AP level button

[Mweaver6]

When using the AP if I select Level, the aircraft pitches down, and resumes level flight when disconnecting the AP. Other functions of the AP work perfectly if you select Trk/Hdg or GPS and vertical capture climb or descend lust appears to be Level button. Anybody experienced this

 

[HFMan]

Does it actually pitch down below the artificial horizon? Mine pitches to zero degrees, which is level unless your ADHRS unit is not properly leveled in the airplane. You also might look at "Flight Angle Pitch Adjustment" in the PFD Setup.

 

[Mweaver6]

Does it actually pitch down below the artificial horizon? Mine pitches to zero degrees, which is level unless your ADHRS unit is not properly leveled in the airplane. You also might look at "Flight Angle Pitch Adjustment" in the PFD Setup.

Yes it does enter a descend below the horizon. I have had to adjust the pitch angle on the efis to -8.5 deg to get the AI to level out when trimmed out to level flight when not using the AP. The brackets supplied to fit the adhrs appear to fit one way so not sure how it can be fitted incorrectl, unless it requires shimming

 

[HFMan]

That very well could be your problem (although I can't say with certainty, just guessing). If you have any means, I would try to get your ADHRS level when the aircraft is in level flight. 8.5 degrees sounds like an awful lot of correction.

 

[Eugr]

Per the manual, ADAHRS should be aligned with all 3 axis of the aircraft. That doesn’t mean it should be level when you are in level flight. Your pitch attitude in level flight depends on your airspeed and the plane design itself. Some airplanes are pitched a bit down in level flight at cruise speed.

You can set pitch correction in the menu to show level in normal cruise, but it‘s not necessary.

 

[HFMan]

But 8.5 degrees offset doesn't sound like it's aligned with the pitch axis.

 

[Eugr]

But 8.5 degrees offset doesn't sound like it's aligned with the pitch axis.

It doesn’t indeed. I have 1.7 degree difference and wondering whether I should shim it or not.

 

[DBRV10]

The AP LEVEL mode should hold the wings level in roll, and zero VS in pitch. According to the manual.

 

[HFMan]

This is also in the installation manual:

Mounting requirements for the SV-ADAHRS-200/201:
• Must be mounted within one degree of parallel to all three aircraft axes,
• The pneumatic fittings must face toward the front of the aircraft,
• The mounting tabs must be towards the bottom of the aircraft, with the label towards the top of the aircraft.

 

[Mweaver6]

I think I have found the source of the problem. The brackets holding the adahrs unit were fitted incorrectly and not in alignment. I still need to test fly, but with the brackets fitted correctly the correction to the AI is now -0.5 deg from the -8.5.
I will confirm once I can re test in flight. Thanks to everyone’s input