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Phantom + Lightbridge - Freefall

Discussion in 'Phantom 2 Discussion' started by DavidN, Sep 14, 2014.

  1. DavidN

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    I have a Phantom 2 with Lightbridge and a H3-3d. Default Gains except as you suggested ATTI is at 120. Compass is correctly adjusted. All firmware is up to date. RC is a Taranis.

    I take the Phantom up to 75 or 100 feet with GPS (no less than 8 satellites) hoover for short while then begin to descend straight down at a constant moderately slow speed by holding the throttle in a steady position a little below midpoint. At some point in the descent the drone will essentially go into a free fall. Sometimes if I throw the throttle all the way up and I will get the drone to slow down and begin an ascent. I have swapped the FC from a Phantom Vision Plus thinking I had a FC issue. Same pattern has happened. Issue has also happened with different batteries. Does not seem like an antennae problem as I have replicated the issue with the Phantom in several different orientations. Thank goodness for some very dense unmowed grass as a couple of times the Phantom has dropped fifteen or twenty feet to the ground.

    I am not sure where to go from here.
     
  2. damoncooper

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  3. HarryT

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    Agreed - a classic description of VRS.

    Don't descend vertically - fly forward (or in any direction you fancy, in fact) while you're descending. Ever watch a real helicopter land? They never, ever, descend vertically; they fly down and forward, pull up into a hover just above the ground, and set down from the hover.
     
  4. DavidN

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    Thanks for the help. OK after reading the info on VRS in the link I do believe this is what I was experiencing. Let me add another piece to my story. The reason I was doing these vertical descents was I was trying to replicate something else I have experienced with this Phantom 2 but not with my slightly lower weight Phantom Vision. I had on a couple of occasions been where the Phantom 2 would fly fine in any horizontal or vertical movement but after 7 or 8 minutes of flying would ascend only at very slow speed or not at all. Even with the throttle all the way up. Sometimes even descending with the throttle all the way up. It was these uncontrolled but slow descents that got me doing the vertical drops that I now know were causing VRS. But what was going on in the other case of the less than normal throttle response. The Phantom Vision has none of these issues of sub par throttle response.

    I live at 8000 feet and I have a Lightbridge unit attached so some added weight. That might explain the low throttle response but what would explain the throttle sometimes being fully able to lift the Phantom 2 vertically at a nice clip and the next minute full up throttle and the drone is barely rising or even sinking. I stumbled in VRS while trying to figure out what was going on with the occasional throttle issue. Now I need to get an understanding of this throttle issue. Is the Phantom 2 + Lightbridge + H3-3d + GoPro + 8000 feet a weight and thin air combination part of this issue. But why then is most of the time vertical lift is just fine. Other times definitely not so much. I could try the new 9450 prop. But again why the current variability in ascending power?
     
  5. sar104

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    That is strange behavior. I have a P2 with LB and I have not seen those issues at 7500 ft. Are you using prop guards?
     
  6. HarryT

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    Are you using DJI stock props?
     
  7. Petereesha

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    do the back lights flash red during ascent?
     
  8. DavidN

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    No prop guards.

    Stock props that were shipped with the Phantom

    No the rear LEDs are not flashing red.
     
  9. DBeard

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    :shock: I've noticed that RTH flies directly down.
    What to do about that?
     
  10. sar104

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    Do you happen to know the actual weight of your P2?
     
  11. RIDETOEAT

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    Someone may correct me but it sounds like heavy and high and as battery voltage drops performance suffers. As a result of being heavy and at high altitude it is more obvious.
     
  12. sar104

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    It could be that, but I have a nominally similar configuration at a similar elevation and I don't have that problem. We really need to know the actual weight of the aircraft for comparison.
     
  13. DavidN

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    I do not. It is all stock. Phantom 2, Lightbridge, H3-3d, GoPro. Removed the 2.4 receiver to shave a few grams.
     
  14. Haze

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    Pretty Sure its VRS like 99.9%. What Firmware u on? 3.06 should stop that. but it slows you down too. Helicopters or quads are susceptible to VRS going straight down, thats why you don't do it or don't do it fast but even slow its a possibility. also when in VRS you NEVER hit the throttle EVER.. you use side stick. Throttle will make it worse and probably why u have hit ground a few times. SIDE STICK AND SLIDE OUT OF VRS. read about vrs then fly.
     
  15. DavidN

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    If you go back to the fourth post in this thread, you will see that yes VRS is probably an issue in the freefall. In the fourth posting though, I responded with additional information and the issue that got me to be doing the descents that triggered VRS occurring. Basically I am occasionally not able get the Phaontom to ascend even when VRS is not occurring. Sometimes from a hover or slowly ascending, giving full throttle and the drone will barely rise or even slowly descend. I think I explained better in the fourth post of the thread. Thanks much.
     
  16. Petereesha

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    This is what I'm thinking as I have had a similar issue with a P2V with RP gimbal.
     
  17. sar104

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    Sounds like it is identical to mine and operating at a similar elevation, so that suggests that the behavior indicates a problem somewhere. Battery contacts?