Copter-4.0.0-rc6 available for beta testing!

Copter-4.0.0-rc6 has been released for beta testing and can be installed using MP’s or QGC’s “Beta Firmwares” link or alternatively the binary can be downloaded directly from .

The changes vs -rc5 are in the ReleaseNotes and copied below:

  1. Compiler updated to gcc 6.3.1 (2nd attempt) which resolves issue with KakuteF7mini firmware builds

So this is just a single change to update to a new compiler used to build the firmware. We thought this went out with -rc4 but sadly due to a technical glitch it didn’t so we’re trying again. We’re confident the new compiler is fine because most of the core developers have been using it for more than a year but still, as a general rule the final release candidate should be the same as the official release.

You shouldn’t notice any change vs -rc5 but all feedback is appreciated!

Thanks again for helping us with beta testing and unless we hit any issues in the next few days it is very likely -rc6 will become the official release.

By the way, we are looking for a video to put at the top of the release blog post here on and Facebook so if you have a video please either link it below or PM me, thanks!

Hey @rmackay9
I can make a video by Tuesday. What should video cover?
Thank you


What kind of video do you need?

@zhangsir, @Mallikarjun_SE or anyone else interested,

I’m looking for a video of a copter flying using Copter-4.0.0 (any one of the release candidates). Ideally either a pretty video and/or an informative one - i.e. flying in multiple modes or showing off a new feature. Normally Marco Robustini makes our release videos but his flying field is under construction at the moment.

@rmackay9 I have a full flight video using a K120 ultra-small helicopter, including an automatic mode video with PIP FPV perspective synchronously recorded content.

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@zhangsir, that sounds pretty good. Is it this video?


That’s right, this video can be shared to the official website!

Out of curiosity Where does 4.0.1-dev fall in the rc(x) timeline? I “accidentally” loaded this to my hex and its flying great…

Will the 4.0.0-rc(x) lead up to the 4.0.1 official build?


Copter-4.0.1-dev is ahead of Copter-4.0.0 (the official release). In general “latest” (aka the -dev build) is the “bleeding edge” meaning it has all the latest changes that the developers have completed but it hasn’t gone through any beta testing meaning that it is almost guaranteed to have bugs. Because of the careful code review process and vast amount of automated testing we do, those bugs are normally not too serious (i.e. won’t cause crashes) but we still recommend sticking with the official stable version or the beta version if you’re interested in helping us with beta testing.

It seems good so far. Haven’t done auto tune in it yet but I have configed dynamic notch tuning using the blheli32 esc rpms and taken it in the air about 1/2 dozen times testing it out

I did notice that the battery capacity on the monitoring page always goes back to 3300 mah. The only way to change it so it sticks is in the full parameter page

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Great, thanks for the feedback. I did a quick test of the battery capacity using MP’s Setup >> Battery Monitor page and it appeared to “stick”. Perhaps it’s been fixed in a very recent version of Beta MP. In any case, if you see the issue again especially after upgrading to the latest MP, we should raise an issue in the MP issues list.

Ok sounds good… I am updating MP almost daily now a days due to AC being ahead of MP

I will try again as I just updated MP today

Is there anything in particular you would like me to test in 4.0.1-dev on my Hex?


Thanks for the offer, Dijkstra’s is perhaps one area that very few have tested. So for example creating some complex fence shapes and showing it can around them would be nice. Sadly MP’s support of “complex” fences is a bit lacking so it might be necessary to use QGC.

Also we will be releasing Copter-4.0.1-rc1 in the next day or two so a general check that that is working will be good.