Heading's way off

[woneill]

The heading displayed on the SV700 is +15 degrees off when compared to mag compass+auto pilot+696+Foreflite, which all agree. This is the greatest deviation and it's when heading East or North. The other directions are less inaccurate.

I've recalibrated the ADAHRS 4 times in the last years and never get closer than 10 degrees when in flight.

I have always calibrated on the ground when taxiing and stopping when GPS signals are at cardinal directions.

Should I be doing this in the air for better accuracy?

Any suggestions appreciated.

 

[lindsayj]

For what it's worth: Make sure you're not near any metal buildings or heavy equipment or on top of reinforced concrete when you do your calibration. You have to be a couple of thousand feet away from that sort of stuff to make sure. I had some trouble until I did this. Jack L.

 

[mmarien]

IMHO I don't think the ADAHRS is that sensitive. I did mine on the rebar reinforced concrete runup pad. I marked the cardinal directions on the pad using Topcon RTK GPS. It's an accurate representation of magnetic direction and reflected in my calibration of the ADAHRS. I believe that if your flight path marker is on the attitude indicator, magnetic and GPS should coincide.

I had trouble when I first tried to calibrate which turned out to be the AN bolts I used to mount the ADAHRS. When I tried to calibrate the compass I only had two directions. With that in mind, I'd look a little harder for magnetic interference.

 

[mmarien]

Another thought. As mentioned on this forum before, the GPS direction isn't working until you are going fast enough. The outline on the map direction will turn purple when it is getting GPS direction. See previous post. Otherwise it's white indicating that it is magnetic compass direction. See below, 14kts and still magnetic direction.

A static rose on the ground is probably the best way to calibrate  the compass. I did mine with the engine, lights and avionics on.

 

[dabear]

Just making sure.... but you are aware that the 696 & forflight are giving you track direction, not heading?

When in motion and you have a cross wind, the GPS is going to give you a different "track" fromt the heading given by the ADHARS.

Bear