Vision 2 fall as a penny drop ...

[Psioui]

Hi there

I bought my Vision 2 as soon as they released them back in November, if I remember well !

I had 1 or 2 crashes at the beginning, but that was about it !

For the last few days, I was in Joshua Tree park in California, about 3000ft above sea level.

Everything was ok, no issue at all, flying here and there.
This happens twice, pretty much the same thing happened:
You know when you bring down the Vision 2 at full speed, it doesn't go straight down (flat)
It look more like when you drop a penny, kind of rotating, you know what I mean :?:

So it started to come down, but never stopped, I tried to push the joystick to raise it, try to go foward, backward everything,
nothing it was almost a free fall.

I've never lost the FPV or the signal between the Vision 2 and the remote.

Anyone has an idea ?

Thanks for your help !

 

[Pull_Up]

http://en.wikipedia.org/wiki/Vortex_ring_state

If you were heading straight down for a prolonged time that might be what happened.

When descending it help to move horizontally at the same time, to stay out of the turbulence of your own propwash. If you need to keep it more or less over a similar location whilst descending you can always give a little roll and yaw together to bring it down in a spiralling way. You may have got to the point where you had lost lift completely, hence your control inputs having no effect.

 

[havasuphoto]

Vortex Ring State is also called "settling with power". Basically you are descending into your own down wash. And, it's at that point, you're in trouble. IF you add more power to reduce or stop the descent, the aircraft will actually descend faster, as your down wash is now actually rotating above the aircraft, and pushing it down.

This is why real helicopters rarely descend vertically. The recovery for this, is to reduce power, and fly in any direction-preferable into the wind. The controls will be slow to respond, and the rate of descent can be very fast. You are more likely to get into Settling With Power at higher altitudes, and, at heavier weights-hot days)-as that requires more power to hover, which produces more down wash.
You can also get into this condition if you descend backwards, on a windy day-into your own down wash.

I see a lot of people are not familiar with helicopter/quad aerodynamics. But this one, will cause you to crash, if you're not aware.
The Quads can climb vertically very quickly. But, descending requires a bit of thought. It's best if you fly forward(away from your down wash), and keep your rate of descent at a fairly slow rate. Fly circles around the spot you want to descend too. Or, just keep moving forward as you descend. My rule of thumb is; it should take me twice as long to descend, as it did to climb up. So, I factor that into my flight time, when going up really high.

You will know you are in Settling with Power, when the aircraft starts to yaw back and fourth, and tilt, rapidly. You can even hear the engines, if you're in GPS mode, straining to control the attitude of the aircraft. Forward stick...and fly out of it.

 

[MrTommy]

Wow! Great advice! I'll keep this in mind. I've been a big helicopter fan since the days of the black & white TV program "Whirlybirds" back in the 50's. I've watched many Vietnam era pilot training films (that I bought from Sporty's Flying Shop"), but never heard of this problem. It's kinda like how scuba divers avoid going up faster than their bubbles, only in reverse. Cool. You may have saved MY Phantom, and it hasn't even arrived yet!

 

[havasuphoto]

Wow! Great advice! I'll keep this in mind. I've been a big helicopter fan since the days of the black & white TV program "Whirlybirds" back in the 50's. I've watched many Vietnam era pilot training films (that I bought from Sporty's Flying Shop"), but never heard of this problem. It's kinda like how scuba divers avoid going up faster than their bubbles, only in reverse. Cool. You may have saved MY Phantom, and it hasn't even arrived yet!

No problem. I spent 23 years flying helicopters, was also an Instructor and Check Airman.
Quad rotors produce much more down wash, than a single rotor system-so they are much more susceptible to SWP, than other rotor craft.
I also flew the Chinook-Tandem Rotor. That big pig loved to settle with power. When I was logging, we were always moving with the load.....rarely did we descend much, and when we did, we were usually "sliding" sideways into the log landing-punched off the load, and returned up the hill-all in one motion.

Try to visualize where your down wash is...and learn to fly to avoid getting into it.

I noticed this phenomenon on one of my first Phantom flights-and immediately recognized it for what it was, and added forward control movement, and it flew right out of it. I normally don't descend at more than 2m/sec(I have iOSD and FPV-so I have that information available). And, I usually maintain about 4m/sec forward/sideward/rearward, while descending. Those are my "target" speeds. I spend much more time concentrating on flying, while descending-and always have a plan on how I'm going to come down. Usually, I just fly a Box.......forward....left...forward....right, forward, left..you get the idea.


One more thing; you will notice on some TV shows, they are using the bigger quads. You'll also notice that their "hero shots" are shot while they are climbing, not descending. If you see a shot where they are descending, the clip has actually been reversed.......little secret I found out about.

 

[Pull_Up]

One more thing; you will notice on some TV shows, they are using the bigger quads. You'll also notice that their "hero shots" are shot while they are climbing, not descending. If you see a shot where they are descending, the clip has actually been reversed.......little secret I found out about.

Now that's a nugget right there!

 

[havasuphoto]

One more thing; you will notice on some TV shows, they are using the bigger quads. You'll also notice that their "hero shots" are shot while they are climbing, not descending. If you see a shot where they are descending, the clip has actually been reversed.......little secret I found out about.

