Should I expect a crash at some point?

Nervously I took the Spy 750 Y6 up for the first time in over 3 weeks (had a warm spell of 25F today).

In stab it flies great, then switching to poshold it seemed fine, but did the twitchy thing again for a few seconds here and there, then seemed to smooth out (subjective). I brought it down and hovered nearby where it stayed rock steady for a minute or so and landed.

So, what does it mean when INAVerr goes to 255 and stays there? From what I understand it is the FC not receiving data from the GPS properly. Apparently this copter has done it from day one since transplanting the PIxhawk and running on AC3.2 and 3.2.1, with the 3DR GPS and the current CSGShop Neo-M8N. These errors did not exist on the Y6B with 3.1.5 and the 3DR GPS.

Any help is appreciated.

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Hi Dan,

Normal you don't know what INAVERR is as it is not documented anywhere

Randy , aswered that

The Inav errors mean The Inav errors mean that inertial nav has not received a GPS update within 0.3 seconds

Three discussions are discussing about this error reported in Performance Monitoring

occuring with 3DR GPS and M8N

giving details, logs, description of errors


Thorsten in one of them, who did use GPS's for Geomapping described two problems he observed :

-timing jitter (missing samples)

clock drift or communication latency between the GPS module and the Pixhawk.


But no reactions for any Dev ...I don't know why :(

If it is a false problem please tell us !

Well if INAVerr counts missed gps measurements, it would definitely increment every second with the strange quirk that Im observing on the m8n. However, less consistent, intermittent missed measurements could be a result of interference, which is a separate problem. In my opinion, apm needs to log and display the horizontal and vertical accuracy output of the ublox receivers which gives a much better indication of interference than DOP. I'll post about this in the GPS interference thread

Well, this might explain why the error climbs linearly but if this a not a problem then why log it as an error and if this error has such predictable characteristics then it should be reasonably easy for the devs to mitigate this by appropriate changes in the code....


This information is quite valuable, for instance, if the GPS dies, this counter will suddenly skyrocket, or if the GPS UART connection is flakey, you may get sudden intermittent increases, or if you lose lock at high attitude you could use INAVerr to confirm this. I think the first thing to do is to play with the M8N by itself, log the output and check the timestamps. Then, play with the configuration using the ublox tools to see if its a config issue. Then, if it seems like its just a quirk of the M8N, you could look at ignoring the consistent missed measurements in the code, but in doing so, you would risk detecting 'real' missed measurements.

I certainly wouldn't be disregarding the M8N though, csgshop have made a great product, I often get 15+ satellites during flight.


This error is also reported with 3DR ublox LEA 6H

some users have also seen with it INAVERR going to it max value of 255

I've been flying with a 3dr Pixhawk with 3dr GPS for a while without any INAVerrors and yesterad I made two flights with my newly built F450, on this one I have a M8N gps FrSky X8R receiver and during my two first flights yesterday I didn't have any INAVerrors.

My maden flight

I am getting similar behavior, which i posted about here:

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