sat acquisition and motor start) should also remain unaffected if taking off on a rooftop. RTH I would think, would return the bird as usual. However, I would caution that most building roofs are mired in electrical lines, mechanical equipment and other things that can conflict with RF singnal, compass and or GPS. Make sure you have a good startup procedure and RF lock. Good luck, post vids!
     
  3. TickTock

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    I hope you have lawsuit insurance. Sounds very dangerous - especially with a craft that is notorious for loss of control.
     
  4. MrMediaGuy

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    Will be interesting to see the opinions on this one. :)

    As far as gravity is concerned, it doesn't get any stronger the closer you are to the ground. (Well it does, but only in a nano sort of way, which isn't relevant here...) So I guess I'd ask first....what all are you carrying on that thing? I have Zenmuse, GoPro, Immersion TX, Skylark OSD, and a Garmin GTU 10, and I can get to 125m (or higher, if that were legal in the US) in a matter of seconds with the stock props.

    If your Phantom flies with the load you are carrying, it will continue to gain altitude at full throttle at whatever rate it is able to, whether you are 20 feet AGL or 300 feet AGL. The limiting factor is time -- the heavier the load, the slower the rate of ascent. If your motors are stuggling and you're only ascending at 2m/s or something, you'll keep going up, just not as far over the same amount of time. Also remember that the Phantom doesn't know if there is a building roof underneath it or not (except when you are in ground effect -- but if your Phantom will only stay airborne really close to the ground, you have other issues with weight).

    Now, as to your question on RTH home behavior, I am going to take a GUESS, but I want to say it is purely a guess. Since the NAZA can auto-land, we know it records "where the ground is" when the home point is locked. I'm going to guess it does that using the barometric altimeter and not using GPS altitude data, since the vertical error on GPS is way to large to allow landing with any finesse. (Although there may be an algorithm that factors in the GPS altitude as another data point.)

    In that case, *if* you were to be unfortunate enough to end up in a RTH situation, I am fairly certain the Phantom would go to 20m above the takeoff point, not 20m above wherever it is at the time, since it doesn't know where the "ground" is once you leave the perimeter of the rooftop.

    That's both good and bad. Good, because it means it wouldn't shoot down from 100m to 20m -- but bad because if the home lock isn't very precise, it could try to "land" a meter or more away from the edge of the building roof (particularly if you took off from too near the edge in the first place). And that would be very bad. :)

    So the lesson here is, *please* be very careful flying in a situation like this. You really shouldn't do it at all unless you have experience, proper permits and permissions that might be needed, as well as a good understanding of safety -- e.g., only do this when the area is as devoid of people and cars as possible so you aren't flying over anything you might damage.

    And if you do it anyway, exercise every caution you can to remain in control of the quad at all times -- meaning DO NOT get in a situation where RTH might activate, and if it does, switch into ATTI immediately and try to regain control. You don't want this thing flying itself around buildings, streets, towers, antennae, people, wires, etc.

    But the best advice would be, don't do it. :)
     
  5. phabixio

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    Hi
    Thanks a lot for the answers, I value all of your comments. I am far away from being an expert, (but looking forward to become one :ugeek: and shopping around for a bigger bird) as I have been flying only toys and got my phantom a couple of months ago, although I am flying it since pretty much every day using all of my 6 batteries.
    Security issues are paramount to me, that's why I am collecting as much as info as possible and I am simulating as close as possible these conditions in controlled environments before deciding whether or not to take the risk.
    It amazes me how very little certain informations are available around some aspects of the engineering of the NAZA eg which factors come into play between the barometric altimeter and the GPS in different situations.
    I ll keep on researching and if I ll end up doing it I ll post the outcome.... hopefully not from jail ;)