Altitude drops during flight...

[Kman]

I went to Apple Store and got another P4 this morning. Then I went to a field to fly (after firmware updates and IMU $ Compass calibration) to check if the new one has same altitude dropping issue. Unfortunately the answer is YES.

It is basically as same as the previous one. As soon as accelerate and I turn left or right, altitude drops and P4 goes forward but down as well even I don't touch left stick on controller. At that time I have to push left stick up to not to crash. That happens especially in Sport Mode and I cannot imagine I flying low over water.

Thanks for updating. Hopefully they fix it with a firmware update.

 

[G-K]

Thanks for updating. Hopefully they fix it with a firmware update.

Actually as a Phantom user (who also has P3P) I consider bring the P4 back, get refund and wait until these issues are solved. On the other hand it is very hard for me to leave better video quality with 120 fps, active tracking, tap fly etc. all of these features are very useful for me...

 

[G-K]

Many people flying craft with the Pixhawk flight controller notice a similar phenomenon. It has been attributed to a pressure change fooling the barometer, making the controller think it is higher than it really is. This is more pronounced as the speed increases creating a larger pressure change; hardly noticeable at walking speed and very pronounced a high speed. Don't know it this is the same issue with the P4. Is it speed dependent?

Do you think that can be fixed by firmware update?

 

[gtpark]

Yes it is speed dependent. I can notice much more on Sport Mode.

This could well be a design/hardware issue then. I don't know that software will be able to compensate if it turns out to be a pressure bubble impacting the accuracy of the barometric readings.

 

[John Locke]

I have a theory. I'm not sure how valid it is, but I'll share it. My P4 has exhibited this phenomena also. The air circulation of the craft is quite clever, and quite different than P3P. Air enters the belly of the craft using a fan, as we have all seen by now in photos. The air is pushed up through the craft, then out the motor pod vents. The air circulation through these vents is helped with suction created by the venturi of the propeller thrust racing downward over the top of the motor pod (I think that's so clever). When the rushing air is split by the motor pod arm, it's compressed slightly. As the air goes past the arm, it's uncompressed and speeds up, causing a venturi suction affect. This draft of the passing air helps by sucking air out of the motor arm bottom vents. My theory is the pressure differentials of this rushing air at different throttle levels is affecting the barometer sensor inside, causing the craft react with altitude changes, unpredictably. Turning left or right happens to amplify these pressure changes (negative or positive) because of the change in pressure from the craft spinning to turn. This could potentially change the venturi, and change in craft's interior barometric pressure, ever so slightly, affecting the accuracy of the barometer sensor readings. Again, it's just a theory.

 

[lfaitas]

I have a P3P and for about 2 weeks now also have a P4.
I also noticed a drop in altitude especially in Sport mode.
I usually fly over the sea so maybe it has also something to to with the sensors not working well over water .. altough gps signal is at max count.
Apart from that all and all i am happy with my new bird with all its new features.. especially the active tracking which is amazing..

 

[gtpark]

I doubt the barometer is impacted by whether the craft is over water or not.

 

[frankieo11]

First reduced battery life and range, and now this? Looks like I wont be getting a P4 until things are fixed/addressed. Yes build quality is better, but performance seems to be subpar compared to the P3P so far. Dammit.

 

[ianwood]

There are probably two different effects happening here. And it appears DJI's new design was not thoroughly tested for either.

The first is ground effect. When you are low to the ground, the pressure increases slightly as the air hits the ground and effectively becomes a cushion for itself.

The second is something seen more commonly on big custom builds using the A2 controller. In fast lateral flight, a high pressure bubble builds around the entire frame due to the increased downwash. The A2 should detect and compensate for this but it doesn't. Maybe they will add it to the P4.

 

[Humberto Caldas]

Hello everyone

My first entry in this forum and for a bad reason.
Im with the same problem , I had noticed in the first flights but had not given much importance , this is my first phantom thought it would be some kind of my mistake.
Today after read this thread I was flying and testing , and yes the phantom drops down +- 3 metros (+-10feets), the higher the speed falls further.
I noticed that also falls fly forward and stop, once in sport mode worse.

Im from Portugal i have buy the Phantom from DJI online shop and i dont real know what to do.

HC

 

[gtpark]

Hopefully they can address this with either a design or hardware change if they will admit to the issue.
This really limits the ability to scoot along close to the ground or water.

 

[rberga1]

Does the drop still occur with VPS off?

 

[Dronetwinkies]

is this the cause of vortex ring state?

 

[gtpark]

is this the cause of vortex ring state?

Vortex ring state is not related to this issue.

 

[TheEdge]

Does anyone have a video showing this effect? Some are reporting a 10' drop in altitude when banking left or right. That could cause a lot of issues if it is true. Would the flight logs not show this as well?

 

[robdigphot]

I have been experiencing the same problem as everybody else. My P4 drops about 9 feet after it slows to a hover. An example of this can be seen at the end of this short video clip.

 

[caseyb41]

I've noticed mine doing this, however this is my first phantom. So i was unsure if it was normal or what. Guess it's not.

 

[rockydog]

Has anyone contacted DJI and received a response regarding this?......Could have nasty implications if you're doing an overhead tracking shot, and go to hover over something -(or someone!) when you're close to them.

 

[robdigphot]

Has anyone contacted DJI and received a response regarding this?......Could have nasty implications if you're doing an overhead tracking shot, and go to hover over something -(or someone!) when you're close to them.

Yes, I contacted them on live help last night. They said that there would be a firmware update addressing this issue soon.

 

[rockydog]

Yes, I contacted them on live help last night. They said that there would be a firmware update addressing this issue soon.

Good news.....thanks for coming back on this.