Altitude gain while using level button

[rvator51]

After engaging the level button, my RV will slowly gain about 100 feet altitude every couple minutes. It’s not clear to me what adjustment I would use to keep the airplane altitude the same while using the level button. has anyone encountered this and what did you do to solve it?

 

[Rhino]

Have you followed all the steps in the autopilot tuning guide?

What modes are you using?

 

[Marc_J._Zeitlin]

After engaging the level button, my RV will slowly gain about 100 feet altitude every couple minutes. It’s not clear to me what adjustment I would use to keep the airplane altitude the same while using the level button. has anyone encountered this and what did you do to solve it?

I won't say "RTFM", because some folks get touchy about being asked to read the documentation for the complicated equipment they're using (see previous invocations of "Read the Manual" responses in many other threads), but from the Skyview Pilot's User Guide, Revision P, Chapter 8, Page 8-1, it says, under "Level Mode":

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.​

So your system is doing exactly what it's supposed to do - maintain a VS of "0". It's not closing the loop on any particular altitude, so your altitude may float a bit, either up or down.

If you want to hold an altitude, use the ALT button, not the LEVEL button.

 

[SV_Classic]

I won't say "RTFM", because some folks get touchy about being asked to read the documentation for the complicated equipment they're using (see previous invocations of "Read the Manual" responses in many other threads), but from the Skyview Pilot's User Guide, Revision P, Chapter 8, Page 8-1, it says, under "Level Mode":

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.​

So your system is doing exactly what it's supposed to do - maintain a VS of "0". It's not closing the loop on any particular altitude, so your altitude may float a bit, either up or down.

If you want to hold an altitude, use the ALT button, not the LEVEL button.

Why would you type such a useful response and ruin it with nonsense the first half-paragraph?

It sounds like there's a preset gain value somewhere that isn't recognizing the drifting altitude even though it is supposed to be maintaining zero vertical speed? If you interpret "zero vertical speed" in an absolute sense, climbing at any rate isn't what it's supposed to be doing. No?

 

[Rhino]

Why would you type such a useful response and ruin it with nonsense the first half-paragraph?

Because too may people come here with questions without reading the manual. That's not all that unusual with any consumer product, but it can get irritating after a while. Marc was actually a lot nicer than some responses you'll see here.

 

[SV_Classic]

"Too many", as if it's up to you to decide which of Dynon's customers to be rude to. Not everyone here designed and built their avionics installations and troubleshooting an existing system is harder for a new owner than the builder. A shop I was talking to today expressed exactly that. I'm sorry it's such an imposition on you, all of these people asking questions you can't simply scroll past.

 

[Marc_J._Zeitlin]

It sounds like there's a preset gain value somewhere that isn't recognizing the drifting altitude even though it is supposed to be maintaining zero vertical speed? If you interpret "zero vertical speed" in an absolute sense, climbing at any rate isn't what it's supposed to be doing. No?

No. Maintaining zero vertical speed (the derivative of altitude) is not the same thing as maintaining a specific altitude. Hit a vertical gust (even a very weak one), and you may rise or sink some. The A/P will still, wherever you end up from the vertical gust, attempt to maintain zero VS, but at the new altitude. It doesn't know where you were when you pushed the LEVEL button, as is explicitly stated in the manual, and it doesn't care. If YOU care, then push the ALT button after you've had the A/P recover from whatever attitude you were in that you didn't like that caused you to push the LEVEL button.

 

[SV_Classic]

So it doesn't actually maintain zero vertical speed, it just tries to in between displacements from level that it may or may not register.

I don't have an autopilot in my personal ride, just chimed in because it's interesting. Different flight control systems approach the task of flying the plane differently. I've seen similar modes in other systems but I wouldn't call it something anyone routinely uses. You're usually either maintaining a set altitude or climbing/descending to an altitude.

 

[Marc_J._Zeitlin]

So it doesn't actually maintain zero vertical speed, it just tries to in between displacements from level that it may or may not register.

Which, if one reads the manual, one would learn without having to ask someone else to do the work for them.

People do NOT mind answering questions. What they mind is being asked to do work for folks that aren't willing to put in a modicum of effort themselves.

Now, if the question was "I looked through the Pilot's User Guide but I couldn't find an explanation of how the LEVEL button works - can someone point me to it if it's in there, or explain the use model if it isn't?", that would have been completely fine and reasonable.

Do you see the difference?

 

[Rhino]

"Too many", as if it's up to you to decide which of Dynon's customers to be rude to. Not everyone here designed and built their avionics installations and troubleshooting an existing system is harder for a new owner than the builder. A shop I was talking to today expressed exactly that. I'm sorry it's such an imposition on you, all of these people asking questions you can't simply scroll past.

I wasn't being rude to anyone. But apparently you are. Maybe you should simply scroll past.

 

[PaulSS]

VS 0 is exactly that, not Alt Hold. If you have a VS of 0 plugged in but hit mountain wave (for instance) you're going up (or down). The A/P may well stick the nose down to try and maintain a VS of 0 but you'll still go up. With Alt Hold the A/P will adjust your altitude and descend to the selected altitude, instead of just trying to maintain a VS of 0.

If you don't understand, RTFM

 

[airguy]

Sounds like a good place for a decent helping of RTFM.