Hi all,

First I'd like to say thank you to all of you who are giving so many useful tips and tricks in this forum. I read a lot here and learned much from you (at least I hope so).

Now my question: when hovering my P4 I noticed that it doesn't keep its altitude. For example it should stay at 1.2 meters after Auto take off. But it doesn't so. It continuously descends. If I wait long enough it even touches the ground. The barometer reading stays around 1.2 m but the VPS altitude indication decreases continuously down to 0 while descending until the aircraft has reached the ground. I also noticed the yoyo effect when breaking from a fast flight.

Everything else seems to function as it's supposed to. What shall I do? Just ignore?

I'm a bit scared to trust this device.

P.S. Forgot to mention that I use the latest software (2.8.3 on an iPad air and 1.1.411 firmware with updated batteries).

I have noted the same issue when using auto take off on P4, Think I've seen other recent post also.   Manual take off and hover at 4ft is stable with consistent height readings.   A quick test after upgrading to .411 gave a stable auto take off hover.

I find somewhat the same thing.  After takeoff, I always do a quick visual check of the P4 in hover, to assure the battery is in and charged, look for unusual vibrations and also check the control responses.  I always expect a slow decent when doing the check, so I simply apply a bit more throttle to adjust altitude, and it holds well after that.  I also find if cruising forward, if I let go the pitch stick quickly, the P4 will rise a meter or two as it stops, and settles to a height below that of the cruise.  To prevent this, I slowly release the pressure on the forward pitch to prevent a quick stop and fast reverse pitch (attitude) change, and the P4 holds the altitude very well.  In my case, I think the software is working well, but does have a margin of error during abrupt maneuvers and windy conditions.

j5255@yahoo.com Posted at 2016-6-13 03:59
I find somewhat the same thing.  After takeoff, I always do a quick visual check of the P4 in hover, ...

Well, what makes me a bit nervous is the discrepancy between the two meters. Additionally someone from DJI wrote that the VPS has priority over the barometer if the aircraft is near to the ground (but I can't remember where that was). To me this does not seem  to be the case. After doing some flights I also noticed that the barometer always shows a higher altitude than it is in reality.
The latter phenomenon  is described several times in this forum as a the yoyo effect.  The more I think about this I got the idea that there is something wrong with the barometer hardware.  And to me it looks like a serial error  not just a single one.

Hi Thomas and folks! Just found out this video from DJI about calibrating our VPS. I haven't tried it since I seem to have no problems yet with hovering and braking. Hope this helps.



Hans

Well, today I recalibrated everything (IMU, Gimbal, VPS and Compass) and nothing has changed. The aircraft continously descends and the barometer shows readings that are always higher than reality. Tried another flight with Litchi and when the P4 returned it showed something around 4m when in fact hovering at 1m.
From my experience as a pilot I'd say it's hardware, but I haven't had this when I received the bird about 6 weeks ago (at least I guess so).


Can the barometer unit be cleaned somehow?

I'm pretty desperated. Shall I send the aircraft back to DJI? Something I'd really like to avoid because I've heard their service here in Germany is almost next to none. And it takes time, too.

BTW, VPS measurment seems to be ok.

Thomas. Posted at 2016-6-14 17:50
Well, today I recalibrated everything (IMU, Gimbal, VPS and Compass) and nothing has changed. The ai ...

I've not seen it mentioned yet, but do you have a gimbal guard fitted to your aircraft ?

When I was observing the issue it was not a Optical/Sonic signal error.  The OAS height was correct at about 1.8 ft.  The height was showing 4.7ft. Several are calling  this a barometer height.  Does any one know for sure  this is from the barometer and not GPS height or some combination?

ShuanD Posted at 2016-6-15 01:11
When I was observing the issue it was not a Optical/Sonic signal error.  The OAS height was correct  ...

When you record a video, you can switch the subtitle feature on. There it definitely says it's the barometer value.

Aardvark Posted at 2016-6-14 18:57
I've not seen it mentioned yet, but do you have a gimbal guard fitted to your aircraft ?

No, I haven't. I read in the forum about the problems with gimbal guards. The aircraft is its original state except the firmware has been updated and of course recalibrated. Would it help to upload a flight log?

Thomas. Posted at 2016-6-14 18:36
No, I haven't. I read in the forum about the problems with gimbal guards. The aircraft is its orig ...

There's probably nothing to be gotten from the flight log, although the DJI tech's might make something of the DAT file from the aircraft.
Was this after 'auto' take of ?
I have the same setup as you and have not noticed this as yet.

Also have the same problem as do many others

Waiting for a fix

Aardvark Posted at 2016-6-15 02:00
There's probably nothing to be gotten from the flight log, although the DJI tech's might make some ...

It does not matter whether I use auto take off or take off manually.

rliamharpurb Posted at 2016-6-15 03:52
Also have the same problem as do many others

Waiting for a fix

In fact I have not seen somebody mention exactly the same problem in this forum.  I have seen many writings about the yo-yo effect.  But to me this does not seem to be the same because a constantly descending was not mentioned.  I'll try to call the technical service tomorrow and see what they will be going to tell me.

I have the same problem as you OP

I just sent my device to the German support. On the phone they confirmed that this problem has nothing to do with the yoyo effect. I'll keep you up to date.

People are mentioning the same symptoms on phantom pilots

We've all adopted new technology so hopefully all the bugs will be fixed eventually

But you would think altitude drop and the yoyo effect wouldn't exist as this was so right on previous crafts

Liam

Late to the party, but did you try calibrating the controller as part of your troubleshooting?

