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High speed descents

Discussion in 'Phantom 2 Vision Discussion' started by pault, Feb 17, 2014.

  1. pault

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    This is a just in case I need to do it type of post.

    I have read numerous posts about how to descend properly and I understand the need to avoid Settling with power so now when I descend I am careful to go down slowly but want to be prepared to get down fast. The battery alarm on my phone is very quiet and it is easy to get carried away and not notice the power drop from under 50‰.

    Am I right in thinking it is good to descend with motion into the direction of the wind ? Gut feeling says that the propwash will be blown away with the wind and the P2V will be going down into undisturbed air. Some people have recommended descending in a box pattern but presumably one of the legs will be with the wind.

    The second question is how much downward motion to apply on the stick. At the moment I descend in stages - a few seconds of half way between center and bottom - level off and repeat but as I said in the beginning of this post this would not be a feasible proposition in the case of an urgent landing.

    I repeat, I know this has been discussed many times and I know some people get pi$$ed off by the same posts coming up again & again - but I have read a post which says it is not good to reverse into a tail wind which got me thinking I might be wrong.
     
  2. Pull_Up

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    You can descend as fast as you want if you give it some lateral movement at the same time (or indeed set up a spiral). Personally if I had to get down quick but not in an emergency (if imminent light aircraft collision risk for example then I'd just CSC and let it plummet) I'd drop throttle to just above the stop and shove the right stick fully in any direction. The combination of reduced lift with lateral motion should keep you out of wash and enable you to take control again by releasing throttle stick first then attitude stick after a second or two (assuming GPS mode and enough height above the ground).

    Take your aircraft up to a safe height and practice what works for you. Heading into wind would tend to move the prop wash, but in a tricky situation you may not have the luxury of repositioning. Keep the aircraft moving sideways and you'll be ok.
     
  3. pault

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    Good idea to practice - I presume that if I do get into a Settling with power situation then it will correct itself if I can resist the urge to apply more throttle .....

    As regards just moving sideways, I presume if you have a crosswind then it would not be good to descend with it .....

    Edit: I am a bit nervous trying to induce a Settling with power situation even with altitude as I have just watched a video of P2 plummeting and it looks like he had a couple of hundred feet when it started .....
     
  4. Pull_Up

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    No, don't induce the situation. Practice rapid descent trying not to get into it in the first place I meant. If you are in a vortex ring state then the IMU won't rescue you. The practice I meant was descending with lateral movement or with spiralling. If you do get into the state, use the right stick to move out of the column you are in before attempting to recover hover with power.
     
  5. iResq

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    Agreed that rapid decent with lateral movement is a good skill to practice.

    Sent from my DROID RAZR using Tapatalk
     
  6. LandYachtMedia

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    I did some testing on mine (P2) and have found that you can descend a bit faster with stability than normal if you spin the craft at the same time. Forward flight while descending is definitely better.

    Descending while spinning will get you down faster than coming straight down.
     
  7. outlaw704

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    Descending into the wind is an excellent idea. If you envision a vertical cylinder through your P2V as a no-fly zone you should be safe.

    On a windy day that cylinder will tip over slightly with the wind (downwind), so anything you do to maneuver out of it, like flying into the wind will be beneficial in a rapid descent.

    If your flying area is compressed, come down quick while moving forward into the wind - when you run out of airspace make a quick horizontal run downwind to gain more flying room - and then start your (almost) vertical descent into the wind again.

    Repeat as necessary. The maneuver will look like a series of large stair steps. I practiced this the other day in the size of a football field (apologies: soccer pitch?) and got comfortable with a very rapid, yet controlled descent in a "small" space. The practice session was also very beneficial to help me with wind awareness.

    outlaw704
    Austin, Texas, USA
     
  8. pault

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    I have started to switch into ATTI briefly before starting the descent so I can confirm the wind direction aloft and then powering forwards and down into it.
     
  9. milezone

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    Maybe I am so new I am not understanding the actual issue here, but when I decend I sometimes just go down full throttle and have yet to have an issue going down fast? I dont go forward or anything like that, I just hit it and go down fast as I like? Thinking maybe this is not advisable now, but no sure why?
     
  10. Pull_Up

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    You can get caught out in vortex ring state, also known as settling with power: http://en.wikipedia.org/wiki/Vortex_ring_state

    It's basically a situation where the rotors are effectively stalled. Adding power has either no effect or makes things worse. Descending into your own wash also makes for a bumpy ride!
     
  11. Ozzyguy

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    I wouldn't over think it. Like anything else you need to train in a variety of conditions.
     
  12. outlaw704

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    Excellent idea !
     
  13. Ozzyguy

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    Having said the I have had the loss of lift that pull up is talking about. I was descending straight down on a day with no wind. Very fast loss of altitude. Quite alarming. No damage done though.
     
  14. iResq

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    Calm air makes it worse. I don't over think it either. I just make it a practice to move lateral and down at the some time. Usually nose in. I'm not sure finding wind direction and making an upwind approach makes that much of a difference (except maybe atti or manual but that's just for straight flight not vortex).

    Sent from my DROID RAZR using Tapatalk
     
  15. GMANNZ

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    learn to do spiral dives full noise ... looks way cool and keeps "vortex of death" at bay ... :cool:
     
  16. Pull_Up

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    (As long as the spiral isn't inverted ;) )
     
  17. LandYachtMedia

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    Once the collective pitch version of the Phantom comes out we should be able to pull that trick off!! :mrgreen:
     
  18. LandYachtMedia

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    You know, I made the collective pitch comment in jest but it looks like someone has actually done it!

    [youtube]http://www.youtube.com/watch?v=TnGhEInTXYc[/youtube]
     
  19. Pull_Up

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    Yeah I've seen that, it's mad! The really clever thing is there's just one motor on the aircraft...
     
  20. duneview

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    I had a crash today.. was defending and the craft started wobbling and plummeted to earth.
    Could this be from defending too fast?