Pitch Attitude unstable.

[Inverted]

I have a dual SV700 system. In level flight I am getting intermittently variations of +-2 deg. This happens on both PFD's similtanously when in compare mode. It also happens on both ADAHRS when in single mode.
Attitude in roll is rock solid ?

 

[airguy]

This can be due to rising or falling air in the atmosphere from localized heating. You can pretty much eliminate this as a factor if you take a test flight early in the morning before the sun has a chance to heat the ground and generate thermals in the atmosphere, or by flying very high (10,000'-12,000' or better, if you can get there).

The autopilot will attempt to maintain a level altitude at all times, and if the air outside is rising, then the airplane has to go nose-down to maintain that same altitude, which will also increase your airspeed. If the air outside is descending, you'll go more nose-up to maintain altitude, and airspeed will fall. Do you see any variation in airspeed during these changes in attitude?

 

[Inverted]

I should have clarified this before, this occurs in smooth and stable conditions with attitude set visually.
It is clear that the changes in pitch are erroneous, I thought I had a problem with an ADAHRS unit, what is strange though is when I tried to isolate which unit by changing the primary and standby ADAHRS and operating in single ADAHRS configuration the same thing happens on both ADAHRS ?

 

[Raymo]

What are you using for static air? Some have flush mount holes in the fuselage that do not provide accurate/stable readings.

Some of the certified units have to have the static air disconnected - essentially reading the pressure inside the cabin - to avoid this issue.

 

[jakej]

Inverted,
What aircraft type do you have?

 

[Dynon]

Can you take a video of your primary flight display and email it to us at support at dynonavionics dot com so that we can see what you're seeing?

 

[Inverted]

The aircraft is a RV7, I will collect some video for you....a picture paints a 1000 words as the cliche goes.

 

[jakej]

Have the symptoms been there from very first use of the system ?
How are the ADAHRS mounted ? Do you have a picture of them ?
I guess you used the standard Vans static port method ?

 

[Inverted]

Q1. No, it is a recent development, however the pitch has always been oversenitive in turbulence.
Q2. The ADAHRS are mounted within the recommended installation envelope just forward of the second bulkhead behind the baggage compartment, this position is approximately 4 ' aft of the centre of gravity.
Q3. I have the SafeAir Static system

It may be a week or two but I will send you some video and photos of the setup.

 

[jakej]

PM sent.

 

[RV8DR]

hello inverted,
i read your post and have the same problem in my rv8.
did you find a way to solve it.