ADAHRS Installation - Compass Calibration

[N951DZ]

We do not have a Compass Rose at my home field, nor is there one anywhere nearby. Apparently few of them are maintained/updated anymore. What procedure have you all used to accomplish the ADAHRS Compass Calibration called for in the Installation Manual?
My aircraft is an RV-12 ELSA with the ADAHRS installed in the Tailbone "roof" per the Kit Assembly Instructions.

 

[362PC]

Surprisingly with the systems we have on board you don't need a compass rose.

The process that was given to me by another avionics shop was:
- Find a place where you can taxi, a lot, in many directions and have room to point and roll for at least 100' or so
- using the ground track indication taxi so it matches 0° stop taxiing and hold position... calibrate north
- continue this process for each cardinal heading East, South, West.
- finish calibration on ground
- go fly and do in air calibration 360s

I was having all kinds of errors with xWinds and HSI readings. Once I did this process I am with in 1-2° of ADF numbers for runways and approaches.

 

[Carl_Froehlich]

I just put my trusty Boy Scout compass out on a wing. I buddy pushes the tail around to the four cardinal headings. Then do the air calibration. This process locks in the calibration promptly each time.

Carl

 

[PaulSS]

Just what Carl said; Boy Scout compass or iPhone, it just needs the 4 points and you can do that by pushing down on the tail and spinning it round. No need for an airfield compass rose. The air calibration gets it accurate.

 

[jakej]

Another method that is useful for those who have a fixed compass - use it as the reference & note what RV8JD says above.

 

[N951DZ]

Also, as the installation manual says:

"During the on-ground compass calibration it is important to perform the compass calibration in an area that has been verified to be magnetically neutral. The presence of steel reinforcement (rebar), electrical power lines under the tarmac, or other natural deposits of ferrous metals can result in an inaccurate compass calibration."

Right, I saw that also. From researching, it appears the whole point of a Compass Rose is/was to provide such a magnetically neutral area that is also surveyed/certified to be precise (more so than a small pocket compass). Apparently though since almost no one and few if any airports have one much less maintain them, I figured there must be a "modern" way of doing the ground calibration.

 

[N951DZ]

Another method that is useful for those who have a fixed compass - use it as the reference & note what RV8JD says above.

Thank-you All Above,
Looks like I'm trying desperately to make this too hard.
So if I understand correctly, the goal of the Ground Cal is to get close and then the in-air cal procedure fine tunes it to geographic North, etc.
I had been hung up on calibrating it precisely to magnetic North which, upon further reflection, would defeat the purpose of having all these electronics take care of it for me.
Thanks,
Dave

 

[Dynon]

It actually magnetic north you're after, not geographic north. All of the advice above is sound, with the caveat that local (ie in-ground pockets of magic rocks and such) magnetic interference can affect things.