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What NOT to do during landing/descent.

Discussion in 'Phantom 2 Discussion' started by Cygan, Apr 27, 2014.

  1. Cygan

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    Hey guys, I did have this post imbedded in another discussion on the general forum but I'm really looking for input on this one as I need to learn what I'm doing wrong. I set down and I tried to figure out what I was doing on those three different occasions and to be honest I think the speed of descent was the culprit here but any input would be really appreciated.

    Here are examples of the three landings where Phantom just stop responding to anything...

    https://www.youtube.com/watch?v=UXP-8Ep ... e=youtu.be

    I noticed that it was always:
    1) with light/moderate wind
    2) Phantom was always facing me
    3) moving forward and down at the same time
    4) always around the same altitude (no idea exactly how high but will know soon as I have iOSD on the way)
    5) battery was about 30/50%

    If this happens again I will consider just getting rid of it and getting another multi-rotor. :(
     
  2. J Dot

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    Location:
    Sarasota, FL. USA!
    Hello,
    Sounds like a VARTICAL GAIN setting!

    Hook to PC assistant
    Look for BASIC TAB, click it
    Look for VERTICAL GAIN
    LOWER GAIN ( if decent too fast ) ( small increments at a time )
    Try to fly , you made be ok, or might want a bit less or more, use your best guess or judgement!
    ( just remember a little goes a long way, small adjustments at a time is best )

    Hope this helps!

    ( HAVE YOU ADDED ANY WEIGHT TO YOUR PHANTOM?
    ie: new gimbal, tracker,ect.?)

    Also, check your props ( for balance, and damage )
    And check all four motors ( bearings ) see if spin freely, not gritty, or tough to spin
    You can pick up on motor, push side-side, ect, make sure each it tight, no slop side-side or up-down!
    ( my friend experienced vortex once with hard landing, it was a bad motor bearing ( front right motor )
    Just a thought, flew fine under power, as he was decending, powering down, the bearing caused the motor to glitch a bit,
    Ultimately causing a crash! ( he said he noticed a weird hum from the motor, when running, other 3 were quiet! $8 fix!
    ( if there is up-down slop In motor, you lost an E clip! )

    Jerry D
    USA
    ( J Dot )
     
  3. Sanababit

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    Its happened to me once, did not hi the ground that hard tough, it started flying again with no problems, besides the tips stated above what i do i go foward at a certain speed and pull down on the stick so i comes down in circles, i dont go straight down anymore, because that is what happens, i did lower vertical gain to about 6 m/s..

    BTW i saw your frustation on the second landing, lol

    Sana
     
  4. ianwood

    ianwood Taco Wrangler
    Staff Member

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  5. QYV

    QYV

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    +1 possible Vorten Ring state... and I didn't realize prop guards increase that potential. Basically don't descend straight down at max rate.
    here's a copy/paste from another thread
    rotary wing aircraft, when descending straight down can descend into their own prop wash (disturbed air) causing loss of lift. if you understand the physics involved, simply giving it lift/thrust doesn't fix it - you NEED to move the other stick ( go forward/backward/left/right ) to get into "good" air and get lift back.

    one thing I didn't see mentioned is that in Firmware version 2 or 3 they put in a "rate limited descent" to help guard against it. They made the max descent rate I believe 3 meters per second which is still enough to bonk pretty hard on landing, but if you're up in the air having that limited rate of descent should avoid a vortex ring state. HELP avoid.. nothing is perfect!

    knowledge is power, this video might help you visualize it
    https://www.youtube.com/watch?v=HrsGM0PzQFo
     
  6. PhotoPilot

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    This happens often and is caused by the have quad basically trying to descend into it's own propwash, Always have momentum is some direction when descending.
    +1 Vortex ring
     
  7. Meluk

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    I think the new firmware has reduced the max rate of descent. Hopefully eradicating the possibility of the dreaded vortex!


    Sent from my iPhone using Tapatalk
     
  8. Ozon8r

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    Happens too often to me but only in GPS mode. If I see it happening and switch quickly to atti I can pull out if it. I think the vortex circle theory is pretty creditable and gps mode just exacerbates the issue trying to over compensate once the death wobble starts.


    Sent from my iPhone using Tapatalk
     
  9. d4ddyo

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    Definitely VRS. When landing I always zig zag down. Note wind direction. descend vertically with as much horizontal movement INTO the wind (the more horizontal movement the better and the faster the decent is possible). When I overshoot my landing area and still have room to land keep altitude and move laterally to give yourself more landing approach and then start descent again INTO the wind. Flying with the wind can counteract your horizontal movement (think running backwards on a treadmill or running up a down escalator) keep doing this zig zag descending into the wind and you will avoid VRS completely.

    That is the problem with VTOL. Helicopter pilots are taught to nose down to gain horizontal airspeed before collective pitch and power.

    theoretically when you hit VRS you should attempt to go into ATT mode (should be Manual mode but most of us can't control a quad in manual) and gain horizontal airspeed before powering up... this is even more difficult with 4 rotors than a single rotor with tail rotor helicopter. Better just avoid as much as possible.
     
  10. riblit

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    Maybe without prop guards but still possible with prop guards. First person experience.
     
  11. ianwood

    ianwood Taco Wrangler
    Staff Member

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    The new firmware limits you to a 3m/s descent which is plenty fast and can still easily result in VRS. You need to move horizontally and if there is wind, you need to move against the wind not with it.

    Recovering from VRS is counterintuitive. Reducing your descent and trying to climb will more often than not only make it worse. You need to punch out sideways before you start to climb out.
     
  12. Cygan

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    WOW! Thank you ALL for contributing! I did print out all the responses and will follow through on those. Sounds like I need to work on my descent then but will also hook up the software and check the settings as well.

    Once again thank you so much for chiming in as I'm totally new to this.

    Regards,
    Marcin