Airspeed Calibration

[cjbouldin]

Hi
I just recently sent my D-10 for the D-10A upgrade and installed the Dynon Pitot/AOA probe.  After installation, I noticed that the Dynon airspeed is about 12 knots slower that the analog airspeed indicator.  The analog seems correct (formation flight checked).  

Is there a calibration technique other than the zero airspeed calibration (which I did)?
Is it possible that the 2 airspeed indicators sharing the same pitot line is having an effect on the Dynon?

Thanks

 

[RotaryLancair]

do they share the same pitot and static lines? if so, check for a leak between the analog and the Dynon. if they dont, there is probably a problem with the static port connected to the Dynon, assuming as you say, the analog is correct.
it would seem most all airspeed problems are due to static port placement.

 

[DBRV10]

I know this is a bit out of left field but TRIPPLE CHECK that you have the AOA connected to the AOA holes and the pitot hole is actually connected to the Pitot.

And check your static as well.

 

[cjbouldin]

They do share the same pitot and static ports and lines. I will check the connection between them. I also noted that the airspeed seems to occasionally "stick". It almost acts like a stuck dial on an analog gauge. For example, flying along at 154kts on the Dynon (the analog reads 165kts) and changing airspeeds slightly the Dynon "sticks" on 154 while the analog changes to 167 so. It will unstick and it's not consistent.

I'm just trying to determine wether its a static issue or an electronic issue.

Thanks

 

[dynonsupport]

There's an algorithm in the EFIS that makes the IAS seem resistant to very slight changes - this helps it be visually resistant to very fast fluctuations, but you'll only see this plus or minus a couple of knots around any particular airspeed. If it's unsticking and moving a dozen or so knots, then the first thing I'd suspect is water in the pitot line, upstream (on the EFIS side) of your split that forks between the EFIS and analog IAS. You can see if it's real by unplugging the pitot from the EFIS and using your finger to press on the pitot port. You should be able to increase airspeed relatively smoothly. Do the same with your mouth on the actual pitot, and see where the issue is.