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Some uncommon fail safe questions under WP missions

Discussion in 'General Discussion' started by lesd, May 17, 2015.

  1. lesd

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    So I am interested in waypoint/GS flying up near a tower on a peak that has inside a powerful cold war air raid siren. The tower, which looks like a forest service lookout, now has a few microwave relay dishes on it. The type that the phone companies use. Hence my concerns.
    First question: If the P2 gets jammed by these dishes, will it just hold position in the beam that just caused the jam or did DJI get smarter and when the receiver is jammed it will try to maybe go up another 50 ft to reacquire the signal ?
    Second question: If gps gets lost for any reason, what does the craft do ? Continue current direction some more for a small distance ? Go up some more to see if it can reacquire ? Just sit in the same spot ? Does the Naza auto reject GPS data that is unreasonable ( like 200 miles away in 1 second , etc )
    The tower is too far to reliably hand fly it there, so way points are the method I want to use.
    These type of missions make me nervous ;)
     
  2. Meta4

    Meta4 Moderator
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    It's impossible to say what effects, if any you may notice.
    In the scenario you describe, the Phantom won't climb to search. The design engineers don't know if there are obstacles overhead so they have not programmed it like that.
    If the signal is swamped, the P2 will RTH according to the RTH parameters you have selected.
    IF your Phantom loses GPS satellite lock, it will default to atti mode and just sit there and drift with the breeze (unless you provide control input).
    But how often are you losing sat lock?
    It is very unusual with the Phantom 2s flying in the open.
    Now we're getting into the area where no-one is sure.
     
  3. IrishSights

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    There was a thread a way, way back where a guy confirmed loss of control by flying in and out of the 'beam' from micro wave dishes. I have it on my personal no fly list - risk to high.

    Also in most countries VLOS must be maintained even for GS missions. It wasn't clear from your OP if that was the case of course.

    The other risk factor to consider here too is once the mission is started and if it flys beyond your normal control range (the mission continues regardless) , cancelling the mission mid flight to regain control by flicking gps/atti/gps will not work and you may lose your aircraft.

    Sounds to me like a lot of risks. Based on what you have shared and not knowing the full details of such a proposed flight, If it was me I would find another place to fly.
     
  4. lesd

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    I'm thinking that the microwave dish may knock out the GPS, since GPS signals are also in the Ghz ranges. But if the craft goes into atti mode and drifts, it will likely go out of the 'beam' and regain the GPS signal, I would hope. If it didn't drift right into the dish tower, that is. This site is within VLOS , but it is about 1000 meters away.
    Of course the control signal getting swamped would not cause RTH as it would be on a WP mission where loss of control signal is common, I guess.
     
  5. Scampaboy

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    If you are using the standard iPad/iphone/android ground station app for the P2V+ the GS flight plan is limited to a radius of 500m, you can fly a lot further inside that radius but that is the max distance you can fly in a straight line away from yourself.

    As for the signal interference I wouldn't know I'm sorry although I have made lots of ground station flights in areas of crazy wifi signals and maybe some GPS also though without any problems.

    What height are you looking to fly? if you are flying above obstacles at 100m you should have no problem with GPS signal.
    If you can't access the place to get within 500m or fly manually maybe you shouldn't be flying there anyway? Devils advocate etc.
     
  6. Ezookiel

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    If it loses GPS, then it can't maintain its position because it doesn't know its position anymore. Nor could it go to a position, because it won't know where that is if it doesn't know its own position.
    So my guess is either drift in the wind, or continue in same direction it was last going, and close to a tower, neither of those options would thrill me much.
     
  7. Scampaboy

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    1000m its going to be out of controller range and range of WIFI antenna (if its a vision+) you aren't going to be able to regain control if something bad happens, and also I think at 1000m you are going to have problems seeing it. It seems like a bad idea. Can you not get closer to the object you want to photograph ?
     
  8. Ezookiel

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    I was at 1720m on Saturday, and still had controller signal just fine. I also had solid video, but those weren't with a wifi system, mine is 600mw 5.8ghz.


    Sent from my iPhone using Tapatalk
     
  9. IrishSights

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    1000m is pretty far for maintaining VLOS for the purposes of avoiding collisions and environmental spatial awareness. Where I come from VLOS is regarded by the authorities as 500m, and is required irespectively of whether its a GS mission. Obviously your call. It's always challenging weighing up the possibilities.