DJi Phantom Advanced (rocking on descent)

[Mr.Spock]

Hello, i have been browsing here since i got my P3A a few days ago, very useful information. Today i come to you with a slight problem i am experiencing:

On fast, or even mid way throttled descents my P3A rocks diagonally, never side to side but horizontally from each prop, & not on all 4 props just 2 horizontally across from each other, kind of like a wobble, it never gets to the point where it gets so out of control it moves to the left or right more then a foot, but its still kinda scary. I am wondering, does it have something to do with an improper calibration, like IMU or compass, or do i maybe have a defective unit? Other than this slight problem, fly's perfectly! I am still within my 30 days of purchase time frame & i got it from Amazon so its hassle free returns.

Any advice is welcome, thanks!

Also, i was wondering, i got my P3A September 30th & i looked @ the comparison picture on how to find out which motors are the updated & which old, & the ones with the flat bottoms are actually the new ones, labeled 2312A, right?

If u are a few meeters from the ground then your IMU needs recalibration.

 

[brianb87]

Same issue here, just started noticing this with in the last week.

 

[Garrie]

Nice company you keep. . .
Thanks for clarifying that "without". I was thinking, Oh man, that's the largest gimbal guard I ever have seen. ;-)

RedHotPoker

Plenty more where it came from. We fly very often in Singapore. I belong to this group called universal drone Singapore

Check out our battery decal given to us free!

Some pics of us relaxing by marina bay in Singapore

And a picture of me with my drone. And you can see the pretty large gimbal guard

 

[RedHotPoker]

@Garrie,
That's just ultra cool. Very pleasing to see the comraderie and your obvious passion for this grand hobby.
Thanks for sharing your pics and fun times with us all. ALL Very nice.
I know the feeling, having joined MAAC and our local ERCHA club.
(Model Aeronautics Association Of Canada,
Edmonton Radio Controlled Helicopter Association)

RedHotPoker

 

[Meta4]

Great info. Too many noobs are unaware of the problems with fast vertical descents.

That's old history. There was a problem with old quadcopters but DJI designers have done a good job with the P3.
They were able to increase the descent speed 50% over the P2 because of the offset props.
The combination works a treat and no reports of P3 VRS problems have come to light.

 

[RedHotPoker]

Mine doesn't shimmy or shake. And I do sometimes bring her in hard.
But it's more fun, doing a practiced, calculated landing, with routine.
The corkscrew is an awesome pattern to practice. ;-)

I have slowly grown, to dislike dive bombing.
Each to his own devices, though. As they say.

RedHotPoker

 

[JKDSensei]

I come down full throttle from any altitude all the time, never any rocking, its actually fun to watch the IMU and GPS fight to keep it stable. I have been flying for some 20+ years though and I keep my trigger finger ready on the sticks in case I need to take over. It's truly amazing the tech that is in these little quads. I have probably flown around 1,000 flights by now and every single one was full speed down until about 20' above the ground, not one single issue even in winds.

Although I agree the slight forward or for that matter right left or back approach while landing will make it smoother, if you are flying in tight quarters like I usually am (high rises, trees, power lines, etc) you usually don't have the luxury of anything except straight down.

If your bird is rocking severely on a full speed descent you may want to check the balance of your props, do a compass and IMU calibration, and calibrate your transmitter sticks, it sounds like something is slightly off.

Herein, I don't think calibration has much to do with it.
It really has more to do with the propellers stalling.
Prop stalling is more likely in no wind conditions during rapid descent.
Also, greater weight and greater thrust both increase the chance of VRS and propeller stalls.

Seems you have an ideal combination of factors that helps avoid prop stalling more so than others.

One last thing, you've "never" done a slow descent in 1000+ flights? "Full speed down until 20' on every single one"? Why?

 

[herein2014]

Herein, I don't think calibration has much to do with it.
It really has more to do with the propellers stalling.
Prop stalling is more likely in no wind conditions during rapid descent.
Also, greater weight and greater thrust both increase the chance of VRS and propeller stalls.

Seems you have an ideal combination of factors that helps avoid prop stalling more so than others.

One last thing, you've "never" done a slow descent in 1000+ flights? "Full speed down until 20' on every single one"? Why?

Ok maybe never is a slight exaggeration, but for me I can do 2-3 jobs on a single battery, the only way to pull that off is to minimize the time in the air. On a good day I can get up in the air, shoot the property and be back on the ground in under 3 mins. That means full speed to every angle, quick snapshot, on to the next, then down as fast as possible.

When I'm on vacation and flying just for fun its a different story but that's rare, too few, and too far in between.

I came down full speed pretty much every time with my P2 and now my P3, never had rocking. I did buy eight sets of props with each Phantom and spent hours finding the perfect combination of props to eliminate jello prior to using it in the field. I mark each prop because each propeller mates to the flight motors slightly better or worse than the other. But other than that, I did not do anything special and never any rocking on the way down.

