I tried to move my flight mode to Altitude holder when I was flying but when I around 2 meters from the ground the drone tries to land.
When I give some more power to adjust the altitude, the drone jumps like there is a bad reading of the sonar but I checked the logs and it seems to be good.

Do I have too much noise on the accelerometer ? Do I need to tune the altitude PID ?

Flying in stable mode is good

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Any idea? nobody?

Cover the baro with BLACK dense foam !!

I have exactly the same and could not yet find a solution.

Too many unknowns about your setup. Is your barometer correctly covered so that its shielded form light and wind/prop wash? You say you have a sonar. Is it setup correctly? 


Go through all these: 


Hi Chris
Installed exactly following the Sonar instructions, including shielded cable etc. Sonar is mounted on a large Y6 on a carbon arm away from prop wash. Also isolated against accustical noise from the motors with some side-mounted foam (as on Marco Robustini's Octo as seen in the 3.0.1 announcing video, leaving of course downwards view free, just in case you would ask :-).

Baro is factory made covered in the APM 2.5 case and in addition is below a top plane on which a GPS antenna with a quite large cooper ground plane is mounted which gives, as a side effect, also full shade to the baro (as recommended by Microcopter Germany).
Log's show no strange readings.
This is why I do not know where to search any more. 

I have read this few days ago and I get the same result. On concrete, my quad do not move, on grass, it is jazzy....

Comment by Thor Larsen on December 10, 2012 at 6:05am

Funny about flying over grass... I have yet to fly my 3DR quad, but I have been tuning a good deal in my office (with carpeted floors).  When sitting on my desk, motors running or not (no propellers attached), the ALT readings seemed to be very constant at .2m.  However, when I put the quad on the carpet, the readings would jump all over the place and the VSI would climb/fall like crazy and the ALT would (generally) start climbing slowly.  I moved it to a hardwood floor, and all those issues went away again (motors running or not).  Now, this is in no way scientific... but those readings and observations occurred before I read this thread (in fact, let me to this thread).  I have standard wiring, etc... will upgrade those soon.  seen here

Nobody in this big group who has an creative Idea where to search further?

I have an octo that I flashed with 3.0.1 firmware. If I disable the sonar, altitude hold is quite good.  

When I enable sonar I can see the sonar work in CLI.  It reads from 20 cm up to 75 cm.  For testing the sensor is mounted upside down and reads the 6 feet to the ceiling as 75 cm.

 In the Flight data screen Altitude does not change with sonar only the barometer. The Altitude reading changes when I open and close a door of the shop but not when I move my hand over the sonar sensor.

Flying in altitude hold with sonar enabled is very bad, the altitude has a mind of it's own.  The joy stick does have some effect but not much.

Anyone have an idea what the problem is??


Have you tried turning down SONAR_GAIN at all?

I've turned down to .01 and up to .5 and saw no change in the up and down very fast changes.  The sonar is working but the FC does not seem to use it even though it is enabled.

I have the octo flying well in Altitude Hold and loiter if I don't enable sonar.


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