Now that's a nugget right there!

shh!! Don't tell anyone

 

[Psioui]

Thank you very, very, very much everyone ! I<ll keep an eye on your advise !

 

[CouesWhitetail]

Thanks Havasuphoto! I am new to quadcopters and have noticed that my phantom 2 has some trouble when I descend straight down quickly. So far the unit seems to compensate for my inexperience But now I know better and will plan for slower, not so linear descents.

 

[CouesWhitetail]

Havasuphoto, can you tell me more about how to fly safely when I am near large cliffs? I hear that updrafts and downdrafts can be strong around cliffs, but how do I know before I am in them? Any chance to avoid them?

 

[shortyuk]

brilliant advice havusaphoto, i travel in helicopters alot with work as i work offshore, and the full size helicopters also suffer this problem as you have said, cheers

 

[havasuphoto]

Havasuphoto, can you tell me more about how to fly safely when I am near large cliffs? I hear that updrafts and downdrafts can be strong around cliffs, but how do I know before I am in them? Any chance to avoid them?

Yea...tilt the camera down, and fly much higher above the cliffs. IF, it's a windy day-don't even attempt it. You're likely to enter a "rotor", a spiraling down wash of air, that will exceed your aircraft's capabilities to fly out of it.

Another method, is to start at the bottom of the cliff, and climb to the top with your aircraft. Again-on a calm day. You can reverse your footage in post processing for a different effect.

Try to visualize the mountains/hills/cliffs as rocks in a creek, with the air being the water. This will help you determine where the updrafts and downdrafts are.
Also, avoid flying in very steeply mountainous terrain when it's windy. The turbulence will be invisible, but can disrupt the aircraft enough that the video will be unusable.

Also-you can use the wind to your advantage. You need to be in Atti mode.....start upwind from your subject, and let the wind blow the aircraft downwind over your subject....uses less power that way.
Same with updrafts-free lift. But-you must be in Atti mode. When in an updraft, if you desire to climb, let the aircraft rise up, reduce the throttle-but no less than a minimum of 10%.

Wind, and updrafts can help you save on battery power......

 

[CouesWhitetail]

Thank you for the advice, that's great information.

 

[CouesWhitetail]

Havasuphoto,

your advice about how to handle the settling with power situation saved me today! I thought I was descending slowly enough and moving around so not descending into my wash, but I must not have been doing it quite right and some wind came through and made my phantom start falling.....luckily since I have read your advice on how to get out of this, I immediately stopped giving left stick and used right to move out of path. It recovered quite quickly, however with many trees around me in a tight circle it was a challenge to fly out of it and yet not hit branches. Anyway, I was so relieved that I was able to execute the "fix" to the falling out of the sky.

THANK YOU!

 

[havasuphoto]

Havasuphoto,

your advice about how to handle the settling with power situation saved me today! I thought I was descending slowly enough and moving around so not descending into my wash, but I must not have been doing it quite right and some wind came through and made my phantom start falling.....luckily since I have read your advice on how to get out of this, I immediately stopped giving left stick and used right to move out of path. It recovered quite quickly, however with many trees around me in a tight circle it was a challenge to fly out of it and yet not hit branches. Anyway, I was so relieved that I was able to execute the "fix" to the falling out of the sky.

THANK YOU!

No problem, you're welcome. I still get into, even Today...but just flying out of it is the simplest way.
Also-plan your descent if you plan on going high. It takes some room to go forward/backwards, or whichever way you're going to fly, just to avoid your down wash.
It should take you at least twice as long to descend, as it did to climb-you need to descend that slowly......just a rule of thumb.

 

[fxmodels]

My experience with a prototype quad we built in our research project was that as long as you had some forward motion while descending the "settling with power" instability problems could be minimized. Further we noticed that orientation of the quad was very important because if you are flying in a + configuration then the forward motor will dissipate its propwash against the body of the quad and the rear motor will be subject to wake turbulence from the body but its liveable. The X configuration though allows the propwash of both forward motors to affect the rear motors directly depending on forward speed.
If you want to fly in either orientation my personal experience is to use slow forward motion while descending and then either orientation works equally well.. But without knowing wind speed aloft you DONT know how much forward speed to apply unless you have enough altitude to experiment for 3-4 seconds to figure it out.
I am just offering what we have found. NOT at all trying to be a know it all ...
Thanks..
Marc

 

[duckdogs007]

Wish I had heeded this advice before my costly crash! I did the same thing.....decended too quickly (straight) down...causing the Phantom to wobble back and forth wrecklessly...actually seemed to just "fall" actually, out of control for about 50 feet or so...thankfully it landed in the grass...but it still broke my gimbal on the Vision2 camera... :evil:

 

[Kelso Kubat]

we just flew right through his jet wash!!!
goose~!
goose i can't control it... i can't control it!!!!

 

[adelaar]

Great advice havasuphoto! I didn't even know this thing existed ( kind off stupid of me )
No accidents happened yet. Tomorrow I have to film above a big crowd.. So if i don't descent above them, only near me ( the landing site ), this problem will not occur?

Thanks!

 

[domdoha]

Thanks for info and advice...