Altitude Loss During Loiter and Alt_Hold Flights

Hi All,

Managed to get my beast stable now when flying in Loiter and in Altitude Hold but I have noticed that in both of those modes, as soon as I start flying laterally, I lose altitude... significantly. Can anyone help me stop this from happening? My APM vibration levels are within the acceptable range, the APM is protected from Prop Wash and from gusts (foam covering) and the propellers are balanced. Not sure what else I can do to keep the altitude from dropping like it is....

3691094145?profile=originalThere was absolutely no wind today while flying so these rises and falls are quite tough to understand. The log file is attached and I thank anyone who can help with this issue in advance!


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  • Any resolution on this issue? I seem to be having the same problems and accel re-calibration did not help.

  • Just an 'out there' idea here, but what could be the effect of getting foam debris or dirt inside the baro chips case via it's vent hole ?

    I just wonder if anything tiny but significant getting in a rattling around might upset the chip from inside. 

    Also, I've had RF interference from my RC telemetry RX's back channel before, but I'm sure that's been documented elsewhere. I had to move one of the whisker type antennas away.


  • Developer

    I wonder if perhaps the logs rolled over (i.e. the dataflash filled up).  The parameter values are also not there.

    I think it is a vibration problem but not on the Z axis but rather on the X and Y, especially the X.  So as the copter leans over X and Y play a bigger role in the alt hold estimate.

    Another possibility is that the accel calibration wasn't done quite right.  If this is the case then you'll see the altitude climb a lot when you lean the vehicle over during a bench test (i.e. no motors running).

  • You using sonar and barometer? If your using sonar and you are not that high, then the angle when you pitch or roll changes making you seem farther from the ground and the altitude would adjust by lowering you. That's just a theory and assumes that the code base does not compensate for sonar/angle that the quad is at...

  • By the way, this was a 29 minute flight from motor on to motor off and for some reason, I only get 21 minutes reported in the log... Any idea why?

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