Tuesday 24 October 2017

INAV Basics - Flight Control Boards

October 2017 - Betaflight is the most recent firmware for flight control boards (FCBs) and INAV is the GPS enabled
re-write of Betaflight which also caters for fixed wing models.

All the setup is done using the iNav Configurator. Works on PC and Mac as long as you can locate the correct drivers for the board you have. All the information on INAV is kept in the INAV Wiki on GitHub

I'm quite new to all this auto pilot stuff and there is a steep learning curve, so I thought I could pass on what I have learned so far.

So far I have experience with the Paris Sirius AIR3 F3 board with GPS from Multiwiicopter
Omnibus F4 V1 board
Matek F405 Wing
Matek F411 Wing
Ublox Neo M8N GPS module

The value of the AIR3 board is that it comes mounted in a gel damped housing with all the connectors and GPS sensor, and it's pre-loaded with the latest stable iNav firmware. Most of the tricky stuff is already done for you.

The AIR3 is an F3 board and doesn't have a built in OSD, but an addon OSD is available. The AIR3 OSD is configured using the MWOSD Chrome App, and partially by using your transmitter sticks.

If you're handy with a soldering iron and want to do it all yourself, you can follow Matt Ogbourne's video series on the Omnibus board setup. You will have to do all the soldering, firmware flashing and setup yourself. The Omnibus F4 does have a built-in OSD, which is configured in the iNav Configurator.

UPDATE 2018: The Matek F405 Wing and F411 Wing boards have changed the game. They are dedicated fixed wing boards with more servo outputs and a built in BEC specifically for servo power, as well as separate filtered BEC's for video, RC receiver and other gear.

Servos, Camera / VTx and receiver can be powered straight from the board.

A quick tip for soldering on the battery and ESC plugs. Silicon covered 16AWG is the best size wire, 18AWG is OK for low current light weight planes, but 14AWG is a bit too thick and difficult to solder onto the pads.

Power supply for non Matek Boards
The connections to FCBs are a little more tricky than normal ESC/receiver/servo connections because FCBs are more sensitive to incorrect or fluctuating voltage supply. With voltage spikes, FCBs can shut down, brown out or reboot causing total loss of control of the model.

It is highly recommended that the board and servos are powered by an accurate and stable 5.0V BEC like the AIR3 INAV BEC. You need to make up a power distribution cable so the BEC can plug into the board, and power the servos separately. As the 5.0V is being supplied to the FCB by the BEC you must disconnect the 5V line (red wire) from the ESC. Not a good idea to have two power sources for the FCB. Then all the signal wires from the servos and ESC connect to the board. The ground wires can either connect to the BEC or the board.

Another recommended precaution is to plug a voltage smoothing capacitor into your FCB, like this 3300uF 25V from MultiWiiCopter. The capacitor connects to any spare output pin-set across the power and ground pins, and absorbs any voltage fluctuations. Can also be plugged into receivers for added safety.

If you want to live dangerously you can just plug the servos and ESC straight into the board. like you would with a receiver, but you are only one voltage spike away from a crash.


  1. Andrew
    Another great informative write up. Now just have to get OSD going and I will feel much more comfy.
    This will give me time to get the pixhawk going over 3/4g and take a good long flight down the coast. Thanks you've been one of the most helpful in my conversion from quad to wings.Which I used to fly a lot 15 years ago, but unlike a bike, you can not just jump straight back into it.

  2. Hello Andrew. I am so pleased I found your site, it is a mine of information. I live in UK and am 70 this year and my main hobby is sailing but I dipped into RC flying soon after I retired about 10 years ago. I gave it up because I became so dispirited with may crashes with balsa models but your construction methods have given me new enthusiasm and inspiration to build your pusher trainer. Thanks so much for all the info, you spend all your waking hours compiling this info, well done keep up the good work

  3. does the Launch Assist Mode needs gps?

    1. No it doesn't need GPS, in fact I have an older version of the AIR3 iNav board just for launch assist and stabilised modes without GPS.

  4. Thank you for your help videos fs 6 radio I set up my flaps w/1 ch only
    It works I watched you do useing
    2 CHS.i would like to tell you how I did it useing switch c I have 30% and 100% and 0% on c.ch.but I couldn't figure out how to do a throttle off
    Switch w/o.your video on how to....
    Jeff b. Seattle,wa.

  5. I am a bit confused here my opterra 2kg wing ditched when using launch mode. The motor tail section broke off. Looks like it starts to spin to late and lacking power. Also in horizon mode the plane is going down in the pitch. How do i alighn in the inav fw if it losses altitude do i go minus or plus in the pitch alighnment.

    Thanks in advance

    1. Greetings. You need to manually set the throttle stick before throwing and the delay is preset but can be changed. I have decided Launch assist is not as good as normal power up then side arm throw.

      To align the board for horizon mode, prop the nose of your plane up about 5º then check the pitch value in the Setup page (first page) Then go to the Configuration page and change the Pitch Degrees (dont know if its plus or minus) Save then go back and check the Pitch value again in the setup screen. Keep adjusting till it is zero.

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  7. Is there a trick to get vbat working i soldered vbat on the hero32 but if i choose main voltage in osd.menu it say's 25V i can't adjust it. I fly 4S maybe you can come to the rescue again.1😁

  8. Strange things happen. I have to turn fc voltage off in osd settings to get correct vbat readings.........and had to set vbat scale in inave from 200 to 110.

    The manual states that you have to turn fc voltage on in osd menu....strange

  9. Hi,
    Andrew, hoping you could help me with what would seem simple for some but I've seemed to be stumped on regarding INAv setup on a wing. I've been trying to research how to setup rate profiles via switch on my QX7 to fully control my PIDs setups as a whole I.e 3 POS with different variables to test but so far all I can find online all mighty google search is a comment saying rateprofile no longer available since 1.6Inav in some sort mentioned. But nothing explaining what replaced it or how to go about doing a similar action on current Firmware. Do I need to just setup regular rate mix on my Qx7 or can I still do it via configurator? Hopefully it's not just a CLI configurable feature. Thanks for your time and truly enjoy your content.


    1. Thanks Rome. Sorry I can't help with that. I have not tried different PIDs for fixed wing. The advice I have read says to leave them alone for fixed wing flying.

    2. Thanks Andrew for the reply anyway. Yeah I heard that advice too about not messing with default PIDS. Bit it seems without some form of PID tuning in INAV getting a Wing to cooperate in any Navigation_Fw mode in a reliable sustainable flight fashion is pretty hard to dial in I guess. Thanks for your time again and I look forward to your future content.

  10. Hello Andrew,
    Quick question, my opterra fly's strait and level in pass true. It was flying straight and level without any FC. But now when i am in horizon mode it dips it's nose a bit. Like flying bunny hopping. Do i go negative or positive in inav with the pitch alighnment???? Can't figure it out

    1. I had to check mine again. You need to add positive pitch degrees to the Board Alignment to lift the nose in flight. I have about 5 for my Bixler and might have been 8 or 9º with the Teksumo