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Flyaways and BTSs

Discussion in 'Phantom 2 Discussion' started by Exsniperex, Nov 21, 2014.

  1. Exsniperex

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    Hello
    I`d like to share my first experience with “flyaway”. Before that fly I did all necessary things from my check list:
    1. Ajusting the temperature of the quadrocopter to the outdoor one (7-10 min.)
    2. Fixing to more than 6 sats.
    3. Compass calibration.
    4. Starting the timer (alarm on 14 min.) after turning on the engines.
    5. Checking the proper HP (home point) by flying in a circular in HL mode.
    After 10 min and 23 sec. of stable flight my Phantom suddenly lost control. I managed to turn off the controller. The Phantom stabilized its flight and was heading to HP. Not so long after a few sec. it speed up to 55 kmph just in the opposite direction to the HP. I switched the controller off again and in a few sec. the Phantom started its way back to its HP. I was afraid that the reason of “flyaway” was caused by loosing sattelites so I decidet to switch to manual mode. That was a mistake because the copter fell down from 15 meters to the ground. I found it in one min. thanks to remembering the direction of last seen position and my tracker installed on Phantom. I was very surprised when I found that the copter, the gimbal, GoPro B3+ and tracker were intact. Only the battery slipped from the copter.
    After that experience I downloaded data from my FLYTREX Core 2 unit just to analize the flight parameters. I was surprised when I got to know that the number of sats was 10-11. It was obvious that GPS fix was OK all the time of the flight. I focused on the terrain to find out what caused the flyaway. Examining the track of the Phantom in Google Earth I was surprised that the direction of “flyaway” was in one direction. I know that there weren’t any dangerous antennas or metal structures. The nearest BTS (base transceiver station) was 2.16 km SE. I realized that the direction of “flyaway” was exactly the same as the direction to the BTS. It`s well known that flying close to BTSs can interrupt connection with any radio controlled units but what distans is safe? I found out that there are mostly two types of antennas that are used in BTSs: sector and directional ones.
    The directional antennas work by focusing energy in any sort of direction other than just letting it radiate at random in all directions. I let to plot straight line from “my “ BTS to nearest one and the line matched exactly the “flyaway” track. I realized that my quadrocopter crossed the radio beam from one of directional antennas mounted on BTS. That experience tought me that I should add another number to my check list:
    6. Plot straight line from the nearest BTS to all in distance about 20 km then avoid crossing the lines.

    Please check Your "flyaway" sities to proove it.
     

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  2. malibusteve70

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    How'd you find out where the BTS was located? Are you in the USA?
     
  3. Exsniperex

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    In Poland. In EU works BTSearch. Check if it works in US too.
     
  4. knuckles

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    Location:
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    Are you talking about BTS for cell service? Those kind of antennas are everywhere in the US to improve cell service.
     
  5. Exsniperex

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    Frankly speaking like in the rest of the world. The key point is that BTS consists of many types of antennas including the directional ones.
     
  6. ianwood

    ianwood Taco Wrangler
    Staff Member

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    The BTS itself doesn't radiate any signal. The antennas connected to it do. At that distance, it is unlikely that they had any influence unless they were malfunctioning in a very unusual way. Also, GPS problems are an uncommon cause for flyaways.

    What was your distance to the Phantom during the loss of control? You mentioned you turned the controller off twice and each time it began a normal RTH. Did it start to fly away when you turned the controller on the second time? Possibly it was something to do with the controller.
     
  7. Exsniperex

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    Thats the point. The directional antennas are the problem. Before that day I was thinking that only at close distance is unsafe to fly. As to the GPS problem I have data from FLYTREX Core. The number of sats was from 10 to 11. The distance between the controller and Phantom was about 200 m. After first stage of the "flyaway" the RTH mode lasted 1 or 2 sec. In the second stage the speed reached 54 kmph in a sec. Its not the malfunction of the controller if so it would cause RTH mode not "flyaway". I am sure that beams from one directional antenna mounted on BTS strictly to the nearest one even at long distance can interrupt radio signal between quadrocopter and controller. Btw its easy to find such beams in rular areas but in urban ones its almost impossible.
     
  8. Exsniperex

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    Here are sets of pics showing the process of flyaway:
     

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