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?

Edited to add more details to stop the RTFM police.

. Forum credentials: Long time forum member, former Dynon beta tester for D-10a, skyview and D3. I was flying the other day and decided to test out my level button, which I had never used. I normally fly my auto pilot in expert mode, and mostly use all the features of it on longer trips. After engaging the level button the aircraft would slowly gain altitude about 50 feet a minute over Several minutes until I turned it off. this happened on two different flights. I RTFM, then went to the installation manual and read all the auto pilot settings to see if something applied that I missed in the set up thing. I reviewed the Dynon auto pilot forum to see if this message had ever came up in the history. after not getting an answer from all three I posted thinking I was safe and it was a good question to ask. Clearly, I was wrong. I am going to continue to play with this in different flights and see if I can figure out why it is constantly gaining altitude. I would expect it to go up sometimes, go down sometimes, go straight sometimes for a period of time depending on what the Air is doing, that’s not the behavior I saw.

 

[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.

 

[rvator51]

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

What modes are you using?

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

Yes, I did all of the in-flight AP tuning steps and yes I did RTFM first, checked all of the AP settings, searched the Dynon AP forum, then posted; contrary to all of the good folk suggesting that I didn't, so they can KMA. I just thought it a little odd that with the AP LEVEL button engaged and the AP attempting to get to zero airspeed for straight and level flight, that my altitude would continuously slowly climb. I found nothing in the AP setup that mentioned this. I normally don;t use this mode but was just playing around with it on a short flight and noticed the climbing behavior. I guess the consensus is that this is pretty normal and expected behavior.

 

[rvator51]

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

What modes are you using?

Yes, I normally fly in expert mode, but I was just testing the level button out as I’ve never used it before.

 

[rvator51]

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.

I read nowhere in the manual or in the forums or in the set up that after engaging the level button(before I posted) , that the AP would slowly gain altitude constantly over a longer period of time. I just found that kind of interesting and wondered if other people had the experienced same phenomena, I would expect it to normally at least climb up and down a little bit instead of constantly climbing. I really thought this was a valid question for the forum, guess many people thought not.

 

[rvator51]

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.

I wonder if maybe because I was flying in the morning and getting thermals caused the altitude to slowly go up from in both flights that I used the LEVEL button. It seemed to be pretty ratable, about 50 ft./min. over several minutes and it happened on both flights. I found that a little odd I would expect more variance. It’s not a big deal. I was just playing with the level button as I’ve never used it before.

 

[Rhino]

I read nowhere in the manual or in the forums or in the set up that after engaging the level button...

I was just answering someone's question as to why some people respond that way. I wasn't making any judgements about what you posted.

 

[rvator51]

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?

JFC, OK you win, let me revise my post. Forum credentials: Long time forum member, former Dynon beta tester for D-10a, skyview and D3. I was flying the other day and decided to test out my level button, which I had never used. I normally fly my auto pilot in expert mode, and mostly use all the features of it on longer trips. After engaging the level button the aircraft would slowly gain altitude about 50 feet a minute over Several minutes until I turned it off. this happened on two different flights. I RTFM, then went to the installation manual and read all the auto pilot settings to see if something applied that I missed in the set up thing. I reviewed the Dynon auto pilot forum to see if this message had ever came up in the history. after not getting an answer from all three I posted thinking I was safe and it was a good question to ask. Clearly, I was wrong. I am going to continue to play with this in different flights and see if I can figure out why it is constantly gaining altitude. I would expect it to go up sometimes, go down sometimes, go straight sometimes for a period of time depending on what the Air is doing, that’s not the behavior I saw.