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RTH speed on Vision+ is really slow ???

Discussion in 'General Discussion' started by MadMitch88, Jan 1, 2015.

  1. MadMitch88

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    I was flying my P2 Vision+ a few days ago during an unseasonably warm day here in Northeast Ohio. I was operating in GPS mode with about 10 sats locked and I lost signal about a mile out (I have Sunhans amps and pinwheel antennas on my bird so I can do long distance flights). Sure enough, I flick off the controller power to initiate RTH function. I was able to maintain FPV link so I could see video of the bird turning around and heading back home to my takeoff point on my Vision app.

    However, I noticed the airspeed dropped from around 15-20 MPH down to 2 or 3 MPH during it's RTH flight. There was some slight wind that day, but not more than occasional 15 MPH gusts. I have witnessed at least 25 RTH flights since I bought my Vision+ in July and never seen it slow down this much! It was still about 3,000 ft. out when I noticed battery was down to around 40% so I knew I had to act quick or it was going to auto-land kinda far from my takeoff point in a neighborhood I wasn't familiar with. I flick the S1 switch down to Position 2 so I can regain control of the bird, flick it back into Position 1 so I can have GPS mode and then max. out right stick and notice airspeed increases up to 20 MPH like normal. Luckily, I was able to land and hand-catch with about 12% battery remaining.

    Can a headwind really make an RTH flight practically stall out like this? This could've been disastrous if I was further out when RTH was initiated, or if I lost FPV signal and couldnt see how much battery was remaining. I have the Flytrex Live 2G device but the idea of rummaging around in peoples' backyards looking for my bird doesnt appeal to me much. I suppose I should've kept S1 in ATTI mode when I stopped RTH so I could achieve max. airspeed, right?
     
  2. Buckaye

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    How high was it when it started to come back? I'm wondering if it was trying to get down to the RTH height without causing VRS? I haven't messed with RTH much lately... But it does sound weird that it was slowing down so much... I doubt the occasional gust would mess it up... If it was a constant 15 mph... Maybe. I guess it's possible the wind speed at flight level was constant.

    Oh and Go Browns... Sigh,
     
  3. crash1sttime

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    Quads dont drop to RTH height, if RTH kicks in and your at 400ft, they fly back at that height and then descend, thats why its important to get max altitude if you think your about to lose connection

    Or so im led to believe.

    Not sure why it would slow down though.
     
  4. Buckaye

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    Oh yeah,.. I was thinking the other way around... If you're too low it will raise to RTH height... Disregard with apologies.
     
  5. crash1sttime

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    Dont apologise mate its new years day and no doubt most of us are still hungover :lol:
     
  6. MadMitch88

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    It was around 450 ft. when I lost control signal. Like Crash said, RTH is designed to fly home at the same altitude it loses signal, unless it's under the 20m threshold of above-home point at takeoff. The new updates allow you to specifiy a RTH altitude as well.

    In the previous 25 or so RTH flights I've witnessed, I've seen airspeed drop to around 7 or 8 MPH. Not sure if this was due to a wind gust, or maybe the bird needing to lock on to GPS better.

    BTW, I live in Cleveland but am a diehard Steelers fan. My Daddy raised me right! :p
     
  7. crash1sttime

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    Then maybe the wind was just that much stronger at the height you were flying at, chalk it up to experience.
     
  8. MadMitch88

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    That's one thing I was thinking --- it was kinda gusty at ground level but probably stronger at 400 ft. high.

    There might even be some kind of internal algorithm built into the flight controller where it slows down to a near-hover when it encounters a strong headwind. Maybe trying to avoid a VRS or something.
     
  9. macheung

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    The p2 and likely p2v has different tilt limits at different modes. These will influence max air speed and with wind, ground speed.You said airspeed in your 1st post, but I am assuming that it is actually ground speed if you are reading it off your fpv since phantoms do not have airspeed sensors.

    Manual = no limit! though practical limit near 35-45 degree for level flight depending on weight.
    Atti = pre v3.x 35 degrees , recent 25 deg
    GPS = pre v3.x 25 deg, now 15 deg
    RTH = pre v3.x 15 deg, now 10 deg (I am less sure of the exact values here)

    So you see, if you are coming back against a headwind, RTH can makes almost no progress if the wind is even moderate 10-15 mph. If you still have fpv feed, best to take control ASAP and fly it back in atti mode.