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Prop Wash
1608 12 2015-3-21
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trrdesign
lvl.3

United States
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Was flying today with my vision2 and was showing a friend all about the Phantom.  Last flight, went up around 60', was manuevering around and all of a sudden the phantom started to wobble back and forth.  It then came down prety quickly rocking back and forth.  Hit the ground, popped off the comapass cover, but that was it.  Cleaned it up and did a quick test flight after and everythign seemed ok.  Was using removable prop guards and had the carbon fiber props.

So some questions:
Does that sound like the prop wash problem?
If this does occur, is there anything you can do to try and get out of it?  I was talking with my friend and not paying 100% attention, so did not try to power up.
This was the first set of flights with the carbon props and removable guards together.  Guards are really sturdy.  Is the combination of the two, more apt to create the prop wash?
Phantom is fine.  

2015-3-21
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nrgwise
First Officer

United States
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Some say prop guards are a possible contributor the problem.  But if you weren't paying attention it would be hard to judge by your observations.  Were you descending at all?  And if so, straight down?  Any video of the flight?  
2015-3-21
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JATO
Second Officer

United States
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From what I've read pure CF props and the Phantom don't mix. I have also seen some posts about prop guards causing issues. It does sound like your bird doesn't like the combo.

I would lose the CFPs and maybe when you feel comfortable flying the prop guards.
2015-3-21
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gnixon2015
First Officer

United States
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what you had was VRS.  the prop guards, combined with straight down descent, combined with the prop wash dynamics of CF props versus stock props, caused VRS for you.  getting out of it:  try and move laterally slowly to get out from the wash, DO NOT try to increase throttle, while that is natural, it can amplify the problem.  ive had it happen twice and both times i simply stopped all stick movement, going back to center, and it got itself under control.  the second time was on a windy day and it did struggle.  and yes, the combination is a big factor, but wind and flight profile are also factors.  dont use the guards with CF props in high wind.  and when using them both in low wind conditions, always descend by moving laterally (my rule of thumb is move out more than the rate of descent... 1ft down, 2ft out, etc, making it a fairly flat slope.  takes much longer to get down but i rarely get wobble now).
2015-3-21
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yorlik
lvl.4

United States
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I know a lot of folks say stay away from prop guards, and that's great if you can.  I live in a log home buried in the middle of 80 acres of 120+ foot trees with max opening of approx 40x40'   It is not an option for me.  That said, in 2 months of almost daily flights, I can say it is a TAD more unstable at times than the 1 mo flight time before putting them on, but absolute no issue of vrs from 600' down.  I bought 16 replacement blades that first month!  just keep that horizontal slight motion happening on way down.  My prop guards will not come off , even when I grow up and get better at it.
2015-3-22
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trrdesign
lvl.3

United States
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Thanks all.  I'm going back to the 9450 props.  Just for info, I was about 60' up and was just doing a turn to the right and then a quick turn to the left to show my friend something.  It looked like it dipped when doing so and then got into the back and forth.  I believe I hit the throttle up, since that is 2nd nature for me whenever I am concerned.

No video, I had jsut finished on previous flight and was just showing some maneuvers. I had shown him the fail-safe and had it come back to me.  i then took control and flew out about 20'
2015-3-22
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jdlucas
lvl.2

United States
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trrdesign@cox.n Posted at 2015-3-23 08:43
Thanks all.  I'm going back to the 9450 props.  Just for info, I was about 60' up and was just doing ...

FWIW, I've had this happen once.  I was flying in 27*F temps with a halting mist.  While I was attempting to land it began wobbling at about 60 ft and long story short I tried to move it around to get it under control but crashed.  I might add I was not coming staight down, I was moving it around some because I was aware of this problem.

I was also using prop guards with quick snap on attachments.  Also I was using a string as it made them sturdy as without the string they were loose.  Also, they're is the possibility the bird was collecting ice in this mist at 27 degrees.

I haven't flew with prop guards since but I think they have a place.  If I use mine again, they will be screwed on as intended.  I'll never use the quick attachments again or fly in misty cold conditions again"
2015-3-23
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jdlucas
lvl.2

United States
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trrdesign@cox.n Posted at 2015-3-23 08:43
Thanks all.  I'm going back to the 9450 props.  Just for info, I was about 60' up and was just doing ...

FWIW, I've had this happen once.  I was flying in 27*F temps with a wet mist.  While I was attempting to land it began wobbling at about 60 ft and long story short I tried to move it around to get it under control but crashed.  I might add I was not coming staight down, I was moving it around some because I was aware of this problem.

I was also using prop guards with quick snap on attachments.  Also I was using a string as it made them sturdy as without the string they were loose.  Also, there is the possibility the bird was collecting ice in this mist at 27 degrees.

I haven't flew with prop guards since but I think they have a place.  If I use mine again, they will be screwed on as intended.  I'll never use the quick attachments again or fly in misty cold conditions again"
2015-3-23
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adrianjacobs
lvl.4

United Kingdom
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I have experienced what I would call "slight wobbles" which last less than a second while descending vertically,  I avoid it by coming down in a spiral or at a slight angle.  my concern with doing this is that the sticks might get a bit close to the CSC positions but if I don't use any yaw, the machine is moving away from where I want it to land (assuming I'm already vertically above where I want to land).
2015-3-23
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Swerve
lvl.4

United Kingdom
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I would be interested to know if anyone has suffered VRS (vortex ring state caused by descending through your prop wash) without prop guards. Always seems to happen only where these guards are installed.
I have never used prop guards but still, as a precaution, I try not to descend vertically if possible.
2015-3-23
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gnixon2015
First Officer

United States
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swerve, ive had this happen to me without prop guards also.  they arent the only factor.  if you yaw while descending (or come down faster than you move laterally) and/or have high winds and/or have a heavier bird (add ons, trackers, mods, etc) those factors can still cause VRS without guards.  ive had it occur with both and i fly with both frequently and my guards only seem to heavily influence this situation as the wind speeds increase.
2015-3-23
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Swerve
lvl.4

United Kingdom
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gnixon2015 Posted at 2015-3-23 20:06
swerve, ive had this happen to me without prop guards also.  they arent the only factor.  if you yaw ...

Were you able to recover it?
2015-3-23
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gnixon2015
First Officer

United States
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i was able to recover all of these except one.  one time i was too low and the VRS caused a rapid loss of altitude (about 15ft in a second or two) and i was only 30ft off the ground.  i ended up landing in a small tree and toppling to the ground.  no damage.  the other 2 or 3 times it has happaned to me i was able to recover.  coincidentally, the one i couldnt recover did NOT have guards on and the ones that i did recover, some were without guards and some were with.
2015-3-23
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