Hi all

has anyone noticed that the P4 is very unstable on decent just after 2m.s , I was flying today and coming down in a straight line. is this normal are other people having this issue. I had absolutely no problems with my P3A.

It's called Vortex Ring State and your fortunate that it never happened before if you descend straight down  https://en.wikipedia.org/wiki/Vortex_ring_state.

Thanks for the reply, so this means i can never fly down and record at a good speed. i mean why  does DJI enable that speed on downward flight. DJI has increased the decent speed on the P4

You may or may not experience VRS but I never come straight down just because of the possibility.

Ok as long as it is a normal thing. im just under 20 flights with my p4 and had 115 with my p3A without this issue. Scary stuff, but i will adopt your strategy!

You definitely don't want to crash your P4 because of it. I've had smaller quads fall to the ground wobbling all the way and unable to recover. That's when I learned about VRS.

Flying at the end of battery life is more likely, in my opinion, to get VRS. Your batteries have less juice, therefore less power to recover and keep the bird steady during a descent.

I could be completely wrong, but thats just my experience with my P2 and P4 thus far.

jsparks349@gmai Posted at 2016-8-27 02:49
You definitely don't want to crash your P4 because of it. I've had smaller quads fall to the ground  ...

Your P4 will not tumble and crash during full speed descent.

mobeen.emmamall Posted at 2016-8-27 02:46
Ok as long as it is a normal thing. im just under 20 flights with my p4 and had 115 with my p3A with ...

You are totally fine and the aircraft will not crash.
Have forward momentum while descending and this will not happen.

Yes Ken i understand that. My battery was at about 65% i was decnding at about 1.8ms which is not really fast on a downward shot. The drone starts to shake quiet abit and now makes sense why the motors sound oike they cut off for a second because they actually do. I suppose if you are wrong Ken then someone will test it. Just for clarity you are saying that by decending in a straight line at max you will never lose the drone

mobeen.emmamall Posted at 2016-8-27 05:17
Yes Ken i understand that. My battery was at about 65% i was decnding at about 1.8ms which is not re ...

The max descent rate is 3m/s. at 1.8m/s you shouldn't be getting wobble. And if you descend in a straight line you will not lose the drone, even descending at max descent you will not lose the drone.

Have you ever had a tip over, if so then your props are probably damaged and could be why you are getting wobbles at that slow of a descent.
Change the props and see if it still does it.Another thing that may help is preform a IMU calibration on a flat surface and do not touch it while it's calibration. It cannot have any vibrations either, if you are calibrating on the kitchen table and your large dog runs through the kitchen the redo the IMU calibration.
Also, if you don't reply to a post of mine I will not know you have responded unless I just happen to come across your post.

I've descended straight down at maximum speed from fairly high altitudes lots of times.   And yes..  I've held the left stick fully down the whole way without shutting off the motors .  

I've seen a bit of wobble..  More so when it's windy,  but the craft has never been out of control.  It's never been so bad that the gimbal couldn't compensate.

If descending makes the craft uncontrollable, to the point that the gimbal is reaching it's limits, then I suspect that there is a problem other than vortex ring state.

I noticed this today, was getting a wobble on at full stick decent, never really noticed it this bad in the past, I put it down to the very hot weather, I just checked data and it was defending at 3.5m/s

Snowwolfwarrior Posted at 2016-8-26 17:13
I noticed this today, was getting a right wobble on at full stick decent, never really noticed it th ...

Right wobble?   

Are you experiencing wobble or yaw?  Wobble is when the craft rolls left and right and/or pitches fore and aft.  (Like in a strong wind)

Yaw is changing the direction the craft is facing.  If you're seeing the craft turn to the right, then you're seeing yaw, not wobble.

jwt873@gmail.co Posted at 2016-8-26 23:41
Right wobble?   

Are you experiencing wobble or yaw?  Wobble is when the craft rolls left and rig ...

Sorry for the English language, "A right wobble on" means a bad wobble, :-)

If it's just rotating while descending, it's probably just got a little yaw input from the stick. It's easy to do. I personally have never seen anything like a wobble coming down at full speed.

I've observed more wobble on descent than on ascent but I don't find it troubling.  If you're flying the drone and not just doing a straight descent I think it's very stable.  RTH can be a little wobbly but I chalk that up to location correction.

jsparks349@gmai Posted at 2016-8-27 04:26
It's called Vortex Ring State and your fortunate that it never happened before if you descend straig ...

VRS is a thing of the past for Phantoms.
DJI designed the P3 and P4 with canted motors and restricts the descent speed to get rid of the risk of VRS.
Descending vertically is completely safe.

Snowwolfwarrior Posted at 2016-8-26 17:49
Sorry for the English language, "A right wobble on" means a bad wobble, :-)

LOL..   I should have known..   My wife and her family all immigrated from Scotland.  I'm familiar with the lingo

Hello everyone,

So i did the IMU calibration, tried a different set of blades and still the slight wobble. Luckily enough i have another P4 pilot and we usually fly side by side. His drone does eactly the same thing on decent. It is not enough to destabilise the gimbap though. So i suppose this is normal based on flying conditions... pushed it to max decent and its still alive. Happy flying!

mobeen.emmamall Posted at 2016-8-27 16:36
Hello everyone,

So i did the IMU calibration, tried a different set of blades and still the slight ...

Aloha mobeen.emmamall,

     DJI-Ken and labroides have it right.  When jsparks referenced

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

The mention of quadcopters is my edit.  You can check in the back pages of Wikipedia.  It was a battle to get it recognized by the full-sized copter pilots, but they caved at the argument of Physics of Scale and the videos of quadcopters going into and controlled exit from VRS.

     As noted by Ken and labroides wobble on descent is caused by something other than VRS because DJI has designed it out of the equation since the Phantom 2 (v.3).

Aloha and Drone On!