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Strange control problem

Discussion in 'Phantom 2 Vision Discussion' started by enterprise1, Jul 23, 2014.

  1. enterprise1

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    Been flying my PV2 for about 6 months without any control problems. Zero crashes. Moding mostly for FPV and adding after market Tx antenna. This past week I've had 3 hard landings but only chip prop damage. Had to replace 3 props now.

    The loss control only happens during landing with around 30% battery remaining. Take off and flying out to around 3000ft is good no problems. Normally I hand catch my landings so it must be stable. Still have all my fingers. My 2.4ghz craft pinwheel antennas hang below landing gear. The Vision has one 5.8ghz pinwheel attached and the standard antenna. Controlling signal has never been a problem until this week. Now when craft gets within a 100ft away and maybe 20ft high I loose complete control. No screen messages but Vision is actual trying to land but is doing a very hard landing. I am able to turn motors off after crash.

    I've checked all antenna connections and took cover off transmitter to check antenna wire. No help though. Did the same thing on next flight. Change my Nexsus7 app from 1.38 to 1.40 with same result. Didn't expect changing app. would help but getting desperate.

    I do run with 3 sunhan amps. One 1 watt for 5.8ghz with 4.5 turn Helical antenna and Two 2 watt amps with 2 half dome helical antennas for 2.4ghz. This setup has served me well for around 100 flights.

    Something has changed with my equipment but just can't put my finger on it. Anyone have suggestions for problem solving this issue. Any help would be appreciated.
     
  2. John Shaw

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    I certainly don't know for sure, but consider...
    High gain antennas usually have a narrower beam width and alignment of both antennas gets more critical. Is it possible that as you get nearer you are flying out of one or both of the beams. For example if your controller antenna is aimed down for distance do you fly out of the top of its coverage as you get closer? OR As the Phantom approaches is its beam aimed over your head - not at your controller?
    Just food for thought.
     
  3. enterprise1

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    That is a good point John. I don't have a problem taking off just landing. The 5.8ghz antenna on craft is facing different direction during return for landing or 2.4ghz antenna on craft could be blocking control signal. I recently changed position of 2.4ghz antenna on the bird for better wifi signal. Certainly have pilot side antennas pointing almost parallel to ground for low altitude distance flights.

    While replacing damaged props from hard landing I noticed my replacement props are not official DJI props. Bought from Amazon. No DJI lettering. Um no wonder they were so cheap. The props on the craft were the originals until this week.
     
  4. enterprise1

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    Thanks for the reminder dirkclod. Always a chance I forgot something but controller batteries were charged. Had to use a spreadsheet to record battery charging dates or I would forget. lol.

    Today I flew a test run with all new authentic DJI props. Guess what no landing problems. Landed the craft at least 6 times with complete control. My guess is being I had mixed origin props on, it may have been unbalancing the craft at low speed during landing. Like I mentioned above control was not completely lost after hard landing because I could shut the motors off. I do fly with prop guards attached so I must be very careful not to descend to quickly when landing. All of my landing problems started after nicking a prop and installing a new no name prop. Lesson learned I hope. lol.
     
  5. N017RW

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    I'm not sure it's effort well spent to worry about Tx batteries so much.

    The Tx has a battery level warning 'system' built in.

    The supply voltage is regulated down (to ~3.3v or so) so there is no loss of Tx power as the batteries drain.
    Once the battery level drops to within the regulators 'dropout' voltage (typically Vreg + 1.1v) the Tx will warn you.

    I would always encourage others to determine your own best practices but this is one that may be counter intuitive and should not enter into problem solving as it is not likely the cause of loss of control.