Is it possible to have the Dynon Autopilot in a Vertical Speed zero mode, where I don't care about the actual altitude and just minimize altitude changes, ie maintain close to VS 0 fpm? I've read this mode may be useful in bumpy air but could not find the answer in the docs.
VS 0 mode
- Thread starter ve0kog
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Marc_J._Zeitlin
Active Member
Yes. If you push the "up" or "down" arrows when at some altitude to start a climb or descent, and then push the opposite to set the VS to 0, you'll get what you're asking for. I've never tried to see if it's better in turbulence - the AP certainly has some instabilities when in moderate chop when in altitude hold mode - maybe just trying to zero out VS would be smoother. Let us know what you find out.
I don't know if VS is available in Simple Mode (I've never looked, since I've used Expert from day one) but, if it is, it is just a matter of pressing the VS button. The mode changes to VS and it preselects zero.
I use this sometimes for exactly the reason you state. With a very light aircraft and a thermic day, I find that Alt Hold can be trying too hard to do its job and makes some quite large attitude changes. No criticism of the autopilot, it's doing what it's supposed to. You can, of course, adjust the settings so it is less aggressive and will correct more slowly but VS 0 in these circumstances works well.
I use this sometimes for exactly the reason you state. With a very light aircraft and a thermic day, I find that Alt Hold can be trying too hard to do its job and makes some quite large attitude changes. No criticism of the autopilot, it's doing what it's supposed to. You can, of course, adjust the settings so it is less aggressive and will correct more slowly but VS 0 in these circumstances works well.
porterjames
I love flying!
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- Sep 26, 2016
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I have tried to have the autopilot replicate what the pilot does in rising/descending air currents. Rather than try to maintain an altitude, accepting the updrafts/downdrafts will usually equal out altitude wise by the time you reach your destination. Especially on a long cross country you get the best average speed and economy. I prefer using a preset air speed on the autopilot. It does not replicate hand flying but it takes a lot of the work out on a long cross country.
airguy
Well-Known Member
The straight/level button may also be useful for this, it doesn't care about the actual altitude value, just levels out.
Marc_J._Zeitlin
Active Member
Is that true? Does it just essentially set VS=0, or does it set Altitude=<here>? Never played with that much...
airguy
Well-Known Member
From the FM, (Users guide, revision K, bottom of page 8-1) 
"The autopilot’s Level Mode (or Straight and Level Mode) will immediately attempt to reach zero
vertical speed and a roll angle of zero. It will not attempt to fly the aircraft to any previous
altitude or track and it will not respect any bug inputs. When activated, Level Mode will cause
the autopilot to engage if it was not already engaged."
Unfortunately for the OP's purpose, this eliminates any heading control which probably will be undesirable. I think the first suggestion of selecting vertical speed on the autopilot and setting that to zero would work better, as it also allows heading or nav functions to be used for directional control.
"The autopilot’s Level Mode (or Straight and Level Mode) will immediately attempt to reach zero
vertical speed and a roll angle of zero. It will not attempt to fly the aircraft to any previous
altitude or track and it will not respect any bug inputs. When activated, Level Mode will cause
the autopilot to engage if it was not already engaged."
Unfortunately for the OP's purpose, this eliminates any heading control which probably will be undesirable. I think the first suggestion of selecting vertical speed on the autopilot and setting that to zero would work better, as it also allows heading or nav functions to be used for directional control.
Last edited:
RVDan
I love flying!
You don’t mention what aircraft, but in the Exp world we just tune the AP to get the desired Alt hold result. You need to find a happy place between calm air and turbulent air. It will hold altitude plus or minus 25 ft in calm air and when tuned reasonably, plus or minus 150 ft in moderate turbulence. You can adjust it to hold tighter tolerances in turbulence but it will be a rougher ride.