Climbing using IAS

[Janekom]

I have two 10 inch Skyview Touch and an AP panel With Knob Panel. Recently I have tried to climb to altitude using the Autopilot and a set IAS. I selected the altitude, click on IAS on the AP panel, but the could not find the IAS label on the left hand knob.

When I descent on the other hand, I select the altitide I want to descent too, select VS on the AP Panel and then go to the VSI label on the left hand knob and adjust it. No problem.

I am sure that I am doing something wrong but cannot see what?

 

[Rhino]

Are you using simple or expert mode? You also appear to be mixing modes. Do you want IAS descent or VS descent? Your example uses IAS to climb, but you're selecting VS in your descent procedure.

 

[Janekom]

Thank you Rhino. I am using Expert mode. I would like to use IAS for climbing and VS for descending. I do not understand what you think I am mixing modes?

 

[andresmith76]

I think what you are needing is to add the IAS bug to the pop up menu when a button is pushed (opening the BUGS Knob Function Menu). This procedure is explained in section 4-3 of the Pilot's Users Guide.

 

[Rhino]

I was under the impression you wanted to do the same thing for climbs and descents, so thanks for straightening that out. In addition to what Andre posted, you might also try looking at page 9-3 of the User Guide, revision AC_v16. Touching Region 1 (airspeed indicator) on the screen should activate the IAS bug.

 

[Janekom]

Thank you André and Rhino. Before I sw your replies I have watched the Dynon video on this again. This one Skyview video

Watching from about minute 17 it behaves the same as mine where it will capture the current IAS and it will also show in the IAS window. But then the IAS bug is not available on the knob. So I think it is like André says - the bug has been turned of by me or someone else by accident. I will check when at the aircraft again.

Once again thank you

 

[airguy]

Perhaps you'll have better luck than I did, but when climbing in IAS mode my aircraft porpoises quite a bit as the autopilot "hunts" up and down around the target airspeed. It is not a smooth climb. I just use VS speed in the climb as adjust the rate as I go up and the airspeed starts to fall.

 

[lancair360]

Autopilot can be tuned up HOWEVER airspeed climb hunting on AP has been an issue in every plane I’ve flown over the years with the exception of the 737. We always would go to VS or pitch hold.

I’ve returned my setup and IAS climbs are okay, not great. Overall I say it’s a glitch in the matrix and not Dynon.

 

[Marc_J._Zeitlin]

Autopilot can be tuned up HOWEVER airspeed climb hunting on AP has been an issue in every plane I’ve flown over the years with the exception of the 737. We always would go to VS or pitch hold.

I’ve returned my setup and IAS climbs are okay, not great. Overall I say it’s a glitch in the matrix and not Dynon.

Interesting. I've been performing some glide tests recently and using IAS mode for both climb and descent. On a calm day, the IAS mode will hold +/- 3KIAS in the climb, and within +/- 1 KIAS in descent. This in a COZY MKIV. In turbulence, pitch control (IAS, VS, Altitude) sucks, though - the plane's all over the sky, and if it's turbulent enough, I just hand fly altitude. I've tuned the A/P back when I was on 15.4.7 - no idea if it would be better on V16.

 

[lancair360]

Interesting. I've been performing some glide tests recently and using IAS mode for both climb and descent. On a calm day, the IAS mode will hold +/- 3KIAS in the climb, and within +/- 1 KIAS in descent. This in a COZY MKIV. In turbulence, pitch control (IAS, VS, Altitude) sucks, though - the plane's all over the sky, and if it's turbulent enough, I just hand fly altitude. I've tuned the A/P back when I was on 15.4.7 - no idea if it would be better on V16.

Oh yeah, shoulda mentioned, descent always works better than climb in all the planes.

 

[Marc_J._Zeitlin]

Oh yeah, shoulda mentioned, descent always works better than climb in all the planes.

Interesting again. I wonder why that would be. I know that in tractor airplanes, thrust is destabilizing and in pushers (aft pushers, not on top) thrust is stabilizing, but I have no idea whether that holds true for airplanes with jets on the wings. In any case, I've got a COZY MKIV canard, so I would think that maybe pitch stability would be a hair better with the engine pushing than when gliding, but apparently not .

 

[CanardMulti]

Interesting again. I wonder why that would be. I know that in tractor airplanes, thrust is destabilizing and in pushers (aft pushers, not on top) thrust is stabilizing, but I have no idea whether that holds true for airplanes with jets on the wings. In any case, I've got a COZY MKIV canard, so I would think that maybe pitch stability would be a hair better with the engine pushing than when gliding, but apparently not .

Perhaps the solution, then, is an airplane with a propeller on each end. I've routinely used airspeed mode for both climbs and descents in my Defiant with excellent results, less than 1 to 2 kt speed drift, max. And that's without running the manual's AP tuning procedure. A typical cruise climb for me is 120 to 135 kt, depending on how far I'm going and how smooth the ride.

Ken

 

[lancair360]

Don't try and figure it out, you won't. Piston, turbine, jet, all have these quirks.

 

[wilkersk]

I was taught to bug AS for climb and VSI for descent. Outside of AP tuning, I wasn't aware this was an issue.

 

[rjones560]

Autopilot can be tuned up HOWEVER airspeed climb hunting on AP has been an issue in every plane I’ve flown over the years with the exception of the 737. We always would go to VS or pitch hold.

I’ve returned my setup and IAS climbs are okay, not great. Overall I say it’s a glitch in the matrix and not Dynon.

I agree with you on using IAS to climb. In really smooth air it will work ok, but in the slightest turbulence it will pitch up and down hunting the selected airspeed. This was true in all the corporate jets I have flown as well. It’s not just a problem with the Dynon autopilot. I usually use pitch mode in a climb and let the airspeed fluctuate a little.
Most experienced pilots refer to VS as “very scary” mode because most autopilots will will fly the aircraft right into a stall trying to hold the vertical airspeed in a climb. At least the Dynon autopilot has stall protection in this mode. Most of the older autopilots did not.