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What happens if you fly P3 Off a Cliff?

Discussion in 'General Discussion' started by carlsagan, Jul 18, 2015.

  1. carlsagan

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    I'm near the Grand Canyon and wondering what will happen if I fly the P3 off the top of the canyon and hover it over the canyon? The drone will technically be only a few feet above the ground I launched from, but once it hovers over the canyon, it will be over 400 feet.

    I'm afraid it will think it's above the 400 feet level and start descending, is this a correct assessment?
     
  2. N017RW

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    All will be fine in terms of lift.

    However, any noticeable air currents rising or falling which may occur as you transition over the gap will of course carry the quad with it.

    You're not actually pushing off the Earth or ground once you're above ground effect height.
     
  3. Marlin009

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    No, altitude is from takeoff point.
     
  4. tcope

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    Nope. It will stay the same height it was just prior to going over the side. I have a video on this.


    I'm pretty sure most of the Grand Canyon area is a National Park (Native American section would not be).

    https://www.mapbox.com/drone/no-fly/

    You can get anywhere near the canyon.
     
  5. GoodnNuff

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    LOL, that sort of made me homesick. Not sure where in Utah that was filmed, but sure looked like the desert I grew up in in the Uintah Basin.
     
  6. tcope

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    Ironically enough, it's the Wedge Overlook, aka "Little Grand Canyon". It's near Castle Dale in central Utah.
     
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  7. GoodnNuff

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    Ahh, cool. Thanks. I wondered if it was near the Book Cliffs or Nine Mile Canyon.
     
  8. N017RW

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    Having been born, raised, and lived in Fla all my life, that place looks cool.

    We all yearn for something different I guess.

    But I digress.
     
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  9. LUISMARTINEZ

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    nothing, it will not just drop due to the aerodynamics involved, BUT you may piss off a park ranger, it's a no drone zone.
     
  10. LUISMARTINEZ

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    technically, incorrect. Any flight at any point above 400 AGL is a violation. If I launched my P3P from the top of the Empire state bldg. I'd be in violation. The "from take off point " language is nowhere on the FAA website. Please someone correct me, with reference, if I'm wrong.

    http://www.faa.gov/uas/model_aircraft/
     
  11. Marlin009

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    I don't think so. That is not what he asked. Re read his question.
     
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  12. N017RW

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    +1 Marlin.

    Not the OP's concern and the reference was not about AGL but if the FC would automatically command the a/c to descend once the a/c flew over the edge so as to maintain the same distance from the ground as it was from it's take-off elevation prior to.
     
  13. austin

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    Dude don't try to do it. Once the drone goes ovr the canyon there will be a difference in air pressure and in turn will cause a lot of electromagnetic interference. This will cause the drone to go up approx 100 feet, the stay stationary. Then aft a few more secs the drone motors will ovr heat and the drone will return to the launch point
     
  14. LUISMARTINEZ

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    are u going to contribute anything or just pick on me? EOD.
     
  15. Bryce

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    just do it... it won't be a problem. Probably safer to do it on the indian side.
     
  16. Ezookiel

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    Here in Australia, you'd technically be in violation of the 400 feet AGL limit the moment you went over the edge. My understanding from the CASA certified training I did, is that you have to be aware of your height AGL at the craft.
    However, it wasn't the legality the OP was asking about, but whether the bird would detect that it was over the legal limit and descend. I'm somewhat relieved to find that it wouldn't do so. I live in a very hilly area, and some of my favourite camping areas are canyons, where it's still legal to fly them if you're within the standard laws (daylight, LOS, under 400' AGL, 30m from people and property etc), so I'd hate to think that it would suddenly descend to legal heights if it went over an edge.

    The P2 is quite disconcerting to fly in very hilly and canyonous terrain. You have to have a good eye for your real altitude, because the altitude fed back via the FPV system really struggles to give a true indication of the height, and with the slow descent speed in places where the ground can descend faster than the quad can, it can be hard not to risk becoming technically too high.

    This is the most canyonous I've flown so far (with the full blessing of the Ranger who saw me doing the preflight routines, and asked me all about the quad, then said that National Parks haven't made a ruling yet, so go for it - since I'd already assured him I wasn't going to be putting it anywhere near other campers or their campsites).
     
  17. SteveMann

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    What rule would be violated??
     
  18. SteveMann

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    The phantom only knows the altitude above home point by the barometric altimeter module inside he NAZA controller. The GPS altitude is very unreliable. Even manned aircraft flying a GPS approach requires a barometric altimeter to get to the DA (Decision Altitude).
     
  19. LUISMARTINEZ

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    "The GPS altitude is very unreliable" Is there a source for this opinion?
     
  20. SteveMann

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    You should know better than to ask me for substantiation.

    Here's a test someone did comparing a GPS altitude measurement and a Barometric Altimeter measurement for the same flight. In just 150 seconds the GPS altitude was off by 16 Meters. [article]

    Here's another article the last line is pretty indicative: "Those who use GPS altitude to aid in landing their small plane should have their insurance policies paid up at all times.".

    Another article reads: "It is because of these errors that GPS must not be used as an altitude reference when operating close to the ground. You should NEVER use the virtual ILS function or VNAV functions of any GPS within several hundred feet of the ground under any circumstance."

    Environmental Systems Research Institute article on vertical accuracy [link] says "A brief examination of elevation readings for Esri headquarters in Redlands, California, demonstrates these differences. The campus elevation is shown on topographic quadrangle maps and high-resolution digital elevation models (DEMs) for the area as approximately 400 meters above MSL. However, a precise, nonadjusted GPS reading for the same location typically shows the elevation as 368 meters."

    Even the sports GPS devices use a barometric altimeter to record altitudes. [link]

    The GPS altitude changes as the geometry of the satellite position changes. Here's some government documents explaining the math.
     
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