Advice on altitude hold performance (screenshot)

[60av8tor]

Last evening I did the 6.0 autopilot in-flight tuning procedure.  It was perfectly calm, I made no changes to the default servo settings, and it worked really well..  This afternoon, I was flying home.  It was slightly turbulent - typical hot, southern afternoon.  While cruising at 4,500, the autopilot would kind of hunt for the altitude - up about 40', at times almost 60', back down about 20' below target of 4,500.  It really never settled in on altitude.  Honestly, I cannot remember if it was this way before - don't think so.  It was more than just the bumps; like it was continually climbing then descending - chasing the altitude.  I'm thinking I may need to increase pitch sensitivity..?

Separate question is the FD.  The FD is always slightly above the pitch bars as depicted in this screen shot.  Not really sure if this is normal or means an adjustment is necessary:

 

[60av8tor]

Dynon - any word on the screen shot above? I assume the pitch bars should be nested in the FD during AP flight w/ altitude hold on..?

I will do the pitch auto tuning again starting with the IAS hold procedure again - possibly increase pitch sensitivity. After that, looks like possibly increasing VSI gain during the altitude hold and capture procedure pt 2.

 

[Dynon]

The offset pitch bars are a bug that we'll be fixing with a small release shortly. If you have any flight angle pitch adjust dialed in to your setup, you'll see what you're seeing.

You're definitely on the right track with the alt process with the tuning guide. What are your numbers for alt gain / vsi gain currently?

 

[60av8tor]

The offset pitch bars are a bug that we'll be fixing with a small release shortly. If you have any flight angle pitch adjust dialed in to your setup, you'll see what you're seeing.

You're definitely on the right track with the alt process with the tuning guide. What are your numbers for alt gain / vsi gain currently?

Thanks for the reply, Dynon. I thought of the offset last night during my flight back to SC. Yes, I have -1' adjustment. I do remember reading about this in another thread. No offset adjustment on the FD, I assume - hence the update comment...?

I adjusted pitch sens from 10 to 12 and VSI gain from .6 to 1.2 - didn't adjust ALT gain. It worked well, but it was perfectly calm, so difficult to say. Maybe some ALT gain is in order...

 

[Dynon]

The FD should be auto-adjusting along with the degrees you've got dialed in, we just missed that in our development.

 

[knowlesbg]

Did 35 hrs flying venture not so long ago
What you experienced was mine also
Smooth weather no issue
Rough conditions I was chasing adjustments
Pleased to know Dynon will have a fix

 

[60av8tor]

Pleased to know Dynon will have a fix

May be misreading your post, but the fix will be to the FD not matching the AI if you have a pitch offset programmed (in my case, -1'). The fix for the autopilot performance came from going through the inflight tuning guide - several times in my case!

 

[led]

Hi Jon,

Couple of things to look at with altitude hold:

All of the following presumes that your servos aren't slipping.

First off, be sure that the IAS hold is working well - that sets pitch sensitivity and gain the most effectively.

Second, in smooth air,does the AP overshoot at all when leveling off at altitude?  If it does, consider turning ALT gain *down*. 

Third, if you are encountering big updrafts and downdrafts (as opposed to short sharp bumps), the AP can only correct at up to the vertical speed value you currently have set.  So if you fly into a 1000fpm thermal with the AP set to 500fpm, it won't be able to prevent some altitude change.  It doesn't help any that updrafts are usually paired with downdrafts, so the AP then has to deal with a big down while it's still correcting down.

That said, it'll be worthwhile to run through the turbulence tuning procedure on page 6-1 of the tuning guide. It can make a big difference.

Hope that helps!

 

[60av8tor]

It does help. Thanks, Lawrence!