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G3X autopilot a bit aggressive

dbaflyer

Well Known Member
Today I had setup 3,000 feet and IAS 120 kts before take off. After takeoff and reaching 106 kts I engaged the AP. At this time the speed was increasing about 2kts every second so without the AP it would have been about 7 seconds to reach target airspeed at a fairly nice pitch attitude.

After engaging the AP, an immediate pitch down was initiated followed by a pitch up before holding at the IAS of 120 kts. I would call the pitch down and up fairly aggressive and really not necessary.

Am I doing something wrong?

Would have liked to embed the image here, but the the tag has quit working for me. Here is a bit of data from the log when the AP was engaged showing the pitch commands for the AP

[URL="https://photos.app.goo.gl/J5o2uQBL6HfFbu827"]https://photos.app.goo.gl/J5o2uQBL6HfFbu827[/URL]
 
Denis, if you had it set for IAS mode when you engaged it, the autopilot may have immediately put the nose down to try to get that 120 kias value, since your airspeed was still several knots below that at time of engagement.

Just a thought, anyway. I love the autopilot on the G3X but it?s got a lot of sophisticated functions and I?ve found it?s easy to inadvertently ask it to do something I don?t want! ;-)
 
Autopilot Gain Settings

Today I had setup 3,000 feet and IAS 120 kts before take off. After takeoff and reaching 106 kts I engaged the AP. At this time the speed was increasing about 2kts every second so without the AP it would have been about 7 seconds to reach target airspeed at a fairly nice pitch attitude.

After engaging the AP, an immediate pitch down was initiated followed by a pitch up before holding at the IAS of 120 kts. I would call the pitch down and up fairly aggressive and really not necessary.

Am I doing something wrong?

Would have liked to embed the image here, but the the tag has quit working for me. Here is a bit of data from the log when the AP was engaged showing the pitch commands for the AP

[URL="https://photos.app.goo.gl/J5o2uQBL6HfFbu827"]https://photos.app.goo.gl/J5o2uQBL6HfFbu827[/URL][/QUOTE]

Good Morning Denis,

Can you send us an email with the full datalog attached, as well as the autopilot gain settings you have programmed into your system? We can help to identify any shortcomings in the current system configuration, and work with you to improve the autopilot performance.

Thanks,

Justin
 
Denis, if you had it set for IAS mode when you engaged it, the autopilot may have immediately put the nose down to try to get that 120 kias value, since your airspeed was still several knots below that at time of engagement.

Just a thought, anyway. I love the autopilot on the G3X but it’s got a lot of sophisticated functions and I’ve found it’s easy to inadvertently ask it to do something I don’t want! ;-)

+1

If you were doing 106 kts and commanded a 120 kt IAS climb, you must expect the A/P to follow that instruction by dropping the nose to increase the airspeed and then start pulling up the nose once at 120 kts. Sounds like it did exactly what it was supposed to. I would expect it to see at 15 kt difference and drop the nose somewhat aggressively to give you what you asked for. When I ask my AP to do something, I expect it to do it now. If you don't preset the speed, the G3X will set the IAS climb speed to you current airspeed and then you can use the wheel to slowly match your desired speed. This would be a smoother transition.

Larry
 
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Yep, I've found that if I engage IAS mode with a target speed more that 2-3 knots from the current speed, the autopilot is pretty aggressive at getting to that new speed. Easiest way I've found to use IAS mode is to manually fly until you have the speed you want, then engage IAS mode at that speed. Or, engage it at your current speed and slowly roll in a few more knots at a time on your IAS setting until you get to your target speed.

I have the GMC 507 controller and I really like having that "knobs and buttons" option rather than using the soft menu within the G3X for AP settings.
 
Exactly

+1

Sounds like it did exactly what it was supposed to. I would expect it to see at 15 kt difference and drop the nose somewhat aggressively to give you what you asked for.

Larry

If you don?t want it to do that, then you need to manually match the speed you set it for, before engaging it.
 
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