 

[Meta4]

It really has more to do with the propellers stalling.
Prop stalling is more likely in no wind conditions during rapid descent.
Also, greater weight and greater thrust both increase the chance of VRS and propeller stalls.

Seems you have an ideal combination of factors that helps avoid prop stalling more so than others.

I've tested several times from quite high in perfectly still air.
Full speed down has never shown any indication of VRS.
What you've described is applicable to the P2 series in the early days when it was possible to descend at 6 metres/sec.
Because some people were unable to self regulate their descents and were crashing, DJI reduced descent speed to 4 m/s and then a snail's pace 2 m/s.
This prevented VRS crashes for the P2 series.
With the improved design of the P3, DJI increased the descent speed 50% to 3 m/s and I've never seen any reported VRS incidents for the P3.
But the myth persists.
You can come down slowly, zigging and zagging - but it isn't necessary.

 

[JKDSensei]

Roger that. Sometimes I get into discussions and forget they are specific to certain Phantoms.
Good info.

 

[CONTROL FREQ]

Mine won't wobble on descent but it does wobble sometimes when going forward at full throttle. The camera will wobble (pretty badly sometimes) until i stop thrusting forward. Then i'll slowly go forward again until full throttle and then it'll be ok. Not sure what is causing this.

Anyone have a clue?

Thanks.

 

[RedHotPoker]

Perhaps you'll need to recalibrate the unit, IUC, Gimbal, do the works.
I can't imagine really, what else would cause that?
Are you taking off, from as flat as can be, area?
I know from experience that the gimbal does a minor calibration, every time you turn it on. So before you take off, check to see that it is square with the ground or what ever you have it resting upon.

Sorry that I can't be of any more help, than those regular suggestions.

Good luck, I do hope that you can find a fix, soon.

RedHotPoker

 

[CONTROL FREQ]

i always take off on pretty level ground.

yes, maybe i'll try calibrating everything again.

thanks RHP.

 

[RedHotPoker]

Unless it's a factory defect, we need to try and pin it down, go through all the normal routines, sometimes several times for it to stick.
Be sure to do a cold IMU calibration, and find a counter top or something that you know completely level. And let the gimbal realign its calibration from that. You can do it twice if you feel the need.
There aren't too many things else to try doing, that I can think of right now. If I do. . . Let you know.
Hate to see you send it in for service, to also lose 2 months of use.

RedHotPoker

 

[Jeriami]

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RedHotPoker

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I also noticed recently, that while moving forward full speed (usually about 20 MPH) that the phantom actually moves 20-50 degrees to the right as well, keep in mind the right stick is perfectly straight, it has happened several times now & i am noticing it more frequently with every flight, little to no wind! Also, during full speed & 75% speed descents i am still getting a wobble! Also, doing full IMU calibration & compass & gimble every 2 flights, i do these calibrations just to be safe, i never get any compass or IMU or otherwise any warnings at all. I am only 2 weeks in owning my phantom, so i ask you, should i return it & hope for the best with the new unit? I purchased from amazon so they would accept my return with open arms if i explained the issues i am having. Please advise, as i would like to return ASAP before getting closer to the 30 day mark!

 

[RedHotPoker]

With our standard RC radios we have trim buttons to correct that sort of irregular flight. With the Phantom 3 technology onboard, it should not be a problem that needs correction. So yes, there is Definately something amiss. Perhaps the compass is not responding correctly to the input it is receiving? That's only a guess.

If returning it is a reasonable procedure, if it were me, I would suggest go ahead and do that & exchange it. You will be totally happy with a bird that will fly correctly for you. It's a marvelous investment, so be sure to get one that works. ;-)

RedHotPoker

 

[Garrie]

I will be changing my carbon fibre gimbal guard to a much thinner version soon. Will test out if it still wobbles when doing a 100% descent. If it does I might post a video and see if it's similar to the type of wobble you are experiencing.

 

[Albert R.]

Careful with rapid descents. Even though the P3 has slightly angled props to prevent this be careful.
Quadcopter Flight School: Vortex Ring State (The Wobble of Death)

 

[captain-marvel]

I get some wobble from time to time in descent but I've also seen it badly on "learner" quads and have figured out how to escape it.

The p3's are very powerful. If you start wobbling with p3, a lot of times you can throttle up and pull out of it which is usually not the case on less powerful quads.

The only time I've seen a p3 suffer badly for VRS is with prop guards and even then it's NOTHING compared to cheap quads.

Full throttle with forward thrust and you'll be just fine.

 

[Jeriami]

I will be changing my carbon fibre gimbal guard to a much thinner version soon. Will test out if it still wobbles when doing a 100% descent. If it does I might post a video and see if it's similar to the type of wobble you are experiencing.

I removed some prop guards & figured out that was my problem. Did you ever find a solution to your issue?