I've had this issue on a couple of P4s and  in my opinion it's due to bad IMU  sensors.

projeffrey11 Posted at 2016-6-16 11:15
I've had this issue on a couple of P4s and  in my opinion it's due to bad IMU  sensors.

OK, maybe, but isn't the barometer part of the IMU?

Lots of us have the problem (more than half from a poll I did on my FB group), waiting for FW up date, mine sometimes drops 6 meters, not flying it until it's fixed
Example of how bad mine is:

aerialphotograp Posted at 2016-6-18 06:05
Lots of us have the problem (more than half from a poll I did on my FB group), waiting for FW up dat ...

Gosh that is actually quite a lot of drop (Does that happen only on a side ways movement?)

@Thomas - Was this the issue with your drone also?

I will look out for this when I test flight my replacement brand new drone and let you know :/

BrianJ Posted at 2016-6-18 13:22
Gosh that is actually quite a lot of drop (Does that happen only on a side ways movement?)

@Thoma ...

Happens whichever direction I fly, even when hovering sometimes. Sometimes just a meter sometimes up to 8 meters

BrianJ Posted at 2016-6-18 14:22
Gosh that is actually quite a lot of drop (Does that happen only on a side ways movement?)

@Thoma ...

Yes Brian, that's exactly what I noticed, only that mine did not drop that much (at least I haven't noticed in flight). But therefore it did when hovering as well. And it started doing so right after take off. On some flights I didn't notice while it was on its way, but when it came back, just before landing, the barometer altitude said it was still up 5 to 8 meters, when it was 10cm above ground. And that really scared me ;-).

Thomas let me know the outcome

I have the same problems but no reply from any DJI rep

rliamharpurb Posted at 2016-6-20 04:08
Thomas let me know the outcome

I have the same problems but no reply from any DJI rep

Sure I will if you stay in the EU ;-) .  Didn't you try to call them?

FYI. The copter was exchanged and arrived this afternoon and after testing I determined that the problem still exists. It is exactly the same that I described.

What tests did their technicians do? Did anybody read my information and make appropriate tests?

I am not very satisfied with this device.

Thomas. Posted at 2016-6-29 17:05
FYI. The copter was exchanged and arrived this afternoon and after testing I determined that the pro ...

Hi Thomas, so sorry to hear you still have issues

Did you receive a brand new replacement? This is very strange you have a replacement with same issues? My replacement came from Holland factory and is operating fine.

Can you do a video with the this replacement showing your Dji Go app settings as your bird hovers and drops?

Maybe Dji Ken can help further somehow?

I have the same altitude problem with my phantom 4 really hope DJI can fix this like they fix the video signal problem previously that is much better now. Thanks

Thank you all for your sympathy!

I'll try to make a video and prepare flight data that show just exactly this problem. But maybe it'll take a moment ;-)
BTW, DJI is now asking to upload the flight log to the cloud. But they forgot to mention where in the cloud they want the file(s). Any ideas?

Factory reset followed by refreshing/updating the firmware, IMU calibration and sensor calibration has helped a lot of owners, mine is still far from perfect but much better after doing this.

Today I was finally able to prepare 2 videos and upload the flight data. As you can see in the video, the aircraft 1st ascends to 1,2m, then descends a bit before it ascends again. After that it slowly descends. At the end I landed it when it reached 0,5m, but still shows 1m on the barometric data.

Video showing the P4:
Video from the P4:
Flight log: http://healthydrones.com/main?share=SZqGqx

Mine is the same should I return to store?

rliamharpurb Posted at 2016-7-4 21:03
Mine is the same should I return to store?

From my point of view: No. The service here in Germany explained to me that they have big problems to calculate an exact altitude for a certain period of time. This is a known problem and in the next time it will not be fixed. Right now I don't have the time to write more about this but I have some ideas how to tell them that they must be wrong.

What I don't get is some people don't have a problem

A p3pro does not have this problem

So surely there is a problem?

In practice is this likely to cause any major problems ? In the video it takes a substantial time to drop. Perhaps it shouldn't do this, but it's unlikely that you will be hovering for this length of time. at 1.2m while filming. I'll do some checks on mine, I'm sure it will be similar, but as yet it hasn't caused any problems.

I think that when they ask for files to be uploaded then it is your choice what server to use, drop box may be one, then post the links here and they will pick them up. Or I'm sure you could pm the links to one of the Mods.

I find mine does this in the wind, as it fights to stay in place from moving sideways, it will drop slightly... once in a while rise up. I also noticed that my P4 will stabilize from this problem after my first battery cycle ( 2nd and 3rd battery when flying continuesly). Its weird, but I figure its calibration problem ( I read a thread yesterday about a factory reset ( in cycle of other steps )) has fixed this for some. I dont find it that big of a problem, as my other drone n drone exp has made this seem really stable and easy enough too cope with.

rliamharpurb Posted at 2016-7-5 03:43
What I don't get is some people don't have a problem

A p3pro does not have this problem

When I fly a longer distance it's the same. But then the barometer shows an altitude of several meters, even when the device is just 10 cm above the home point. And why are these people telling me it's a mathematical problem if others don't have it?

Yes. my altitude is off too, when I land I'm in the negatives most times, which also makes me think its a calibration error, which again others said a factory reset has fixed... I havent tried this yet as it doesnt bother me that much as I rely on eye sight rather then the sensors, but again thats me... when I do a firmware upgrade again n have to recalibrate, then I will go threw these step... I will find the page n post a link for u Thomas, tho you prolly already have seen it