Using the AP in HDG mode

[aglock]

Hi!

I'm just begining to try out the AP, and it is marvelous except for one item. We weren't able to produce acceptable results in the HDG mode. When engaged in curent heading it worked reasonable well but changing the heading for example 90 degrees to the right the AP initiates a turn to the right but have troubles to roll out on the correct heading. It always overshoots, tries to correct and ends up overshoort in the other direction. And it just keep doing s-turns. It also seems as the EFIS compass lags during turns.

Bank limit is set to 20 degres, and turn rate to 3 degres/s. Speed approx: 100 kts.

Any one who has a solution or have the same issues?

Best Regards, Andreas

 

[rvmills]

Andreas,

I've done a couple things to improve the HDG hold performance. The first was to re-cal the compass. After service at the factory, including a 5.0 FW update, on the first flight, the compass and heading both drifted a lot. A compass call fixed that, and that had the most dramatic effect on turns and HDG hold of the things I've done.

Since then, it's been mostly fine tuning the roll sensitivity, and in my RV-6, a setting of 6-7 seems to be the sweet spot, though I'm still fine tuning.

I also set the turn rate to 2.0 deg/sec, and with max angle of bank at 20 deg (like you have) it makes for pretty slow, gentle turns. But with those settings there is less overshoot and hunting on roll-out.

Hope this helps!

Cheers,
Bob

 

[aglock]

Thanks, we'll try that.

 

[dynonsupport]

An additional point while you're looking at your compass:

If the heading value swings when the airplane is pitching or rolling but _not_ turning, that will adversely affect HDG mode performance. A compass cal should help that.

 

[MauiLvrs]

If the heading value swings when the airplane is pitching or rolling but _not_ turning, that will adversely affect HDG mode performance.  A compass cal should help that.

Would a situation like this be exagerated by the compass not being physically aligned with the EFIS. ROll and pitch are rather easy to measure and set, but yaw is more difficult to get perfectly accurate.

 

[dynonsupport]

The main thing we are calibrating out when you do the cal is yaw- either mounting error or magnetic field error. In any case, a bit of yaw mounting error should calibrate right out.

If you are many degrees off in yaw, then you will start to see a fair amount of cross-coupling that can't be calibrated out, so you should still try and get it as close as you can.

 

[flyingforfun2004]

Hi Guys,

I too have see the same problem so ill recalibrate my compass too. What an amazing piece of kit it is.

I have been using it in trk mode and its fantastic.

Thanks Dynon for one hell of a Auto pilot.